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register pressure. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@105501 91177308-0d34-0410-b5e6-96231b3b80d8
3696 lines
132 KiB
C++
3696 lines
132 KiB
C++
//===- LoopStrengthReduce.cpp - Strength Reduce IVs in Loops --------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This transformation analyzes and transforms the induction variables (and
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// computations derived from them) into forms suitable for efficient execution
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// on the target.
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//
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// This pass performs a strength reduction on array references inside loops that
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// have as one or more of their components the loop induction variable, it
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// rewrites expressions to take advantage of scaled-index addressing modes
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// available on the target, and it performs a variety of other optimizations
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// related to loop induction variables.
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//
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// Terminology note: this code has a lot of handling for "post-increment" or
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// "post-inc" users. This is not talking about post-increment addressing modes;
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// it is instead talking about code like this:
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//
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// %i = phi [ 0, %entry ], [ %i.next, %latch ]
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// ...
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// %i.next = add %i, 1
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// %c = icmp eq %i.next, %n
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//
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// The SCEV for %i is {0,+,1}<%L>. The SCEV for %i.next is {1,+,1}<%L>, however
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// it's useful to think about these as the same register, with some uses using
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// the value of the register before the add and some using // it after. In this
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// example, the icmp is a post-increment user, since it uses %i.next, which is
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// the value of the induction variable after the increment. The other common
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// case of post-increment users is users outside the loop.
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//
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// TODO: More sophistication in the way Formulae are generated and filtered.
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//
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// TODO: Handle multiple loops at a time.
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//
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// TODO: Should TargetLowering::AddrMode::BaseGV be changed to a ConstantExpr
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// instead of a GlobalValue?
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//
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// TODO: When truncation is free, truncate ICmp users' operands to make it a
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// smaller encoding (on x86 at least).
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//
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// TODO: When a negated register is used by an add (such as in a list of
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// multiple base registers, or as the increment expression in an addrec),
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// we may not actually need both reg and (-1 * reg) in registers; the
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// negation can be implemented by using a sub instead of an add. The
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// lack of support for taking this into consideration when making
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// register pressure decisions is partly worked around by the "Special"
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// use kind.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "loop-reduce"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Constants.h"
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#include "llvm/Instructions.h"
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#include "llvm/IntrinsicInst.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Analysis/IVUsers.h"
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#include "llvm/Analysis/Dominators.h"
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#include "llvm/Analysis/LoopPass.h"
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#include "llvm/Analysis/ScalarEvolutionExpander.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include "llvm/ADT/SmallBitVector.h"
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#include "llvm/ADT/SetVector.h"
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#include "llvm/ADT/DenseSet.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/ValueHandle.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Target/TargetLowering.h"
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#include <algorithm>
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using namespace llvm;
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namespace {
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/// RegSortData - This class holds data which is used to order reuse candidates.
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class RegSortData {
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public:
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/// UsedByIndices - This represents the set of LSRUse indices which reference
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/// a particular register.
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SmallBitVector UsedByIndices;
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RegSortData() {}
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void print(raw_ostream &OS) const;
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void dump() const;
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};
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}
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void RegSortData::print(raw_ostream &OS) const {
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OS << "[NumUses=" << UsedByIndices.count() << ']';
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}
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void RegSortData::dump() const {
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print(errs()); errs() << '\n';
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}
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namespace {
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/// RegUseTracker - Map register candidates to information about how they are
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/// used.
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class RegUseTracker {
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typedef DenseMap<const SCEV *, RegSortData> RegUsesTy;
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RegUsesTy RegUsesMap;
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SmallVector<const SCEV *, 16> RegSequence;
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public:
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void CountRegister(const SCEV *Reg, size_t LUIdx);
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void DropRegister(const SCEV *Reg, size_t LUIdx);
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void DropUse(size_t LUIdx);
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bool isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const;
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const SmallBitVector &getUsedByIndices(const SCEV *Reg) const;
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void clear();
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typedef SmallVectorImpl<const SCEV *>::iterator iterator;
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typedef SmallVectorImpl<const SCEV *>::const_iterator const_iterator;
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iterator begin() { return RegSequence.begin(); }
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iterator end() { return RegSequence.end(); }
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const_iterator begin() const { return RegSequence.begin(); }
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const_iterator end() const { return RegSequence.end(); }
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};
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}
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void
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RegUseTracker::CountRegister(const SCEV *Reg, size_t LUIdx) {
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std::pair<RegUsesTy::iterator, bool> Pair =
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RegUsesMap.insert(std::make_pair(Reg, RegSortData()));
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RegSortData &RSD = Pair.first->second;
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if (Pair.second)
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RegSequence.push_back(Reg);
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RSD.UsedByIndices.resize(std::max(RSD.UsedByIndices.size(), LUIdx + 1));
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RSD.UsedByIndices.set(LUIdx);
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}
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void
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RegUseTracker::DropRegister(const SCEV *Reg, size_t LUIdx) {
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RegUsesTy::iterator It = RegUsesMap.find(Reg);
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assert(It != RegUsesMap.end());
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RegSortData &RSD = It->second;
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assert(RSD.UsedByIndices.size() > LUIdx);
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RSD.UsedByIndices.reset(LUIdx);
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}
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void
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RegUseTracker::DropUse(size_t LUIdx) {
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// Remove the use index from every register's use list.
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for (RegUsesTy::iterator I = RegUsesMap.begin(), E = RegUsesMap.end();
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I != E; ++I)
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I->second.UsedByIndices.reset(LUIdx);
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}
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bool
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RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const {
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if (!RegUsesMap.count(Reg)) return false;
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const SmallBitVector &UsedByIndices =
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RegUsesMap.find(Reg)->second.UsedByIndices;
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int i = UsedByIndices.find_first();
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if (i == -1) return false;
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if ((size_t)i != LUIdx) return true;
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return UsedByIndices.find_next(i) != -1;
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}
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const SmallBitVector &RegUseTracker::getUsedByIndices(const SCEV *Reg) const {
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RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
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assert(I != RegUsesMap.end() && "Unknown register!");
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return I->second.UsedByIndices;
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}
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void RegUseTracker::clear() {
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RegUsesMap.clear();
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RegSequence.clear();
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}
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namespace {
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/// Formula - This class holds information that describes a formula for
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/// computing satisfying a use. It may include broken-out immediates and scaled
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/// registers.
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struct Formula {
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/// AM - This is used to represent complex addressing, as well as other kinds
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/// of interesting uses.
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TargetLowering::AddrMode AM;
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/// BaseRegs - The list of "base" registers for this use. When this is
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/// non-empty, AM.HasBaseReg should be set to true.
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SmallVector<const SCEV *, 2> BaseRegs;
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/// ScaledReg - The 'scaled' register for this use. This should be non-null
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/// when AM.Scale is not zero.
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const SCEV *ScaledReg;
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Formula() : ScaledReg(0) {}
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void InitialMatch(const SCEV *S, Loop *L,
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ScalarEvolution &SE, DominatorTree &DT);
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unsigned getNumRegs() const;
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const Type *getType() const;
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void DeleteBaseReg(const SCEV *&S);
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bool referencesReg(const SCEV *S) const;
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bool hasRegsUsedByUsesOtherThan(size_t LUIdx,
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const RegUseTracker &RegUses) const;
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void print(raw_ostream &OS) const;
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void dump() const;
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};
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}
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/// DoInitialMatch - Recursion helper for InitialMatch.
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static void DoInitialMatch(const SCEV *S, Loop *L,
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SmallVectorImpl<const SCEV *> &Good,
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SmallVectorImpl<const SCEV *> &Bad,
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ScalarEvolution &SE, DominatorTree &DT) {
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// Collect expressions which properly dominate the loop header.
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if (S->properlyDominates(L->getHeader(), &DT)) {
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Good.push_back(S);
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return;
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}
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// Look at add operands.
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if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
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for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
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I != E; ++I)
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DoInitialMatch(*I, L, Good, Bad, SE, DT);
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return;
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}
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// Look at addrec operands.
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if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
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if (!AR->getStart()->isZero()) {
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DoInitialMatch(AR->getStart(), L, Good, Bad, SE, DT);
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DoInitialMatch(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
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AR->getStepRecurrence(SE),
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AR->getLoop()),
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L, Good, Bad, SE, DT);
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return;
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}
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// Handle a multiplication by -1 (negation) if it didn't fold.
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if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S))
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if (Mul->getOperand(0)->isAllOnesValue()) {
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SmallVector<const SCEV *, 4> Ops(Mul->op_begin()+1, Mul->op_end());
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const SCEV *NewMul = SE.getMulExpr(Ops);
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SmallVector<const SCEV *, 4> MyGood;
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SmallVector<const SCEV *, 4> MyBad;
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DoInitialMatch(NewMul, L, MyGood, MyBad, SE, DT);
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const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue(
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SE.getEffectiveSCEVType(NewMul->getType())));
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for (SmallVectorImpl<const SCEV *>::const_iterator I = MyGood.begin(),
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E = MyGood.end(); I != E; ++I)
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Good.push_back(SE.getMulExpr(NegOne, *I));
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for (SmallVectorImpl<const SCEV *>::const_iterator I = MyBad.begin(),
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E = MyBad.end(); I != E; ++I)
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Bad.push_back(SE.getMulExpr(NegOne, *I));
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return;
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}
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// Ok, we can't do anything interesting. Just stuff the whole thing into a
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// register and hope for the best.
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Bad.push_back(S);
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}
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/// InitialMatch - Incorporate loop-variant parts of S into this Formula,
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/// attempting to keep all loop-invariant and loop-computable values in a
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/// single base register.
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void Formula::InitialMatch(const SCEV *S, Loop *L,
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ScalarEvolution &SE, DominatorTree &DT) {
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SmallVector<const SCEV *, 4> Good;
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SmallVector<const SCEV *, 4> Bad;
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DoInitialMatch(S, L, Good, Bad, SE, DT);
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if (!Good.empty()) {
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const SCEV *Sum = SE.getAddExpr(Good);
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if (!Sum->isZero())
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BaseRegs.push_back(Sum);
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AM.HasBaseReg = true;
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}
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if (!Bad.empty()) {
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const SCEV *Sum = SE.getAddExpr(Bad);
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if (!Sum->isZero())
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BaseRegs.push_back(Sum);
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AM.HasBaseReg = true;
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}
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}
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/// getNumRegs - Return the total number of register operands used by this
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/// formula. This does not include register uses implied by non-constant
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/// addrec strides.
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unsigned Formula::getNumRegs() const {
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return !!ScaledReg + BaseRegs.size();
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}
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/// getType - Return the type of this formula, if it has one, or null
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/// otherwise. This type is meaningless except for the bit size.
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const Type *Formula::getType() const {
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return !BaseRegs.empty() ? BaseRegs.front()->getType() :
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ScaledReg ? ScaledReg->getType() :
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AM.BaseGV ? AM.BaseGV->getType() :
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0;
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}
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/// DeleteBaseReg - Delete the given base reg from the BaseRegs list.
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void Formula::DeleteBaseReg(const SCEV *&S) {
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if (&S != &BaseRegs.back())
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std::swap(S, BaseRegs.back());
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BaseRegs.pop_back();
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}
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/// referencesReg - Test if this formula references the given register.
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bool Formula::referencesReg(const SCEV *S) const {
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return S == ScaledReg ||
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std::find(BaseRegs.begin(), BaseRegs.end(), S) != BaseRegs.end();
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}
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/// hasRegsUsedByUsesOtherThan - Test whether this formula uses registers
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/// which are used by uses other than the use with the given index.
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bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx,
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const RegUseTracker &RegUses) const {
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if (ScaledReg)
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if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx))
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return true;
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for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(),
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E = BaseRegs.end(); I != E; ++I)
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if (RegUses.isRegUsedByUsesOtherThan(*I, LUIdx))
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return true;
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return false;
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}
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void Formula::print(raw_ostream &OS) const {
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bool First = true;
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if (AM.BaseGV) {
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if (!First) OS << " + "; else First = false;
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WriteAsOperand(OS, AM.BaseGV, /*PrintType=*/false);
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}
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if (AM.BaseOffs != 0) {
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if (!First) OS << " + "; else First = false;
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OS << AM.BaseOffs;
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}
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for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(),
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E = BaseRegs.end(); I != E; ++I) {
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if (!First) OS << " + "; else First = false;
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OS << "reg(" << **I << ')';
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}
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if (AM.HasBaseReg && BaseRegs.empty()) {
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if (!First) OS << " + "; else First = false;
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OS << "**error: HasBaseReg**";
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} else if (!AM.HasBaseReg && !BaseRegs.empty()) {
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if (!First) OS << " + "; else First = false;
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OS << "**error: !HasBaseReg**";
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}
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if (AM.Scale != 0) {
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if (!First) OS << " + "; else First = false;
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OS << AM.Scale << "*reg(";
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if (ScaledReg)
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OS << *ScaledReg;
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else
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OS << "<unknown>";
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OS << ')';
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}
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}
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void Formula::dump() const {
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print(errs()); errs() << '\n';
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}
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/// isAddRecSExtable - Return true if the given addrec can be sign-extended
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/// without changing its value.
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static bool isAddRecSExtable(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
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const Type *WideTy =
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IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(AR->getType()) + 1);
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return isa<SCEVAddRecExpr>(SE.getSignExtendExpr(AR, WideTy));
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}
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/// isAddSExtable - Return true if the given add can be sign-extended
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/// without changing its value.
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static bool isAddSExtable(const SCEVAddExpr *A, ScalarEvolution &SE) {
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const Type *WideTy =
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IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(A->getType()) + 1);
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return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy));
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}
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/// isMulSExtable - Return true if the given add can be sign-extended
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/// without changing its value.
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static bool isMulSExtable(const SCEVMulExpr *A, ScalarEvolution &SE) {
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const Type *WideTy =
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IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(A->getType()) + 1);
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return isa<SCEVMulExpr>(SE.getSignExtendExpr(A, WideTy));
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}
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/// getExactSDiv - Return an expression for LHS /s RHS, if it can be determined
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/// and if the remainder is known to be zero, or null otherwise. If
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/// IgnoreSignificantBits is true, expressions like (X * Y) /s Y are simplified
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/// to Y, ignoring that the multiplication may overflow, which is useful when
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/// the result will be used in a context where the most significant bits are
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/// ignored.
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static const SCEV *getExactSDiv(const SCEV *LHS, const SCEV *RHS,
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ScalarEvolution &SE,
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bool IgnoreSignificantBits = false) {
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// Handle the trivial case, which works for any SCEV type.
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if (LHS == RHS)
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return SE.getConstant(LHS->getType(), 1);
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// Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do some
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// folding.
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if (RHS->isAllOnesValue())
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return SE.getMulExpr(LHS, RHS);
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// Check for a division of a constant by a constant.
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if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) {
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const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS);
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if (!RC)
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return 0;
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if (C->getValue()->getValue().srem(RC->getValue()->getValue()) != 0)
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return 0;
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return SE.getConstant(C->getValue()->getValue()
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.sdiv(RC->getValue()->getValue()));
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}
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// Distribute the sdiv over addrec operands, if the addrec doesn't overflow.
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if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) {
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if (IgnoreSignificantBits || isAddRecSExtable(AR, SE)) {
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const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE,
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IgnoreSignificantBits);
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if (!Start) return 0;
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const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE,
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IgnoreSignificantBits);
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if (!Step) return 0;
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return SE.getAddRecExpr(Start, Step, AR->getLoop());
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}
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}
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// Distribute the sdiv over add operands, if the add doesn't overflow.
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if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) {
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if (IgnoreSignificantBits || isAddSExtable(Add, SE)) {
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SmallVector<const SCEV *, 8> Ops;
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for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
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I != E; ++I) {
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const SCEV *Op = getExactSDiv(*I, RHS, SE,
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IgnoreSignificantBits);
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if (!Op) return 0;
|
|
Ops.push_back(Op);
|
|
}
|
|
return SE.getAddExpr(Ops);
|
|
}
|
|
}
|
|
|
|
// Check for a multiply operand that we can pull RHS out of.
|
|
if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS))
|
|
if (IgnoreSignificantBits || isMulSExtable(Mul, SE)) {
|
|
SmallVector<const SCEV *, 4> Ops;
|
|
bool Found = false;
|
|
for (SCEVMulExpr::op_iterator I = Mul->op_begin(), E = Mul->op_end();
|
|
I != E; ++I) {
|
|
const SCEV *S = *I;
|
|
if (!Found)
|
|
if (const SCEV *Q = getExactSDiv(S, RHS, SE,
|
|
IgnoreSignificantBits)) {
|
|
S = Q;
|
|
Found = true;
|
|
}
|
|
Ops.push_back(S);
|
|
}
|
|
return Found ? SE.getMulExpr(Ops) : 0;
|
|
}
|
|
|
|
// Otherwise we don't know.
|
|
return 0;
|
|
}
|
|
|
|
/// ExtractImmediate - If S involves the addition of a constant integer value,
|
|
/// return that integer value, and mutate S to point to a new SCEV with that
|
|
/// value excluded.
|
|
static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) {
|
|
if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
|
|
if (C->getValue()->getValue().getMinSignedBits() <= 64) {
|
|
S = SE.getConstant(C->getType(), 0);
|
|
return C->getValue()->getSExtValue();
|
|
}
|
|
} else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
|
|
SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
|
|
int64_t Result = ExtractImmediate(NewOps.front(), SE);
|
|
S = SE.getAddExpr(NewOps);
|
|
return Result;
|
|
} else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
|
|
SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
|
|
int64_t Result = ExtractImmediate(NewOps.front(), SE);
|
|
S = SE.getAddRecExpr(NewOps, AR->getLoop());
|
|
return Result;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/// ExtractSymbol - If S involves the addition of a GlobalValue address,
|
|
/// return that symbol, and mutate S to point to a new SCEV with that
|
|
/// value excluded.
|
|
static GlobalValue *ExtractSymbol(const SCEV *&S, ScalarEvolution &SE) {
|
|
if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
|
|
if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) {
|
|
S = SE.getConstant(GV->getType(), 0);
|
|
return GV;
|
|
}
|
|
} else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
|
|
SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
|
|
GlobalValue *Result = ExtractSymbol(NewOps.back(), SE);
|
|
S = SE.getAddExpr(NewOps);
|
|
return Result;
|
|
} else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
|
|
SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
|
|
GlobalValue *Result = ExtractSymbol(NewOps.front(), SE);
|
|
S = SE.getAddRecExpr(NewOps, AR->getLoop());
|
|
return Result;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/// isAddressUse - Returns true if the specified instruction is using the
|
|
/// specified value as an address.
|
|
static bool isAddressUse(Instruction *Inst, Value *OperandVal) {
|
|
bool isAddress = isa<LoadInst>(Inst);
|
|
if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
|
|
if (SI->getOperand(1) == OperandVal)
|
|
isAddress = true;
|
|
} else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
|
|
// Addressing modes can also be folded into prefetches and a variety
|
|
// of intrinsics.
|
|
switch (II->getIntrinsicID()) {
|
|
default: break;
|
|
case Intrinsic::prefetch:
|
|
case Intrinsic::x86_sse2_loadu_dq:
|
|
case Intrinsic::x86_sse2_loadu_pd:
|
|
case Intrinsic::x86_sse_loadu_ps:
|
|
case Intrinsic::x86_sse_storeu_ps:
|
|
case Intrinsic::x86_sse2_storeu_pd:
|
|
case Intrinsic::x86_sse2_storeu_dq:
|
|
case Intrinsic::x86_sse2_storel_dq:
|
|
if (II->getOperand(1) == OperandVal)
|
|
isAddress = true;
|
|
break;
|
|
}
|
|
}
|
|
return isAddress;
|
|
}
|
|
|
|
/// getAccessType - Return the type of the memory being accessed.
|
|
static const Type *getAccessType(const Instruction *Inst) {
|
|
const Type *AccessTy = Inst->getType();
|
|
if (const StoreInst *SI = dyn_cast<StoreInst>(Inst))
|
|
AccessTy = SI->getOperand(0)->getType();
|
|
else if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
|
|
// Addressing modes can also be folded into prefetches and a variety
|
|
// of intrinsics.
|
|
switch (II->getIntrinsicID()) {
|
|
default: break;
|
|
case Intrinsic::x86_sse_storeu_ps:
|
|
case Intrinsic::x86_sse2_storeu_pd:
|
|
case Intrinsic::x86_sse2_storeu_dq:
|
|
case Intrinsic::x86_sse2_storel_dq:
|
|
AccessTy = II->getOperand(1)->getType();
|
|
break;
|
|
}
|
|
}
|
|
|
|
// All pointers have the same requirements, so canonicalize them to an
|
|
// arbitrary pointer type to minimize variation.
|
|
if (const PointerType *PTy = dyn_cast<PointerType>(AccessTy))
|
|
AccessTy = PointerType::get(IntegerType::get(PTy->getContext(), 1),
|
|
PTy->getAddressSpace());
|
|
|
|
return AccessTy;
|
|
}
|
|
|
|
/// DeleteTriviallyDeadInstructions - If any of the instructions is the
|
|
/// specified set are trivially dead, delete them and see if this makes any of
|
|
/// their operands subsequently dead.
|
|
static bool
|
|
DeleteTriviallyDeadInstructions(SmallVectorImpl<WeakVH> &DeadInsts) {
|
|
bool Changed = false;
|
|
|
|
while (!DeadInsts.empty()) {
|
|
Instruction *I = dyn_cast_or_null<Instruction>(DeadInsts.pop_back_val());
|
|
|
|
if (I == 0 || !isInstructionTriviallyDead(I))
|
|
continue;
|
|
|
|
for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
|
|
if (Instruction *U = dyn_cast<Instruction>(*OI)) {
|
|
*OI = 0;
|
|
if (U->use_empty())
|
|
DeadInsts.push_back(U);
|
|
}
|
|
|
|
I->eraseFromParent();
|
|
Changed = true;
|
|
}
|
|
|
|
return Changed;
|
|
}
|
|
|
|
namespace {
|
|
|
|
/// Cost - This class is used to measure and compare candidate formulae.
|
|
class Cost {
|
|
/// TODO: Some of these could be merged. Also, a lexical ordering
|
|
/// isn't always optimal.
|
|
unsigned NumRegs;
|
|
unsigned AddRecCost;
|
|
unsigned NumIVMuls;
|
|
unsigned NumBaseAdds;
|
|
unsigned ImmCost;
|
|
unsigned SetupCost;
|
|
|
|
public:
|
|
Cost()
|
|
: NumRegs(0), AddRecCost(0), NumIVMuls(0), NumBaseAdds(0), ImmCost(0),
|
|
SetupCost(0) {}
|
|
|
|
unsigned getNumRegs() const { return NumRegs; }
|
|
|
|
bool operator<(const Cost &Other) const;
|
|
|
|
void Loose();
|
|
|
|
void RateFormula(const Formula &F,
|
|
SmallPtrSet<const SCEV *, 16> &Regs,
|
|
const DenseSet<const SCEV *> &VisitedRegs,
|
|
const Loop *L,
|
|
const SmallVectorImpl<int64_t> &Offsets,
|
|
ScalarEvolution &SE, DominatorTree &DT);
|
|
|
|
void print(raw_ostream &OS) const;
|
|
void dump() const;
|
|
|
|
private:
|
|
void RateRegister(const SCEV *Reg,
|
|
SmallPtrSet<const SCEV *, 16> &Regs,
|
|
const Loop *L,
|
|
ScalarEvolution &SE, DominatorTree &DT);
|
|
void RatePrimaryRegister(const SCEV *Reg,
|
|
SmallPtrSet<const SCEV *, 16> &Regs,
|
|
const Loop *L,
|
|
ScalarEvolution &SE, DominatorTree &DT);
|
|
};
|
|
|
|
}
|
|
|
|
/// RateRegister - Tally up interesting quantities from the given register.
|
|
void Cost::RateRegister(const SCEV *Reg,
|
|
SmallPtrSet<const SCEV *, 16> &Regs,
|
|
const Loop *L,
|
|
ScalarEvolution &SE, DominatorTree &DT) {
|
|
if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
|
|
if (AR->getLoop() == L)
|
|
AddRecCost += 1; /// TODO: This should be a function of the stride.
|
|
|
|
// If this is an addrec for a loop that's already been visited by LSR,
|
|
// don't second-guess its addrec phi nodes. LSR isn't currently smart
|
|
// enough to reason about more than one loop at a time. Consider these
|
|
// registers free and leave them alone.
|
|
else if (L->contains(AR->getLoop()) ||
|
|
(!AR->getLoop()->contains(L) &&
|
|
DT.dominates(L->getHeader(), AR->getLoop()->getHeader()))) {
|
|
for (BasicBlock::iterator I = AR->getLoop()->getHeader()->begin();
|
|
PHINode *PN = dyn_cast<PHINode>(I); ++I)
|
|
if (SE.isSCEVable(PN->getType()) &&
|
|
(SE.getEffectiveSCEVType(PN->getType()) ==
|
|
SE.getEffectiveSCEVType(AR->getType())) &&
|
|
SE.getSCEV(PN) == AR)
|
|
return;
|
|
|
|
// If this isn't one of the addrecs that the loop already has, it
|
|
// would require a costly new phi and add. TODO: This isn't
|
|
// precisely modeled right now.
|
|
++NumBaseAdds;
|
|
if (!Regs.count(AR->getStart()))
|
|
RateRegister(AR->getStart(), Regs, L, SE, DT);
|
|
}
|
|
|
|
// Add the step value register, if it needs one.
|
|
// TODO: The non-affine case isn't precisely modeled here.
|
|
if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1)))
|
|
if (!Regs.count(AR->getStart()))
|
|
RateRegister(AR->getOperand(1), Regs, L, SE, DT);
|
|
}
|
|
++NumRegs;
|
|
|
|
// Rough heuristic; favor registers which don't require extra setup
|
|
// instructions in the preheader.
|
|
if (!isa<SCEVUnknown>(Reg) &&
|
|
!isa<SCEVConstant>(Reg) &&
|
|
!(isa<SCEVAddRecExpr>(Reg) &&
|
|
(isa<SCEVUnknown>(cast<SCEVAddRecExpr>(Reg)->getStart()) ||
|
|
isa<SCEVConstant>(cast<SCEVAddRecExpr>(Reg)->getStart()))))
|
|
++SetupCost;
|
|
}
|
|
|
|
/// RatePrimaryRegister - Record this register in the set. If we haven't seen it
|
|
/// before, rate it.
|
|
void Cost::RatePrimaryRegister(const SCEV *Reg,
|
|
SmallPtrSet<const SCEV *, 16> &Regs,
|
|
const Loop *L,
|
|
ScalarEvolution &SE, DominatorTree &DT) {
|
|
if (Regs.insert(Reg))
|
|
RateRegister(Reg, Regs, L, SE, DT);
|
|
}
|
|
|
|
void Cost::RateFormula(const Formula &F,
|
|
SmallPtrSet<const SCEV *, 16> &Regs,
|
|
const DenseSet<const SCEV *> &VisitedRegs,
|
|
const Loop *L,
|
|
const SmallVectorImpl<int64_t> &Offsets,
|
|
ScalarEvolution &SE, DominatorTree &DT) {
|
|
// Tally up the registers.
|
|
if (const SCEV *ScaledReg = F.ScaledReg) {
|
|
if (VisitedRegs.count(ScaledReg)) {
|
|
Loose();
|
|
return;
|
|
}
|
|
RatePrimaryRegister(ScaledReg, Regs, L, SE, DT);
|
|
}
|
|
for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
|
|
E = F.BaseRegs.end(); I != E; ++I) {
|
|
const SCEV *BaseReg = *I;
|
|
if (VisitedRegs.count(BaseReg)) {
|
|
Loose();
|
|
return;
|
|
}
|
|
RatePrimaryRegister(BaseReg, Regs, L, SE, DT);
|
|
|
|
NumIVMuls += isa<SCEVMulExpr>(BaseReg) &&
|
|
BaseReg->hasComputableLoopEvolution(L);
|
|
}
|
|
|
|
if (F.BaseRegs.size() > 1)
|
|
NumBaseAdds += F.BaseRegs.size() - 1;
|
|
|
|
// Tally up the non-zero immediates.
|
|
for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(),
|
|
E = Offsets.end(); I != E; ++I) {
|
|
int64_t Offset = (uint64_t)*I + F.AM.BaseOffs;
|
|
if (F.AM.BaseGV)
|
|
ImmCost += 64; // Handle symbolic values conservatively.
|
|
// TODO: This should probably be the pointer size.
|
|
else if (Offset != 0)
|
|
ImmCost += APInt(64, Offset, true).getMinSignedBits();
|
|
}
|
|
}
|
|
|
|
/// Loose - Set this cost to a loosing value.
|
|
void Cost::Loose() {
|
|
NumRegs = ~0u;
|
|
AddRecCost = ~0u;
|
|
NumIVMuls = ~0u;
|
|
NumBaseAdds = ~0u;
|
|
ImmCost = ~0u;
|
|
SetupCost = ~0u;
|
|
}
|
|
|
|
/// operator< - Choose the lower cost.
|
|
bool Cost::operator<(const Cost &Other) const {
|
|
if (NumRegs != Other.NumRegs)
|
|
return NumRegs < Other.NumRegs;
|
|
if (AddRecCost != Other.AddRecCost)
|
|
return AddRecCost < Other.AddRecCost;
|
|
if (NumIVMuls != Other.NumIVMuls)
|
|
return NumIVMuls < Other.NumIVMuls;
|
|
if (NumBaseAdds != Other.NumBaseAdds)
|
|
return NumBaseAdds < Other.NumBaseAdds;
|
|
if (ImmCost != Other.ImmCost)
|
|
return ImmCost < Other.ImmCost;
|
|
if (SetupCost != Other.SetupCost)
|
|
return SetupCost < Other.SetupCost;
|
|
return false;
|
|
}
|
|
|
|
void Cost::print(raw_ostream &OS) const {
|
|
OS << NumRegs << " reg" << (NumRegs == 1 ? "" : "s");
|
|
if (AddRecCost != 0)
|
|
OS << ", with addrec cost " << AddRecCost;
|
|
if (NumIVMuls != 0)
|
|
OS << ", plus " << NumIVMuls << " IV mul" << (NumIVMuls == 1 ? "" : "s");
|
|
if (NumBaseAdds != 0)
|
|
OS << ", plus " << NumBaseAdds << " base add"
|
|
<< (NumBaseAdds == 1 ? "" : "s");
|
|
if (ImmCost != 0)
|
|
OS << ", plus " << ImmCost << " imm cost";
|
|
if (SetupCost != 0)
|
|
OS << ", plus " << SetupCost << " setup cost";
|
|
}
|
|
|
|
void Cost::dump() const {
|
|
print(errs()); errs() << '\n';
|
|
}
|
|
|
|
namespace {
|
|
|
|
/// LSRFixup - An operand value in an instruction which is to be replaced
|
|
/// with some equivalent, possibly strength-reduced, replacement.
|
|
struct LSRFixup {
|
|
/// UserInst - The instruction which will be updated.
|
|
Instruction *UserInst;
|
|
|
|
/// OperandValToReplace - The operand of the instruction which will
|
|
/// be replaced. The operand may be used more than once; every instance
|
|
/// will be replaced.
|
|
Value *OperandValToReplace;
|
|
|
|
/// PostIncLoops - If this user is to use the post-incremented value of an
|
|
/// induction variable, this variable is non-null and holds the loop
|
|
/// associated with the induction variable.
|
|
PostIncLoopSet PostIncLoops;
|
|
|
|
/// LUIdx - The index of the LSRUse describing the expression which
|
|
/// this fixup needs, minus an offset (below).
|
|
size_t LUIdx;
|
|
|
|
/// Offset - A constant offset to be added to the LSRUse expression.
|
|
/// This allows multiple fixups to share the same LSRUse with different
|
|
/// offsets, for example in an unrolled loop.
|
|
int64_t Offset;
|
|
|
|
bool isUseFullyOutsideLoop(const Loop *L) const;
|
|
|
|
LSRFixup();
|
|
|
|
void print(raw_ostream &OS) const;
|
|
void dump() const;
|
|
};
|
|
|
|
}
|
|
|
|
LSRFixup::LSRFixup()
|
|
: UserInst(0), OperandValToReplace(0), LUIdx(~size_t(0)), Offset(0) {}
|
|
|
|
/// isUseFullyOutsideLoop - Test whether this fixup always uses its
|
|
/// value outside of the given loop.
|
|
bool LSRFixup::isUseFullyOutsideLoop(const Loop *L) const {
|
|
// PHI nodes use their value in their incoming blocks.
|
|
if (const PHINode *PN = dyn_cast<PHINode>(UserInst)) {
|
|
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
|
|
if (PN->getIncomingValue(i) == OperandValToReplace &&
|
|
L->contains(PN->getIncomingBlock(i)))
|
|
return false;
|
|
return true;
|
|
}
|
|
|
|
return !L->contains(UserInst);
|
|
}
|
|
|
|
void LSRFixup::print(raw_ostream &OS) const {
|
|
OS << "UserInst=";
|
|
// Store is common and interesting enough to be worth special-casing.
|
|
if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) {
|
|
OS << "store ";
|
|
WriteAsOperand(OS, Store->getOperand(0), /*PrintType=*/false);
|
|
} else if (UserInst->getType()->isVoidTy())
|
|
OS << UserInst->getOpcodeName();
|
|
else
|
|
WriteAsOperand(OS, UserInst, /*PrintType=*/false);
|
|
|
|
OS << ", OperandValToReplace=";
|
|
WriteAsOperand(OS, OperandValToReplace, /*PrintType=*/false);
|
|
|
|
for (PostIncLoopSet::const_iterator I = PostIncLoops.begin(),
|
|
E = PostIncLoops.end(); I != E; ++I) {
|
|
OS << ", PostIncLoop=";
|
|
WriteAsOperand(OS, (*I)->getHeader(), /*PrintType=*/false);
|
|
}
|
|
|
|
if (LUIdx != ~size_t(0))
|
|
OS << ", LUIdx=" << LUIdx;
|
|
|
|
if (Offset != 0)
|
|
OS << ", Offset=" << Offset;
|
|
}
|
|
|
|
void LSRFixup::dump() const {
|
|
print(errs()); errs() << '\n';
|
|
}
|
|
|
|
namespace {
|
|
|
|
/// UniquifierDenseMapInfo - A DenseMapInfo implementation for holding
|
|
/// DenseMaps and DenseSets of sorted SmallVectors of const SCEV*.
|
|
struct UniquifierDenseMapInfo {
|
|
static SmallVector<const SCEV *, 2> getEmptyKey() {
|
|
SmallVector<const SCEV *, 2> V;
|
|
V.push_back(reinterpret_cast<const SCEV *>(-1));
|
|
return V;
|
|
}
|
|
|
|
static SmallVector<const SCEV *, 2> getTombstoneKey() {
|
|
SmallVector<const SCEV *, 2> V;
|
|
V.push_back(reinterpret_cast<const SCEV *>(-2));
|
|
return V;
|
|
}
|
|
|
|
static unsigned getHashValue(const SmallVector<const SCEV *, 2> &V) {
|
|
unsigned Result = 0;
|
|
for (SmallVectorImpl<const SCEV *>::const_iterator I = V.begin(),
|
|
E = V.end(); I != E; ++I)
|
|
Result ^= DenseMapInfo<const SCEV *>::getHashValue(*I);
|
|
return Result;
|
|
}
|
|
|
|
static bool isEqual(const SmallVector<const SCEV *, 2> &LHS,
|
|
const SmallVector<const SCEV *, 2> &RHS) {
|
|
return LHS == RHS;
|
|
}
|
|
};
|
|
|
|
/// LSRUse - This class holds the state that LSR keeps for each use in
|
|
/// IVUsers, as well as uses invented by LSR itself. It includes information
|
|
/// about what kinds of things can be folded into the user, information about
|
|
/// the user itself, and information about how the use may be satisfied.
|
|
/// TODO: Represent multiple users of the same expression in common?
|
|
class LSRUse {
|
|
DenseSet<SmallVector<const SCEV *, 2>, UniquifierDenseMapInfo> Uniquifier;
|
|
|
|
public:
|
|
/// KindType - An enum for a kind of use, indicating what types of
|
|
/// scaled and immediate operands it might support.
|
|
enum KindType {
|
|
Basic, ///< A normal use, with no folding.
|
|
Special, ///< A special case of basic, allowing -1 scales.
|
|
Address, ///< An address use; folding according to TargetLowering
|
|
ICmpZero ///< An equality icmp with both operands folded into one.
|
|
// TODO: Add a generic icmp too?
|
|
};
|
|
|
|
KindType Kind;
|
|
const Type *AccessTy;
|
|
|
|
SmallVector<int64_t, 8> Offsets;
|
|
int64_t MinOffset;
|
|
int64_t MaxOffset;
|
|
|
|
/// AllFixupsOutsideLoop - This records whether all of the fixups using this
|
|
/// LSRUse are outside of the loop, in which case some special-case heuristics
|
|
/// may be used.
|
|
bool AllFixupsOutsideLoop;
|
|
|
|
/// Formulae - A list of ways to build a value that can satisfy this user.
|
|
/// After the list is populated, one of these is selected heuristically and
|
|
/// used to formulate a replacement for OperandValToReplace in UserInst.
|
|
SmallVector<Formula, 12> Formulae;
|
|
|
|
/// Regs - The set of register candidates used by all formulae in this LSRUse.
|
|
SmallPtrSet<const SCEV *, 4> Regs;
|
|
|
|
LSRUse(KindType K, const Type *T) : Kind(K), AccessTy(T),
|
|
MinOffset(INT64_MAX),
|
|
MaxOffset(INT64_MIN),
|
|
AllFixupsOutsideLoop(true) {}
|
|
|
|
bool HasFormulaWithSameRegs(const Formula &F) const;
|
|
bool InsertFormula(const Formula &F);
|
|
void DeleteFormula(Formula &F);
|
|
void RecomputeRegs(size_t LUIdx, RegUseTracker &Reguses);
|
|
|
|
void check() const;
|
|
|
|
void print(raw_ostream &OS) const;
|
|
void dump() const;
|
|
};
|
|
|
|
/// HasFormula - Test whether this use as a formula which has the same
|
|
/// registers as the given formula.
|
|
bool LSRUse::HasFormulaWithSameRegs(const Formula &F) const {
|
|
SmallVector<const SCEV *, 2> Key = F.BaseRegs;
|
|
if (F.ScaledReg) Key.push_back(F.ScaledReg);
|
|
// Unstable sort by host order ok, because this is only used for uniquifying.
|
|
std::sort(Key.begin(), Key.end());
|
|
return Uniquifier.count(Key);
|
|
}
|
|
|
|
/// InsertFormula - If the given formula has not yet been inserted, add it to
|
|
/// the list, and return true. Return false otherwise.
|
|
bool LSRUse::InsertFormula(const Formula &F) {
|
|
SmallVector<const SCEV *, 2> Key = F.BaseRegs;
|
|
if (F.ScaledReg) Key.push_back(F.ScaledReg);
|
|
// Unstable sort by host order ok, because this is only used for uniquifying.
|
|
std::sort(Key.begin(), Key.end());
|
|
|
|
if (!Uniquifier.insert(Key).second)
|
|
return false;
|
|
|
|
// Using a register to hold the value of 0 is not profitable.
|
|
assert((!F.ScaledReg || !F.ScaledReg->isZero()) &&
|
|
"Zero allocated in a scaled register!");
|
|
#ifndef NDEBUG
|
|
for (SmallVectorImpl<const SCEV *>::const_iterator I =
|
|
F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I)
|
|
assert(!(*I)->isZero() && "Zero allocated in a base register!");
|
|
#endif
|
|
|
|
// Add the formula to the list.
|
|
Formulae.push_back(F);
|
|
|
|
// Record registers now being used by this use.
|
|
if (F.ScaledReg) Regs.insert(F.ScaledReg);
|
|
Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
|
|
|
|
return true;
|
|
}
|
|
|
|
/// DeleteFormula - Remove the given formula from this use's list.
|
|
void LSRUse::DeleteFormula(Formula &F) {
|
|
if (&F != &Formulae.back())
|
|
std::swap(F, Formulae.back());
|
|
Formulae.pop_back();
|
|
assert(!Formulae.empty() && "LSRUse has no formulae left!");
|
|
}
|
|
|
|
/// RecomputeRegs - Recompute the Regs field, and update RegUses.
|
|
void LSRUse::RecomputeRegs(size_t LUIdx, RegUseTracker &RegUses) {
|
|
// Now that we've filtered out some formulae, recompute the Regs set.
|
|
SmallPtrSet<const SCEV *, 4> OldRegs = Regs;
|
|
Regs.clear();
|
|
for (SmallVectorImpl<Formula>::const_iterator I = Formulae.begin(),
|
|
E = Formulae.end(); I != E; ++I) {
|
|
const Formula &F = *I;
|
|
if (F.ScaledReg) Regs.insert(F.ScaledReg);
|
|
Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
|
|
}
|
|
|
|
// Update the RegTracker.
|
|
for (SmallPtrSet<const SCEV *, 4>::iterator I = OldRegs.begin(),
|
|
E = OldRegs.end(); I != E; ++I)
|
|
if (!Regs.count(*I))
|
|
RegUses.DropRegister(*I, LUIdx);
|
|
}
|
|
|
|
void LSRUse::print(raw_ostream &OS) const {
|
|
OS << "LSR Use: Kind=";
|
|
switch (Kind) {
|
|
case Basic: OS << "Basic"; break;
|
|
case Special: OS << "Special"; break;
|
|
case ICmpZero: OS << "ICmpZero"; break;
|
|
case Address:
|
|
OS << "Address of ";
|
|
if (AccessTy->isPointerTy())
|
|
OS << "pointer"; // the full pointer type could be really verbose
|
|
else
|
|
OS << *AccessTy;
|
|
}
|
|
|
|
OS << ", Offsets={";
|
|
for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(),
|
|
E = Offsets.end(); I != E; ++I) {
|
|
OS << *I;
|
|
if (next(I) != E)
|
|
OS << ',';
|
|
}
|
|
OS << '}';
|
|
|
|
if (AllFixupsOutsideLoop)
|
|
OS << ", all-fixups-outside-loop";
|
|
}
|
|
|
|
void LSRUse::dump() const {
|
|
print(errs()); errs() << '\n';
|
|
}
|
|
|
|
/// isLegalUse - Test whether the use described by AM is "legal", meaning it can
|
|
/// be completely folded into the user instruction at isel time. This includes
|
|
/// address-mode folding and special icmp tricks.
|
|
static bool isLegalUse(const TargetLowering::AddrMode &AM,
|
|
LSRUse::KindType Kind, const Type *AccessTy,
|
|
const TargetLowering *TLI) {
|
|
switch (Kind) {
|
|
case LSRUse::Address:
|
|
// If we have low-level target information, ask the target if it can
|
|
// completely fold this address.
|
|
if (TLI) return TLI->isLegalAddressingMode(AM, AccessTy);
|
|
|
|
// Otherwise, just guess that reg+reg addressing is legal.
|
|
return !AM.BaseGV && AM.BaseOffs == 0 && AM.Scale <= 1;
|
|
|
|
case LSRUse::ICmpZero:
|
|
// There's not even a target hook for querying whether it would be legal to
|
|
// fold a GV into an ICmp.
|
|
if (AM.BaseGV)
|
|
return false;
|
|
|
|
// ICmp only has two operands; don't allow more than two non-trivial parts.
|
|
if (AM.Scale != 0 && AM.HasBaseReg && AM.BaseOffs != 0)
|
|
return false;
|
|
|
|
// ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by
|
|
// putting the scaled register in the other operand of the icmp.
|
|
if (AM.Scale != 0 && AM.Scale != -1)
|
|
return false;
|
|
|
|
// If we have low-level target information, ask the target if it can fold an
|
|
// integer immediate on an icmp.
|
|
if (AM.BaseOffs != 0) {
|
|
if (TLI) return TLI->isLegalICmpImmediate(-AM.BaseOffs);
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
|
|
case LSRUse::Basic:
|
|
// Only handle single-register values.
|
|
return !AM.BaseGV && AM.Scale == 0 && AM.BaseOffs == 0;
|
|
|
|
case LSRUse::Special:
|
|
// Only handle -1 scales, or no scale.
|
|
return AM.Scale == 0 || AM.Scale == -1;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
static bool isLegalUse(TargetLowering::AddrMode AM,
|
|
int64_t MinOffset, int64_t MaxOffset,
|
|
LSRUse::KindType Kind, const Type *AccessTy,
|
|
const TargetLowering *TLI) {
|
|
// Check for overflow.
|
|
if (((int64_t)((uint64_t)AM.BaseOffs + MinOffset) > AM.BaseOffs) !=
|
|
(MinOffset > 0))
|
|
return false;
|
|
AM.BaseOffs = (uint64_t)AM.BaseOffs + MinOffset;
|
|
if (isLegalUse(AM, Kind, AccessTy, TLI)) {
|
|
AM.BaseOffs = (uint64_t)AM.BaseOffs - MinOffset;
|
|
// Check for overflow.
|
|
if (((int64_t)((uint64_t)AM.BaseOffs + MaxOffset) > AM.BaseOffs) !=
|
|
(MaxOffset > 0))
|
|
return false;
|
|
AM.BaseOffs = (uint64_t)AM.BaseOffs + MaxOffset;
|
|
return isLegalUse(AM, Kind, AccessTy, TLI);
|
|
}
|
|
return false;
|
|
}
|
|
|
|
static bool isAlwaysFoldable(int64_t BaseOffs,
|
|
GlobalValue *BaseGV,
|
|
bool HasBaseReg,
|
|
LSRUse::KindType Kind, const Type *AccessTy,
|
|
const TargetLowering *TLI) {
|
|
// Fast-path: zero is always foldable.
|
|
if (BaseOffs == 0 && !BaseGV) return true;
|
|
|
|
// Conservatively, create an address with an immediate and a
|
|
// base and a scale.
|
|
TargetLowering::AddrMode AM;
|
|
AM.BaseOffs = BaseOffs;
|
|
AM.BaseGV = BaseGV;
|
|
AM.HasBaseReg = HasBaseReg;
|
|
AM.Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
|
|
|
|
// Canonicalize a scale of 1 to a base register if the formula doesn't
|
|
// already have a base register.
|
|
if (!AM.HasBaseReg && AM.Scale == 1) {
|
|
AM.Scale = 0;
|
|
AM.HasBaseReg = true;
|
|
}
|
|
|
|
return isLegalUse(AM, Kind, AccessTy, TLI);
|
|
}
|
|
|
|
static bool isAlwaysFoldable(const SCEV *S,
|
|
int64_t MinOffset, int64_t MaxOffset,
|
|
bool HasBaseReg,
|
|
LSRUse::KindType Kind, const Type *AccessTy,
|
|
const TargetLowering *TLI,
|
|
ScalarEvolution &SE) {
|
|
// Fast-path: zero is always foldable.
|
|
if (S->isZero()) return true;
|
|
|
|
// Conservatively, create an address with an immediate and a
|
|
// base and a scale.
|
|
int64_t BaseOffs = ExtractImmediate(S, SE);
|
|
GlobalValue *BaseGV = ExtractSymbol(S, SE);
|
|
|
|
// If there's anything else involved, it's not foldable.
|
|
if (!S->isZero()) return false;
|
|
|
|
// Fast-path: zero is always foldable.
|
|
if (BaseOffs == 0 && !BaseGV) return true;
|
|
|
|
// Conservatively, create an address with an immediate and a
|
|
// base and a scale.
|
|
TargetLowering::AddrMode AM;
|
|
AM.BaseOffs = BaseOffs;
|
|
AM.BaseGV = BaseGV;
|
|
AM.HasBaseReg = HasBaseReg;
|
|
AM.Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
|
|
|
|
return isLegalUse(AM, MinOffset, MaxOffset, Kind, AccessTy, TLI);
|
|
}
|
|
|
|
/// FormulaSorter - This class implements an ordering for formulae which sorts
|
|
/// the by their standalone cost.
|
|
class FormulaSorter {
|
|
/// These two sets are kept empty, so that we compute standalone costs.
|
|
DenseSet<const SCEV *> VisitedRegs;
|
|
SmallPtrSet<const SCEV *, 16> Regs;
|
|
Loop *L;
|
|
LSRUse *LU;
|
|
ScalarEvolution &SE;
|
|
DominatorTree &DT;
|
|
|
|
public:
|
|
FormulaSorter(Loop *l, LSRUse &lu, ScalarEvolution &se, DominatorTree &dt)
|
|
: L(l), LU(&lu), SE(se), DT(dt) {}
|
|
|
|
bool operator()(const Formula &A, const Formula &B) {
|
|
Cost CostA;
|
|
CostA.RateFormula(A, Regs, VisitedRegs, L, LU->Offsets, SE, DT);
|
|
Regs.clear();
|
|
Cost CostB;
|
|
CostB.RateFormula(B, Regs, VisitedRegs, L, LU->Offsets, SE, DT);
|
|
Regs.clear();
|
|
return CostA < CostB;
|
|
}
|
|
};
|
|
|
|
/// LSRInstance - This class holds state for the main loop strength reduction
|
|
/// logic.
|
|
class LSRInstance {
|
|
IVUsers &IU;
|
|
ScalarEvolution &SE;
|
|
DominatorTree &DT;
|
|
LoopInfo &LI;
|
|
const TargetLowering *const TLI;
|
|
Loop *const L;
|
|
bool Changed;
|
|
|
|
/// IVIncInsertPos - This is the insert position that the current loop's
|
|
/// induction variable increment should be placed. In simple loops, this is
|
|
/// the latch block's terminator. But in more complicated cases, this is a
|
|
/// position which will dominate all the in-loop post-increment users.
|
|
Instruction *IVIncInsertPos;
|
|
|
|
/// Factors - Interesting factors between use strides.
|
|
SmallSetVector<int64_t, 8> Factors;
|
|
|
|
/// Types - Interesting use types, to facilitate truncation reuse.
|
|
SmallSetVector<const Type *, 4> Types;
|
|
|
|
/// Fixups - The list of operands which are to be replaced.
|
|
SmallVector<LSRFixup, 16> Fixups;
|
|
|
|
/// Uses - The list of interesting uses.
|
|
SmallVector<LSRUse, 16> Uses;
|
|
|
|
/// RegUses - Track which uses use which register candidates.
|
|
RegUseTracker RegUses;
|
|
|
|
void OptimizeShadowIV();
|
|
bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse);
|
|
ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse);
|
|
void OptimizeLoopTermCond();
|
|
|
|
void CollectInterestingTypesAndFactors();
|
|
void CollectFixupsAndInitialFormulae();
|
|
|
|
LSRFixup &getNewFixup() {
|
|
Fixups.push_back(LSRFixup());
|
|
return Fixups.back();
|
|
}
|
|
|
|
// Support for sharing of LSRUses between LSRFixups.
|
|
typedef DenseMap<const SCEV *, size_t> UseMapTy;
|
|
UseMapTy UseMap;
|
|
|
|
bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
|
|
LSRUse::KindType Kind, const Type *AccessTy);
|
|
|
|
std::pair<size_t, int64_t> getUse(const SCEV *&Expr,
|
|
LSRUse::KindType Kind,
|
|
const Type *AccessTy);
|
|
|
|
void DeleteUse(LSRUse &LU);
|
|
|
|
LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU);
|
|
|
|
public:
|
|
void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
|
|
void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
|
|
void CountRegisters(const Formula &F, size_t LUIdx);
|
|
bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F);
|
|
|
|
void CollectLoopInvariantFixupsAndFormulae();
|
|
|
|
void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base,
|
|
unsigned Depth = 0);
|
|
void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base);
|
|
void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
|
|
void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
|
|
void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base);
|
|
void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base);
|
|
void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base);
|
|
void GenerateCrossUseConstantOffsets();
|
|
void GenerateAllReuseFormulae();
|
|
|
|
void FilterOutUndesirableDedicatedRegisters();
|
|
|
|
size_t EstimateSearchSpaceComplexity() const;
|
|
void NarrowSearchSpaceUsingHeuristics();
|
|
|
|
void SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
|
|
Cost &SolutionCost,
|
|
SmallVectorImpl<const Formula *> &Workspace,
|
|
const Cost &CurCost,
|
|
const SmallPtrSet<const SCEV *, 16> &CurRegs,
|
|
DenseSet<const SCEV *> &VisitedRegs) const;
|
|
void Solve(SmallVectorImpl<const Formula *> &Solution) const;
|
|
|
|
BasicBlock::iterator
|
|
HoistInsertPosition(BasicBlock::iterator IP,
|
|
const SmallVectorImpl<Instruction *> &Inputs) const;
|
|
BasicBlock::iterator AdjustInsertPositionForExpand(BasicBlock::iterator IP,
|
|
const LSRFixup &LF,
|
|
const LSRUse &LU) const;
|
|
|
|
Value *Expand(const LSRFixup &LF,
|
|
const Formula &F,
|
|
BasicBlock::iterator IP,
|
|
SCEVExpander &Rewriter,
|
|
SmallVectorImpl<WeakVH> &DeadInsts) const;
|
|
void RewriteForPHI(PHINode *PN, const LSRFixup &LF,
|
|
const Formula &F,
|
|
SCEVExpander &Rewriter,
|
|
SmallVectorImpl<WeakVH> &DeadInsts,
|
|
Pass *P) const;
|
|
void Rewrite(const LSRFixup &LF,
|
|
const Formula &F,
|
|
SCEVExpander &Rewriter,
|
|
SmallVectorImpl<WeakVH> &DeadInsts,
|
|
Pass *P) const;
|
|
void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution,
|
|
Pass *P);
|
|
|
|
LSRInstance(const TargetLowering *tli, Loop *l, Pass *P);
|
|
|
|
bool getChanged() const { return Changed; }
|
|
|
|
void print_factors_and_types(raw_ostream &OS) const;
|
|
void print_fixups(raw_ostream &OS) const;
|
|
void print_uses(raw_ostream &OS) const;
|
|
void print(raw_ostream &OS) const;
|
|
void dump() const;
|
|
};
|
|
|
|
}
|
|
|
|
/// OptimizeShadowIV - If IV is used in a int-to-float cast
|
|
/// inside the loop then try to eliminate the cast operation.
|
|
void LSRInstance::OptimizeShadowIV() {
|
|
const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
|
|
if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
|
|
return;
|
|
|
|
for (IVUsers::const_iterator UI = IU.begin(), E = IU.end();
|
|
UI != E; /* empty */) {
|
|
IVUsers::const_iterator CandidateUI = UI;
|
|
++UI;
|
|
Instruction *ShadowUse = CandidateUI->getUser();
|
|
const Type *DestTy = NULL;
|
|
|
|
/* If shadow use is a int->float cast then insert a second IV
|
|
to eliminate this cast.
|
|
|
|
for (unsigned i = 0; i < n; ++i)
|
|
foo((double)i);
|
|
|
|
is transformed into
|
|
|
|
double d = 0.0;
|
|
for (unsigned i = 0; i < n; ++i, ++d)
|
|
foo(d);
|
|
*/
|
|
if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser()))
|
|
DestTy = UCast->getDestTy();
|
|
else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser()))
|
|
DestTy = SCast->getDestTy();
|
|
if (!DestTy) continue;
|
|
|
|
if (TLI) {
|
|
// If target does not support DestTy natively then do not apply
|
|
// this transformation.
|
|
EVT DVT = TLI->getValueType(DestTy);
|
|
if (!TLI->isTypeLegal(DVT)) continue;
|
|
}
|
|
|
|
PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
|
|
if (!PH) continue;
|
|
if (PH->getNumIncomingValues() != 2) continue;
|
|
|
|
const Type *SrcTy = PH->getType();
|
|
int Mantissa = DestTy->getFPMantissaWidth();
|
|
if (Mantissa == -1) continue;
|
|
if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa)
|
|
continue;
|
|
|
|
unsigned Entry, Latch;
|
|
if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
|
|
Entry = 0;
|
|
Latch = 1;
|
|
} else {
|
|
Entry = 1;
|
|
Latch = 0;
|
|
}
|
|
|
|
ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
|
|
if (!Init) continue;
|
|
Constant *NewInit = ConstantFP::get(DestTy, Init->getZExtValue());
|
|
|
|
BinaryOperator *Incr =
|
|
dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
|
|
if (!Incr) continue;
|
|
if (Incr->getOpcode() != Instruction::Add
|
|
&& Incr->getOpcode() != Instruction::Sub)
|
|
continue;
|
|
|
|
/* Initialize new IV, double d = 0.0 in above example. */
|
|
ConstantInt *C = NULL;
|
|
if (Incr->getOperand(0) == PH)
|
|
C = dyn_cast<ConstantInt>(Incr->getOperand(1));
|
|
else if (Incr->getOperand(1) == PH)
|
|
C = dyn_cast<ConstantInt>(Incr->getOperand(0));
|
|
else
|
|
continue;
|
|
|
|
if (!C) continue;
|
|
|
|
// Ignore negative constants, as the code below doesn't handle them
|
|
// correctly. TODO: Remove this restriction.
|
|
if (!C->getValue().isStrictlyPositive()) continue;
|
|
|
|
/* Add new PHINode. */
|
|
PHINode *NewPH = PHINode::Create(DestTy, "IV.S.", PH);
|
|
|
|
/* create new increment. '++d' in above example. */
|
|
Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
|
|
BinaryOperator *NewIncr =
|
|
BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
|
|
Instruction::FAdd : Instruction::FSub,
|
|
NewPH, CFP, "IV.S.next.", Incr);
|
|
|
|
NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
|
|
NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
|
|
|
|
/* Remove cast operation */
|
|
ShadowUse->replaceAllUsesWith(NewPH);
|
|
ShadowUse->eraseFromParent();
|
|
Changed = true;
|
|
break;
|
|
}
|
|
}
|
|
|
|
/// FindIVUserForCond - If Cond has an operand that is an expression of an IV,
|
|
/// set the IV user and stride information and return true, otherwise return
|
|
/// false.
|
|
bool LSRInstance::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse) {
|
|
for (IVUsers::iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
|
|
if (UI->getUser() == Cond) {
|
|
// NOTE: we could handle setcc instructions with multiple uses here, but
|
|
// InstCombine does it as well for simple uses, it's not clear that it
|
|
// occurs enough in real life to handle.
|
|
CondUse = UI;
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// OptimizeMax - Rewrite the loop's terminating condition if it uses
|
|
/// a max computation.
|
|
///
|
|
/// This is a narrow solution to a specific, but acute, problem. For loops
|
|
/// like this:
|
|
///
|
|
/// i = 0;
|
|
/// do {
|
|
/// p[i] = 0.0;
|
|
/// } while (++i < n);
|
|
///
|
|
/// the trip count isn't just 'n', because 'n' might not be positive. And
|
|
/// unfortunately this can come up even for loops where the user didn't use
|
|
/// a C do-while loop. For example, seemingly well-behaved top-test loops
|
|
/// will commonly be lowered like this:
|
|
//
|
|
/// if (n > 0) {
|
|
/// i = 0;
|
|
/// do {
|
|
/// p[i] = 0.0;
|
|
/// } while (++i < n);
|
|
/// }
|
|
///
|
|
/// and then it's possible for subsequent optimization to obscure the if
|
|
/// test in such a way that indvars can't find it.
|
|
///
|
|
/// When indvars can't find the if test in loops like this, it creates a
|
|
/// max expression, which allows it to give the loop a canonical
|
|
/// induction variable:
|
|
///
|
|
/// i = 0;
|
|
/// max = n < 1 ? 1 : n;
|
|
/// do {
|
|
/// p[i] = 0.0;
|
|
/// } while (++i != max);
|
|
///
|
|
/// Canonical induction variables are necessary because the loop passes
|
|
/// are designed around them. The most obvious example of this is the
|
|
/// LoopInfo analysis, which doesn't remember trip count values. It
|
|
/// expects to be able to rediscover the trip count each time it is
|
|
/// needed, and it does this using a simple analysis that only succeeds if
|
|
/// the loop has a canonical induction variable.
|
|
///
|
|
/// However, when it comes time to generate code, the maximum operation
|
|
/// can be quite costly, especially if it's inside of an outer loop.
|
|
///
|
|
/// This function solves this problem by detecting this type of loop and
|
|
/// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
|
|
/// the instructions for the maximum computation.
|
|
///
|
|
ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
|
|
// Check that the loop matches the pattern we're looking for.
|
|
if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
|
|
Cond->getPredicate() != CmpInst::ICMP_NE)
|
|
return Cond;
|
|
|
|
SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
|
|
if (!Sel || !Sel->hasOneUse()) return Cond;
|
|
|
|
const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
|
|
if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
|
|
return Cond;
|
|
const SCEV *One = SE.getConstant(BackedgeTakenCount->getType(), 1);
|
|
|
|
// Add one to the backedge-taken count to get the trip count.
|
|
const SCEV *IterationCount = SE.getAddExpr(BackedgeTakenCount, One);
|
|
if (IterationCount != SE.getSCEV(Sel)) return Cond;
|
|
|
|
// Check for a max calculation that matches the pattern. There's no check
|
|
// for ICMP_ULE here because the comparison would be with zero, which
|
|
// isn't interesting.
|
|
CmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE;
|
|
const SCEVNAryExpr *Max = 0;
|
|
if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(BackedgeTakenCount)) {
|
|
Pred = ICmpInst::ICMP_SLE;
|
|
Max = S;
|
|
} else if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(IterationCount)) {
|
|
Pred = ICmpInst::ICMP_SLT;
|
|
Max = S;
|
|
} else if (const SCEVUMaxExpr *U = dyn_cast<SCEVUMaxExpr>(IterationCount)) {
|
|
Pred = ICmpInst::ICMP_ULT;
|
|
Max = U;
|
|
} else {
|
|
// No match; bail.
|
|
return Cond;
|
|
}
|
|
|
|
// To handle a max with more than two operands, this optimization would
|
|
// require additional checking and setup.
|
|
if (Max->getNumOperands() != 2)
|
|
return Cond;
|
|
|
|
const SCEV *MaxLHS = Max->getOperand(0);
|
|
const SCEV *MaxRHS = Max->getOperand(1);
|
|
|
|
// ScalarEvolution canonicalizes constants to the left. For < and >, look
|
|
// for a comparison with 1. For <= and >=, a comparison with zero.
|
|
if (!MaxLHS ||
|
|
(ICmpInst::isTrueWhenEqual(Pred) ? !MaxLHS->isZero() : (MaxLHS != One)))
|
|
return Cond;
|
|
|
|
// Check the relevant induction variable for conformance to
|
|
// the pattern.
|
|
const SCEV *IV = SE.getSCEV(Cond->getOperand(0));
|
|
const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
|
|
if (!AR || !AR->isAffine() ||
|
|
AR->getStart() != One ||
|
|
AR->getStepRecurrence(SE) != One)
|
|
return Cond;
|
|
|
|
assert(AR->getLoop() == L &&
|
|
"Loop condition operand is an addrec in a different loop!");
|
|
|
|
// Check the right operand of the select, and remember it, as it will
|
|
// be used in the new comparison instruction.
|
|
Value *NewRHS = 0;
|
|
if (ICmpInst::isTrueWhenEqual(Pred)) {
|
|
// Look for n+1, and grab n.
|
|
if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1)))
|
|
if (isa<ConstantInt>(BO->getOperand(1)) &&
|
|
cast<ConstantInt>(BO->getOperand(1))->isOne() &&
|
|
SE.getSCEV(BO->getOperand(0)) == MaxRHS)
|
|
NewRHS = BO->getOperand(0);
|
|
if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2)))
|
|
if (isa<ConstantInt>(BO->getOperand(1)) &&
|
|
cast<ConstantInt>(BO->getOperand(1))->isOne() &&
|
|
SE.getSCEV(BO->getOperand(0)) == MaxRHS)
|
|
NewRHS = BO->getOperand(0);
|
|
if (!NewRHS)
|
|
return Cond;
|
|
} else if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS)
|
|
NewRHS = Sel->getOperand(1);
|
|
else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS)
|
|
NewRHS = Sel->getOperand(2);
|
|
else
|
|
llvm_unreachable("Max doesn't match expected pattern!");
|
|
|
|
// Determine the new comparison opcode. It may be signed or unsigned,
|
|
// and the original comparison may be either equality or inequality.
|
|
if (Cond->getPredicate() == CmpInst::ICMP_EQ)
|
|
Pred = CmpInst::getInversePredicate(Pred);
|
|
|
|
// Ok, everything looks ok to change the condition into an SLT or SGE and
|
|
// delete the max calculation.
|
|
ICmpInst *NewCond =
|
|
new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp");
|
|
|
|
// Delete the max calculation instructions.
|
|
Cond->replaceAllUsesWith(NewCond);
|
|
CondUse->setUser(NewCond);
|
|
Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
|
|
Cond->eraseFromParent();
|
|
Sel->eraseFromParent();
|
|
if (Cmp->use_empty())
|
|
Cmp->eraseFromParent();
|
|
return NewCond;
|
|
}
|
|
|
|
/// OptimizeLoopTermCond - Change loop terminating condition to use the
|
|
/// postinc iv when possible.
|
|
void
|
|
LSRInstance::OptimizeLoopTermCond() {
|
|
SmallPtrSet<Instruction *, 4> PostIncs;
|
|
|
|
BasicBlock *LatchBlock = L->getLoopLatch();
|
|
SmallVector<BasicBlock*, 8> ExitingBlocks;
|
|
L->getExitingBlocks(ExitingBlocks);
|
|
|
|
for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
|
|
BasicBlock *ExitingBlock = ExitingBlocks[i];
|
|
|
|
// Get the terminating condition for the loop if possible. If we
|
|
// can, we want to change it to use a post-incremented version of its
|
|
// induction variable, to allow coalescing the live ranges for the IV into
|
|
// one register value.
|
|
|
|
BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
|
|
if (!TermBr)
|
|
continue;
|
|
// FIXME: Overly conservative, termination condition could be an 'or' etc..
|
|
if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition()))
|
|
continue;
|
|
|
|
// Search IVUsesByStride to find Cond's IVUse if there is one.
|
|
IVStrideUse *CondUse = 0;
|
|
ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition());
|
|
if (!FindIVUserForCond(Cond, CondUse))
|
|
continue;
|
|
|
|
// If the trip count is computed in terms of a max (due to ScalarEvolution
|
|
// being unable to find a sufficient guard, for example), change the loop
|
|
// comparison to use SLT or ULT instead of NE.
|
|
// One consequence of doing this now is that it disrupts the count-down
|
|
// optimization. That's not always a bad thing though, because in such
|
|
// cases it may still be worthwhile to avoid a max.
|
|
Cond = OptimizeMax(Cond, CondUse);
|
|
|
|
// If this exiting block dominates the latch block, it may also use
|
|
// the post-inc value if it won't be shared with other uses.
|
|
// Check for dominance.
|
|
if (!DT.dominates(ExitingBlock, LatchBlock))
|
|
continue;
|
|
|
|
// Conservatively avoid trying to use the post-inc value in non-latch
|
|
// exits if there may be pre-inc users in intervening blocks.
|
|
if (LatchBlock != ExitingBlock)
|
|
for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
|
|
// Test if the use is reachable from the exiting block. This dominator
|
|
// query is a conservative approximation of reachability.
|
|
if (&*UI != CondUse &&
|
|
!DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) {
|
|
// Conservatively assume there may be reuse if the quotient of their
|
|
// strides could be a legal scale.
|
|
const SCEV *A = IU.getStride(*CondUse, L);
|
|
const SCEV *B = IU.getStride(*UI, L);
|
|
if (!A || !B) continue;
|
|
if (SE.getTypeSizeInBits(A->getType()) !=
|
|
SE.getTypeSizeInBits(B->getType())) {
|
|
if (SE.getTypeSizeInBits(A->getType()) >
|
|
SE.getTypeSizeInBits(B->getType()))
|
|
B = SE.getSignExtendExpr(B, A->getType());
|
|
else
|
|
A = SE.getSignExtendExpr(A, B->getType());
|
|
}
|
|
if (const SCEVConstant *D =
|
|
dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) {
|
|
const ConstantInt *C = D->getValue();
|
|
// Stride of one or negative one can have reuse with non-addresses.
|
|
if (C->isOne() || C->isAllOnesValue())
|
|
goto decline_post_inc;
|
|
// Avoid weird situations.
|
|
if (C->getValue().getMinSignedBits() >= 64 ||
|
|
C->getValue().isMinSignedValue())
|
|
goto decline_post_inc;
|
|
// Without TLI, assume that any stride might be valid, and so any
|
|
// use might be shared.
|
|
if (!TLI)
|
|
goto decline_post_inc;
|
|
// Check for possible scaled-address reuse.
|
|
const Type *AccessTy = getAccessType(UI->getUser());
|
|
TargetLowering::AddrMode AM;
|
|
AM.Scale = C->getSExtValue();
|
|
if (TLI->isLegalAddressingMode(AM, AccessTy))
|
|
goto decline_post_inc;
|
|
AM.Scale = -AM.Scale;
|
|
if (TLI->isLegalAddressingMode(AM, AccessTy))
|
|
goto decline_post_inc;
|
|
}
|
|
}
|
|
|
|
DEBUG(dbgs() << " Change loop exiting icmp to use postinc iv: "
|
|
<< *Cond << '\n');
|
|
|
|
// It's possible for the setcc instruction to be anywhere in the loop, and
|
|
// possible for it to have multiple users. If it is not immediately before
|
|
// the exiting block branch, move it.
|
|
if (&*++BasicBlock::iterator(Cond) != TermBr) {
|
|
if (Cond->hasOneUse()) {
|
|
Cond->moveBefore(TermBr);
|
|
} else {
|
|
// Clone the terminating condition and insert into the loopend.
|
|
ICmpInst *OldCond = Cond;
|
|
Cond = cast<ICmpInst>(Cond->clone());
|
|
Cond->setName(L->getHeader()->getName() + ".termcond");
|
|
ExitingBlock->getInstList().insert(TermBr, Cond);
|
|
|
|
// Clone the IVUse, as the old use still exists!
|
|
CondUse = &IU.AddUser(Cond, CondUse->getOperandValToReplace());
|
|
TermBr->replaceUsesOfWith(OldCond, Cond);
|
|
}
|
|
}
|
|
|
|
// If we get to here, we know that we can transform the setcc instruction to
|
|
// use the post-incremented version of the IV, allowing us to coalesce the
|
|
// live ranges for the IV correctly.
|
|
CondUse->transformToPostInc(L);
|
|
Changed = true;
|
|
|
|
PostIncs.insert(Cond);
|
|
decline_post_inc:;
|
|
}
|
|
|
|
// Determine an insertion point for the loop induction variable increment. It
|
|
// must dominate all the post-inc comparisons we just set up, and it must
|
|
// dominate the loop latch edge.
|
|
IVIncInsertPos = L->getLoopLatch()->getTerminator();
|
|
for (SmallPtrSet<Instruction *, 4>::const_iterator I = PostIncs.begin(),
|
|
E = PostIncs.end(); I != E; ++I) {
|
|
BasicBlock *BB =
|
|
DT.findNearestCommonDominator(IVIncInsertPos->getParent(),
|
|
(*I)->getParent());
|
|
if (BB == (*I)->getParent())
|
|
IVIncInsertPos = *I;
|
|
else if (BB != IVIncInsertPos->getParent())
|
|
IVIncInsertPos = BB->getTerminator();
|
|
}
|
|
}
|
|
|
|
/// reconcileNewOffset - Determine if the given use can accomodate a fixup
|
|
/// at the given offset and other details. If so, update the use and
|
|
/// return true.
|
|
bool
|
|
LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
|
|
LSRUse::KindType Kind, const Type *AccessTy) {
|
|
int64_t NewMinOffset = LU.MinOffset;
|
|
int64_t NewMaxOffset = LU.MaxOffset;
|
|
const Type *NewAccessTy = AccessTy;
|
|
|
|
// Check for a mismatched kind. It's tempting to collapse mismatched kinds to
|
|
// something conservative, however this can pessimize in the case that one of
|
|
// the uses will have all its uses outside the loop, for example.
|
|
if (LU.Kind != Kind)
|
|
return false;
|
|
// Conservatively assume HasBaseReg is true for now.
|
|
if (NewOffset < LU.MinOffset) {
|
|
if (!isAlwaysFoldable(LU.MaxOffset - NewOffset, 0, HasBaseReg,
|
|
Kind, AccessTy, TLI))
|
|
return false;
|
|
NewMinOffset = NewOffset;
|
|
} else if (NewOffset > LU.MaxOffset) {
|
|
if (!isAlwaysFoldable(NewOffset - LU.MinOffset, 0, HasBaseReg,
|
|
Kind, AccessTy, TLI))
|
|
return false;
|
|
NewMaxOffset = NewOffset;
|
|
}
|
|
// Check for a mismatched access type, and fall back conservatively as needed.
|
|
if (Kind == LSRUse::Address && AccessTy != LU.AccessTy)
|
|
NewAccessTy = Type::getVoidTy(AccessTy->getContext());
|
|
|
|
// Update the use.
|
|
LU.MinOffset = NewMinOffset;
|
|
LU.MaxOffset = NewMaxOffset;
|
|
LU.AccessTy = NewAccessTy;
|
|
if (NewOffset != LU.Offsets.back())
|
|
LU.Offsets.push_back(NewOffset);
|
|
return true;
|
|
}
|
|
|
|
/// getUse - Return an LSRUse index and an offset value for a fixup which
|
|
/// needs the given expression, with the given kind and optional access type.
|
|
/// Either reuse an existing use or create a new one, as needed.
|
|
std::pair<size_t, int64_t>
|
|
LSRInstance::getUse(const SCEV *&Expr,
|
|
LSRUse::KindType Kind, const Type *AccessTy) {
|
|
const SCEV *Copy = Expr;
|
|
int64_t Offset = ExtractImmediate(Expr, SE);
|
|
|
|
// Basic uses can't accept any offset, for example.
|
|
if (!isAlwaysFoldable(Offset, 0, /*HasBaseReg=*/true, Kind, AccessTy, TLI)) {
|
|
Expr = Copy;
|
|
Offset = 0;
|
|
}
|
|
|
|
std::pair<UseMapTy::iterator, bool> P =
|
|
UseMap.insert(std::make_pair(Expr, 0));
|
|
if (!P.second) {
|
|
// A use already existed with this base.
|
|
size_t LUIdx = P.first->second;
|
|
LSRUse &LU = Uses[LUIdx];
|
|
if (reconcileNewOffset(LU, Offset, /*HasBaseReg=*/true, Kind, AccessTy))
|
|
// Reuse this use.
|
|
return std::make_pair(LUIdx, Offset);
|
|
}
|
|
|
|
// Create a new use.
|
|
size_t LUIdx = Uses.size();
|
|
P.first->second = LUIdx;
|
|
Uses.push_back(LSRUse(Kind, AccessTy));
|
|
LSRUse &LU = Uses[LUIdx];
|
|
|
|
// We don't need to track redundant offsets, but we don't need to go out
|
|
// of our way here to avoid them.
|
|
if (LU.Offsets.empty() || Offset != LU.Offsets.back())
|
|
LU.Offsets.push_back(Offset);
|
|
|
|
LU.MinOffset = Offset;
|
|
LU.MaxOffset = Offset;
|
|
return std::make_pair(LUIdx, Offset);
|
|
}
|
|
|
|
/// DeleteUse - Delete the given use from the Uses list.
|
|
void LSRInstance::DeleteUse(LSRUse &LU) {
|
|
if (&LU != &Uses.back())
|
|
std::swap(LU, Uses.back());
|
|
Uses.pop_back();
|
|
}
|
|
|
|
/// FindUseWithFormula - Look for a use distinct from OrigLU which is has
|
|
/// a formula that has the same registers as the given formula.
|
|
LSRUse *
|
|
LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF,
|
|
const LSRUse &OrigLU) {
|
|
// Search all uses for the formula. This could be more clever. Ignore
|
|
// ICmpZero uses because they may contain formulae generated by
|
|
// GenerateICmpZeroScales, in which case adding fixup offsets may
|
|
// be invalid.
|
|
for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
|
|
LSRUse &LU = Uses[LUIdx];
|
|
if (&LU != &OrigLU &&
|
|
LU.Kind != LSRUse::ICmpZero &&
|
|
LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy &&
|
|
LU.HasFormulaWithSameRegs(OrigF)) {
|
|
for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
|
|
E = LU.Formulae.end(); I != E; ++I) {
|
|
const Formula &F = *I;
|
|
if (F.BaseRegs == OrigF.BaseRegs &&
|
|
F.ScaledReg == OrigF.ScaledReg &&
|
|
F.AM.BaseGV == OrigF.AM.BaseGV &&
|
|
F.AM.Scale == OrigF.AM.Scale &&
|
|
LU.Kind) {
|
|
if (F.AM.BaseOffs == 0)
|
|
return &LU;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
void LSRInstance::CollectInterestingTypesAndFactors() {
|
|
SmallSetVector<const SCEV *, 4> Strides;
|
|
|
|
// Collect interesting types and strides.
|
|
SmallVector<const SCEV *, 4> Worklist;
|
|
for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
|
|
const SCEV *Expr = IU.getExpr(*UI);
|
|
|
|
// Collect interesting types.
|
|
Types.insert(SE.getEffectiveSCEVType(Expr->getType()));
|
|
|
|
// Add strides for mentioned loops.
|
|
Worklist.push_back(Expr);
|
|
do {
|
|
const SCEV *S = Worklist.pop_back_val();
|
|
if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
|
|
Strides.insert(AR->getStepRecurrence(SE));
|
|
Worklist.push_back(AR->getStart());
|
|
} else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
|
|
Worklist.insert(Worklist.end(), Add->op_begin(), Add->op_end());
|
|
}
|
|
} while (!Worklist.empty());
|
|
}
|
|
|
|
// Compute interesting factors from the set of interesting strides.
|
|
for (SmallSetVector<const SCEV *, 4>::const_iterator
|
|
I = Strides.begin(), E = Strides.end(); I != E; ++I)
|
|
for (SmallSetVector<const SCEV *, 4>::const_iterator NewStrideIter =
|
|
next(I); NewStrideIter != E; ++NewStrideIter) {
|
|
const SCEV *OldStride = *I;
|
|
const SCEV *NewStride = *NewStrideIter;
|
|
|
|
if (SE.getTypeSizeInBits(OldStride->getType()) !=
|
|
SE.getTypeSizeInBits(NewStride->getType())) {
|
|
if (SE.getTypeSizeInBits(OldStride->getType()) >
|
|
SE.getTypeSizeInBits(NewStride->getType()))
|
|
NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType());
|
|
else
|
|
OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType());
|
|
}
|
|
if (const SCEVConstant *Factor =
|
|
dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride,
|
|
SE, true))) {
|
|
if (Factor->getValue()->getValue().getMinSignedBits() <= 64)
|
|
Factors.insert(Factor->getValue()->getValue().getSExtValue());
|
|
} else if (const SCEVConstant *Factor =
|
|
dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride,
|
|
NewStride,
|
|
SE, true))) {
|
|
if (Factor->getValue()->getValue().getMinSignedBits() <= 64)
|
|
Factors.insert(Factor->getValue()->getValue().getSExtValue());
|
|
}
|
|
}
|
|
|
|
// If all uses use the same type, don't bother looking for truncation-based
|
|
// reuse.
|
|
if (Types.size() == 1)
|
|
Types.clear();
|
|
|
|
DEBUG(print_factors_and_types(dbgs()));
|
|
}
|
|
|
|
void LSRInstance::CollectFixupsAndInitialFormulae() {
|
|
for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
|
|
// Record the uses.
|
|
LSRFixup &LF = getNewFixup();
|
|
LF.UserInst = UI->getUser();
|
|
LF.OperandValToReplace = UI->getOperandValToReplace();
|
|
LF.PostIncLoops = UI->getPostIncLoops();
|
|
|
|
LSRUse::KindType Kind = LSRUse::Basic;
|
|
const Type *AccessTy = 0;
|
|
if (isAddressUse(LF.UserInst, LF.OperandValToReplace)) {
|
|
Kind = LSRUse::Address;
|
|
AccessTy = getAccessType(LF.UserInst);
|
|
}
|
|
|
|
const SCEV *S = IU.getExpr(*UI);
|
|
|
|
// Equality (== and !=) ICmps are special. We can rewrite (i == N) as
|
|
// (N - i == 0), and this allows (N - i) to be the expression that we work
|
|
// with rather than just N or i, so we can consider the register
|
|
// requirements for both N and i at the same time. Limiting this code to
|
|
// equality icmps is not a problem because all interesting loops use
|
|
// equality icmps, thanks to IndVarSimplify.
|
|
if (ICmpInst *CI = dyn_cast<ICmpInst>(LF.UserInst))
|
|
if (CI->isEquality()) {
|
|
// Swap the operands if needed to put the OperandValToReplace on the
|
|
// left, for consistency.
|
|
Value *NV = CI->getOperand(1);
|
|
if (NV == LF.OperandValToReplace) {
|
|
CI->setOperand(1, CI->getOperand(0));
|
|
CI->setOperand(0, NV);
|
|
NV = CI->getOperand(1);
|
|
Changed = true;
|
|
}
|
|
|
|
// x == y --> x - y == 0
|
|
const SCEV *N = SE.getSCEV(NV);
|
|
if (N->isLoopInvariant(L)) {
|
|
Kind = LSRUse::ICmpZero;
|
|
S = SE.getMinusSCEV(N, S);
|
|
}
|
|
|
|
// -1 and the negations of all interesting strides (except the negation
|
|
// of -1) are now also interesting.
|
|
for (size_t i = 0, e = Factors.size(); i != e; ++i)
|
|
if (Factors[i] != -1)
|
|
Factors.insert(-(uint64_t)Factors[i]);
|
|
Factors.insert(-1);
|
|
}
|
|
|
|
// Set up the initial formula for this use.
|
|
std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy);
|
|
LF.LUIdx = P.first;
|
|
LF.Offset = P.second;
|
|
LSRUse &LU = Uses[LF.LUIdx];
|
|
LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
|
|
|
|
// If this is the first use of this LSRUse, give it a formula.
|
|
if (LU.Formulae.empty()) {
|
|
InsertInitialFormula(S, LU, LF.LUIdx);
|
|
CountRegisters(LU.Formulae.back(), LF.LUIdx);
|
|
}
|
|
}
|
|
|
|
DEBUG(print_fixups(dbgs()));
|
|
}
|
|
|
|
/// InsertInitialFormula - Insert a formula for the given expression into
|
|
/// the given use, separating out loop-variant portions from loop-invariant
|
|
/// and loop-computable portions.
|
|
void
|
|
LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) {
|
|
Formula F;
|
|
F.InitialMatch(S, L, SE, DT);
|
|
bool Inserted = InsertFormula(LU, LUIdx, F);
|
|
assert(Inserted && "Initial formula already exists!"); (void)Inserted;
|
|
}
|
|
|
|
/// InsertSupplementalFormula - Insert a simple single-register formula for
|
|
/// the given expression into the given use.
|
|
void
|
|
LSRInstance::InsertSupplementalFormula(const SCEV *S,
|
|
LSRUse &LU, size_t LUIdx) {
|
|
Formula F;
|
|
F.BaseRegs.push_back(S);
|
|
F.AM.HasBaseReg = true;
|
|
bool Inserted = InsertFormula(LU, LUIdx, F);
|
|
assert(Inserted && "Supplemental formula already exists!"); (void)Inserted;
|
|
}
|
|
|
|
/// CountRegisters - Note which registers are used by the given formula,
|
|
/// updating RegUses.
|
|
void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) {
|
|
if (F.ScaledReg)
|
|
RegUses.CountRegister(F.ScaledReg, LUIdx);
|
|
for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
|
|
E = F.BaseRegs.end(); I != E; ++I)
|
|
RegUses.CountRegister(*I, LUIdx);
|
|
}
|
|
|
|
/// InsertFormula - If the given formula has not yet been inserted, add it to
|
|
/// the list, and return true. Return false otherwise.
|
|
bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) {
|
|
if (!LU.InsertFormula(F))
|
|
return false;
|
|
|
|
CountRegisters(F, LUIdx);
|
|
return true;
|
|
}
|
|
|
|
/// CollectLoopInvariantFixupsAndFormulae - Check for other uses of
|
|
/// loop-invariant values which we're tracking. These other uses will pin these
|
|
/// values in registers, making them less profitable for elimination.
|
|
/// TODO: This currently misses non-constant addrec step registers.
|
|
/// TODO: Should this give more weight to users inside the loop?
|
|
void
|
|
LSRInstance::CollectLoopInvariantFixupsAndFormulae() {
|
|
SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end());
|
|
SmallPtrSet<const SCEV *, 8> Inserted;
|
|
|
|
while (!Worklist.empty()) {
|
|
const SCEV *S = Worklist.pop_back_val();
|
|
|
|
if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S))
|
|
Worklist.insert(Worklist.end(), N->op_begin(), N->op_end());
|
|
else if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S))
|
|
Worklist.push_back(C->getOperand());
|
|
else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
|
|
Worklist.push_back(D->getLHS());
|
|
Worklist.push_back(D->getRHS());
|
|
} else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
|
|
if (!Inserted.insert(U)) continue;
|
|
const Value *V = U->getValue();
|
|
if (const Instruction *Inst = dyn_cast<Instruction>(V)) {
|
|
// Look for instructions defined outside the loop.
|
|
if (L->contains(Inst)) continue;
|
|
} else if (isa<UndefValue>(V))
|
|
// Undef doesn't have a live range, so it doesn't matter.
|
|
continue;
|
|
for (Value::const_use_iterator UI = V->use_begin(), UE = V->use_end();
|
|
UI != UE; ++UI) {
|
|
const Instruction *UserInst = dyn_cast<Instruction>(*UI);
|
|
// Ignore non-instructions.
|
|
if (!UserInst)
|
|
continue;
|
|
// Ignore instructions in other functions (as can happen with
|
|
// Constants).
|
|
if (UserInst->getParent()->getParent() != L->getHeader()->getParent())
|
|
continue;
|
|
// Ignore instructions not dominated by the loop.
|
|
const BasicBlock *UseBB = !isa<PHINode>(UserInst) ?
|
|
UserInst->getParent() :
|
|
cast<PHINode>(UserInst)->getIncomingBlock(
|
|
PHINode::getIncomingValueNumForOperand(UI.getOperandNo()));
|
|
if (!DT.dominates(L->getHeader(), UseBB))
|
|
continue;
|
|
// Ignore uses which are part of other SCEV expressions, to avoid
|
|
// analyzing them multiple times.
|
|
if (SE.isSCEVable(UserInst->getType())) {
|
|
const SCEV *UserS = SE.getSCEV(const_cast<Instruction *>(UserInst));
|
|
// If the user is a no-op, look through to its uses.
|
|
if (!isa<SCEVUnknown>(UserS))
|
|
continue;
|
|
if (UserS == U) {
|
|
Worklist.push_back(
|
|
SE.getUnknown(const_cast<Instruction *>(UserInst)));
|
|
continue;
|
|
}
|
|
}
|
|
// Ignore icmp instructions which are already being analyzed.
|
|
if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) {
|
|
unsigned OtherIdx = !UI.getOperandNo();
|
|
Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx));
|
|
if (SE.getSCEV(OtherOp)->hasComputableLoopEvolution(L))
|
|
continue;
|
|
}
|
|
|
|
LSRFixup &LF = getNewFixup();
|
|
LF.UserInst = const_cast<Instruction *>(UserInst);
|
|
LF.OperandValToReplace = UI.getUse();
|
|
std::pair<size_t, int64_t> P = getUse(S, LSRUse::Basic, 0);
|
|
LF.LUIdx = P.first;
|
|
LF.Offset = P.second;
|
|
LSRUse &LU = Uses[LF.LUIdx];
|
|
LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
|
|
InsertSupplementalFormula(U, LU, LF.LUIdx);
|
|
CountRegisters(LU.Formulae.back(), Uses.size() - 1);
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/// CollectSubexprs - Split S into subexpressions which can be pulled out into
|
|
/// separate registers. If C is non-null, multiply each subexpression by C.
|
|
static void CollectSubexprs(const SCEV *S, const SCEVConstant *C,
|
|
SmallVectorImpl<const SCEV *> &Ops,
|
|
ScalarEvolution &SE) {
|
|
if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
|
|
// Break out add operands.
|
|
for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
|
|
I != E; ++I)
|
|
CollectSubexprs(*I, C, Ops, SE);
|
|
return;
|
|
} else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
|
|
// Split a non-zero base out of an addrec.
|
|
if (!AR->getStart()->isZero()) {
|
|
CollectSubexprs(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
|
|
AR->getStepRecurrence(SE),
|
|
AR->getLoop()), C, Ops, SE);
|
|
CollectSubexprs(AR->getStart(), C, Ops, SE);
|
|
return;
|
|
}
|
|
} else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
|
|
// Break (C * (a + b + c)) into C*a + C*b + C*c.
|
|
if (Mul->getNumOperands() == 2)
|
|
if (const SCEVConstant *Op0 =
|
|
dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
|
|
CollectSubexprs(Mul->getOperand(1),
|
|
C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0,
|
|
Ops, SE);
|
|
return;
|
|
}
|
|
}
|
|
|
|
// Otherwise use the value itself.
|
|
Ops.push_back(C ? SE.getMulExpr(C, S) : S);
|
|
}
|
|
|
|
/// GenerateReassociations - Split out subexpressions from adds and the bases of
|
|
/// addrecs.
|
|
void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx,
|
|
Formula Base,
|
|
unsigned Depth) {
|
|
// Arbitrarily cap recursion to protect compile time.
|
|
if (Depth >= 3) return;
|
|
|
|
for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
|
|
const SCEV *BaseReg = Base.BaseRegs[i];
|
|
|
|
SmallVector<const SCEV *, 8> AddOps;
|
|
CollectSubexprs(BaseReg, 0, AddOps, SE);
|
|
if (AddOps.size() == 1) continue;
|
|
|
|
for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(),
|
|
JE = AddOps.end(); J != JE; ++J) {
|
|
// Don't pull a constant into a register if the constant could be folded
|
|
// into an immediate field.
|
|
if (isAlwaysFoldable(*J, LU.MinOffset, LU.MaxOffset,
|
|
Base.getNumRegs() > 1,
|
|
LU.Kind, LU.AccessTy, TLI, SE))
|
|
continue;
|
|
|
|
// Collect all operands except *J.
|
|
SmallVector<const SCEV *, 8> InnerAddOps;
|
|
for (SmallVectorImpl<const SCEV *>::const_iterator K = AddOps.begin(),
|
|
KE = AddOps.end(); K != KE; ++K)
|
|
if (K != J)
|
|
InnerAddOps.push_back(*K);
|
|
|
|
// Don't leave just a constant behind in a register if the constant could
|
|
// be folded into an immediate field.
|
|
if (InnerAddOps.size() == 1 &&
|
|
isAlwaysFoldable(InnerAddOps[0], LU.MinOffset, LU.MaxOffset,
|
|
Base.getNumRegs() > 1,
|
|
LU.Kind, LU.AccessTy, TLI, SE))
|
|
continue;
|
|
|
|
const SCEV *InnerSum = SE.getAddExpr(InnerAddOps);
|
|
if (InnerSum->isZero())
|
|
continue;
|
|
Formula F = Base;
|
|
F.BaseRegs[i] = InnerSum;
|
|
F.BaseRegs.push_back(*J);
|
|
if (InsertFormula(LU, LUIdx, F))
|
|
// If that formula hadn't been seen before, recurse to find more like
|
|
// it.
|
|
GenerateReassociations(LU, LUIdx, LU.Formulae.back(), Depth+1);
|
|
}
|
|
}
|
|
}
|
|
|
|
/// GenerateCombinations - Generate a formula consisting of all of the
|
|
/// loop-dominating registers added into a single register.
|
|
void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx,
|
|
Formula Base) {
|
|
// This method is only interesting on a plurality of registers.
|
|
if (Base.BaseRegs.size() <= 1) return;
|
|
|
|
Formula F = Base;
|
|
F.BaseRegs.clear();
|
|
SmallVector<const SCEV *, 4> Ops;
|
|
for (SmallVectorImpl<const SCEV *>::const_iterator
|
|
I = Base.BaseRegs.begin(), E = Base.BaseRegs.end(); I != E; ++I) {
|
|
const SCEV *BaseReg = *I;
|
|
if (BaseReg->properlyDominates(L->getHeader(), &DT) &&
|
|
!BaseReg->hasComputableLoopEvolution(L))
|
|
Ops.push_back(BaseReg);
|
|
else
|
|
F.BaseRegs.push_back(BaseReg);
|
|
}
|
|
if (Ops.size() > 1) {
|
|
const SCEV *Sum = SE.getAddExpr(Ops);
|
|
// TODO: If Sum is zero, it probably means ScalarEvolution missed an
|
|
// opportunity to fold something. For now, just ignore such cases
|
|
// rather than proceed with zero in a register.
|
|
if (!Sum->isZero()) {
|
|
F.BaseRegs.push_back(Sum);
|
|
(void)InsertFormula(LU, LUIdx, F);
|
|
}
|
|
}
|
|
}
|
|
|
|
/// GenerateSymbolicOffsets - Generate reuse formulae using symbolic offsets.
|
|
void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx,
|
|
Formula Base) {
|
|
// We can't add a symbolic offset if the address already contains one.
|
|
if (Base.AM.BaseGV) return;
|
|
|
|
for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
|
|
const SCEV *G = Base.BaseRegs[i];
|
|
GlobalValue *GV = ExtractSymbol(G, SE);
|
|
if (G->isZero() || !GV)
|
|
continue;
|
|
Formula F = Base;
|
|
F.AM.BaseGV = GV;
|
|
if (!isLegalUse(F.AM, LU.MinOffset, LU.MaxOffset,
|
|
LU.Kind, LU.AccessTy, TLI))
|
|
continue;
|
|
F.BaseRegs[i] = G;
|
|
(void)InsertFormula(LU, LUIdx, F);
|
|
}
|
|
}
|
|
|
|
/// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets.
|
|
void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx,
|
|
Formula Base) {
|
|
// TODO: For now, just add the min and max offset, because it usually isn't
|
|
// worthwhile looking at everything inbetween.
|
|
SmallVector<int64_t, 4> Worklist;
|
|
Worklist.push_back(LU.MinOffset);
|
|
if (LU.MaxOffset != LU.MinOffset)
|
|
Worklist.push_back(LU.MaxOffset);
|
|
|
|
for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
|
|
const SCEV *G = Base.BaseRegs[i];
|
|
|
|
for (SmallVectorImpl<int64_t>::const_iterator I = Worklist.begin(),
|
|
E = Worklist.end(); I != E; ++I) {
|
|
Formula F = Base;
|
|
F.AM.BaseOffs = (uint64_t)Base.AM.BaseOffs - *I;
|
|
if (isLegalUse(F.AM, LU.MinOffset - *I, LU.MaxOffset - *I,
|
|
LU.Kind, LU.AccessTy, TLI)) {
|
|
F.BaseRegs[i] = SE.getAddExpr(G, SE.getConstant(G->getType(), *I));
|
|
|
|
(void)InsertFormula(LU, LUIdx, F);
|
|
}
|
|
}
|
|
|
|
int64_t Imm = ExtractImmediate(G, SE);
|
|
if (G->isZero() || Imm == 0)
|
|
continue;
|
|
Formula F = Base;
|
|
F.AM.BaseOffs = (uint64_t)F.AM.BaseOffs + Imm;
|
|
if (!isLegalUse(F.AM, LU.MinOffset, LU.MaxOffset,
|
|
LU.Kind, LU.AccessTy, TLI))
|
|
continue;
|
|
F.BaseRegs[i] = G;
|
|
(void)InsertFormula(LU, LUIdx, F);
|
|
}
|
|
}
|
|
|
|
/// GenerateICmpZeroScales - For ICmpZero, check to see if we can scale up
|
|
/// the comparison. For example, x == y -> x*c == y*c.
|
|
void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx,
|
|
Formula Base) {
|
|
if (LU.Kind != LSRUse::ICmpZero) return;
|
|
|
|
// Determine the integer type for the base formula.
|
|
const Type *IntTy = Base.getType();
|
|
if (!IntTy) return;
|
|
if (SE.getTypeSizeInBits(IntTy) > 64) return;
|
|
|
|
// Don't do this if there is more than one offset.
|
|
if (LU.MinOffset != LU.MaxOffset) return;
|
|
|
|
assert(!Base.AM.BaseGV && "ICmpZero use is not legal!");
|
|
|
|
// Check each interesting stride.
|
|
for (SmallSetVector<int64_t, 8>::const_iterator
|
|
I = Factors.begin(), E = Factors.end(); I != E; ++I) {
|
|
int64_t Factor = *I;
|
|
Formula F = Base;
|
|
|
|
// Check that the multiplication doesn't overflow.
|
|
if (F.AM.BaseOffs == INT64_MIN && Factor == -1)
|
|
continue;
|
|
F.AM.BaseOffs = (uint64_t)Base.AM.BaseOffs * Factor;
|
|
if (F.AM.BaseOffs / Factor != Base.AM.BaseOffs)
|
|
continue;
|
|
|
|
// Check that multiplying with the use offset doesn't overflow.
|
|
int64_t Offset = LU.MinOffset;
|
|
if (Offset == INT64_MIN && Factor == -1)
|
|
continue;
|
|
Offset = (uint64_t)Offset * Factor;
|
|
if (Offset / Factor != LU.MinOffset)
|
|
continue;
|
|
|
|
// Check that this scale is legal.
|
|
if (!isLegalUse(F.AM, Offset, Offset, LU.Kind, LU.AccessTy, TLI))
|
|
continue;
|
|
|
|
// Compensate for the use having MinOffset built into it.
|
|
F.AM.BaseOffs = (uint64_t)F.AM.BaseOffs + Offset - LU.MinOffset;
|
|
|
|
const SCEV *FactorS = SE.getConstant(IntTy, Factor);
|
|
|
|
// Check that multiplying with each base register doesn't overflow.
|
|
for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) {
|
|
F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS);
|
|
if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i])
|
|
goto next;
|
|
}
|
|
|
|
// Check that multiplying with the scaled register doesn't overflow.
|
|
if (F.ScaledReg) {
|
|
F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS);
|
|
if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg)
|
|
continue;
|
|
}
|
|
|
|
// If we make it here and it's legal, add it.
|
|
(void)InsertFormula(LU, LUIdx, F);
|
|
next:;
|
|
}
|
|
}
|
|
|
|
/// GenerateScales - Generate stride factor reuse formulae by making use of
|
|
/// scaled-offset address modes, for example.
|
|
void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base) {
|
|
// Determine the integer type for the base formula.
|
|
const Type *IntTy = Base.getType();
|
|
if (!IntTy) return;
|
|
|
|
// If this Formula already has a scaled register, we can't add another one.
|
|
if (Base.AM.Scale != 0) return;
|
|
|
|
// Check each interesting stride.
|
|
for (SmallSetVector<int64_t, 8>::const_iterator
|
|
I = Factors.begin(), E = Factors.end(); I != E; ++I) {
|
|
int64_t Factor = *I;
|
|
|
|
Base.AM.Scale = Factor;
|
|
Base.AM.HasBaseReg = Base.BaseRegs.size() > 1;
|
|
// Check whether this scale is going to be legal.
|
|
if (!isLegalUse(Base.AM, LU.MinOffset, LU.MaxOffset,
|
|
LU.Kind, LU.AccessTy, TLI)) {
|
|
// As a special-case, handle special out-of-loop Basic users specially.
|
|
// TODO: Reconsider this special case.
|
|
if (LU.Kind == LSRUse::Basic &&
|
|
isLegalUse(Base.AM, LU.MinOffset, LU.MaxOffset,
|
|
LSRUse::Special, LU.AccessTy, TLI) &&
|
|
LU.AllFixupsOutsideLoop)
|
|
LU.Kind = LSRUse::Special;
|
|
else
|
|
continue;
|
|
}
|
|
// For an ICmpZero, negating a solitary base register won't lead to
|
|
// new solutions.
|
|
if (LU.Kind == LSRUse::ICmpZero &&
|
|
!Base.AM.HasBaseReg && Base.AM.BaseOffs == 0 && !Base.AM.BaseGV)
|
|
continue;
|
|
// For each addrec base reg, apply the scale, if possible.
|
|
for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
|
|
if (const SCEVAddRecExpr *AR =
|
|
dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i])) {
|
|
const SCEV *FactorS = SE.getConstant(IntTy, Factor);
|
|
if (FactorS->isZero())
|
|
continue;
|
|
// Divide out the factor, ignoring high bits, since we'll be
|
|
// scaling the value back up in the end.
|
|
if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) {
|
|
// TODO: This could be optimized to avoid all the copying.
|
|
Formula F = Base;
|
|
F.ScaledReg = Quotient;
|
|
F.DeleteBaseReg(F.BaseRegs[i]);
|
|
(void)InsertFormula(LU, LUIdx, F);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/// GenerateTruncates - Generate reuse formulae from different IV types.
|
|
void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base) {
|
|
// This requires TargetLowering to tell us which truncates are free.
|
|
if (!TLI) return;
|
|
|
|
// Don't bother truncating symbolic values.
|
|
if (Base.AM.BaseGV) return;
|
|
|
|
// Determine the integer type for the base formula.
|
|
const Type *DstTy = Base.getType();
|
|
if (!DstTy) return;
|
|
DstTy = SE.getEffectiveSCEVType(DstTy);
|
|
|
|
for (SmallSetVector<const Type *, 4>::const_iterator
|
|
I = Types.begin(), E = Types.end(); I != E; ++I) {
|
|
const Type *SrcTy = *I;
|
|
if (SrcTy != DstTy && TLI->isTruncateFree(SrcTy, DstTy)) {
|
|
Formula F = Base;
|
|
|
|
if (F.ScaledReg) F.ScaledReg = SE.getAnyExtendExpr(F.ScaledReg, *I);
|
|
for (SmallVectorImpl<const SCEV *>::iterator J = F.BaseRegs.begin(),
|
|
JE = F.BaseRegs.end(); J != JE; ++J)
|
|
*J = SE.getAnyExtendExpr(*J, SrcTy);
|
|
|
|
// TODO: This assumes we've done basic processing on all uses and
|
|
// have an idea what the register usage is.
|
|
if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses))
|
|
continue;
|
|
|
|
(void)InsertFormula(LU, LUIdx, F);
|
|
}
|
|
}
|
|
}
|
|
|
|
namespace {
|
|
|
|
/// WorkItem - Helper class for GenerateCrossUseConstantOffsets. It's used to
|
|
/// defer modifications so that the search phase doesn't have to worry about
|
|
/// the data structures moving underneath it.
|
|
struct WorkItem {
|
|
size_t LUIdx;
|
|
int64_t Imm;
|
|
const SCEV *OrigReg;
|
|
|
|
WorkItem(size_t LI, int64_t I, const SCEV *R)
|
|
: LUIdx(LI), Imm(I), OrigReg(R) {}
|
|
|
|
void print(raw_ostream &OS) const;
|
|
void dump() const;
|
|
};
|
|
|
|
}
|
|
|
|
void WorkItem::print(raw_ostream &OS) const {
|
|
OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx
|
|
<< " , add offset " << Imm;
|
|
}
|
|
|
|
void WorkItem::dump() const {
|
|
print(errs()); errs() << '\n';
|
|
}
|
|
|
|
/// GenerateCrossUseConstantOffsets - Look for registers which are a constant
|
|
/// distance apart and try to form reuse opportunities between them.
|
|
void LSRInstance::GenerateCrossUseConstantOffsets() {
|
|
// Group the registers by their value without any added constant offset.
|
|
typedef std::map<int64_t, const SCEV *> ImmMapTy;
|
|
typedef DenseMap<const SCEV *, ImmMapTy> RegMapTy;
|
|
RegMapTy Map;
|
|
DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap;
|
|
SmallVector<const SCEV *, 8> Sequence;
|
|
for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end();
|
|
I != E; ++I) {
|
|
const SCEV *Reg = *I;
|
|
int64_t Imm = ExtractImmediate(Reg, SE);
|
|
std::pair<RegMapTy::iterator, bool> Pair =
|
|
Map.insert(std::make_pair(Reg, ImmMapTy()));
|
|
if (Pair.second)
|
|
Sequence.push_back(Reg);
|
|
Pair.first->second.insert(std::make_pair(Imm, *I));
|
|
UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(*I);
|
|
}
|
|
|
|
// Now examine each set of registers with the same base value. Build up
|
|
// a list of work to do and do the work in a separate step so that we're
|
|
// not adding formulae and register counts while we're searching.
|
|
SmallVector<WorkItem, 32> WorkItems;
|
|
SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems;
|
|
for (SmallVectorImpl<const SCEV *>::const_iterator I = Sequence.begin(),
|
|
E = Sequence.end(); I != E; ++I) {
|
|
const SCEV *Reg = *I;
|
|
const ImmMapTy &Imms = Map.find(Reg)->second;
|
|
|
|
// It's not worthwhile looking for reuse if there's only one offset.
|
|
if (Imms.size() == 1)
|
|
continue;
|
|
|
|
DEBUG(dbgs() << "Generating cross-use offsets for " << *Reg << ':';
|
|
for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
|
|
J != JE; ++J)
|
|
dbgs() << ' ' << J->first;
|
|
dbgs() << '\n');
|
|
|
|
// Examine each offset.
|
|
for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
|
|
J != JE; ++J) {
|
|
const SCEV *OrigReg = J->second;
|
|
|
|
int64_t JImm = J->first;
|
|
const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg);
|
|
|
|
if (!isa<SCEVConstant>(OrigReg) &&
|
|
UsedByIndicesMap[Reg].count() == 1) {
|
|
DEBUG(dbgs() << "Skipping cross-use reuse for " << *OrigReg << '\n');
|
|
continue;
|
|
}
|
|
|
|
// Conservatively examine offsets between this orig reg a few selected
|
|
// other orig regs.
|
|
ImmMapTy::const_iterator OtherImms[] = {
|
|
Imms.begin(), prior(Imms.end()),
|
|
Imms.upper_bound((Imms.begin()->first + prior(Imms.end())->first) / 2)
|
|
};
|
|
for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) {
|
|
ImmMapTy::const_iterator M = OtherImms[i];
|
|
if (M == J || M == JE) continue;
|
|
|
|
// Compute the difference between the two.
|
|
int64_t Imm = (uint64_t)JImm - M->first;
|
|
for (int LUIdx = UsedByIndices.find_first(); LUIdx != -1;
|
|
LUIdx = UsedByIndices.find_next(LUIdx))
|
|
// Make a memo of this use, offset, and register tuple.
|
|
if (UniqueItems.insert(std::make_pair(LUIdx, Imm)))
|
|
WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg));
|
|
}
|
|
}
|
|
}
|
|
|
|
Map.clear();
|
|
Sequence.clear();
|
|
UsedByIndicesMap.clear();
|
|
UniqueItems.clear();
|
|
|
|
// Now iterate through the worklist and add new formulae.
|
|
for (SmallVectorImpl<WorkItem>::const_iterator I = WorkItems.begin(),
|
|
E = WorkItems.end(); I != E; ++I) {
|
|
const WorkItem &WI = *I;
|
|
size_t LUIdx = WI.LUIdx;
|
|
LSRUse &LU = Uses[LUIdx];
|
|
int64_t Imm = WI.Imm;
|
|
const SCEV *OrigReg = WI.OrigReg;
|
|
|
|
const Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType());
|
|
const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm));
|
|
unsigned BitWidth = SE.getTypeSizeInBits(IntTy);
|
|
|
|
// TODO: Use a more targeted data structure.
|
|
for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) {
|
|
const Formula &F = LU.Formulae[L];
|
|
// Use the immediate in the scaled register.
|
|
if (F.ScaledReg == OrigReg) {
|
|
int64_t Offs = (uint64_t)F.AM.BaseOffs +
|
|
Imm * (uint64_t)F.AM.Scale;
|
|
// Don't create 50 + reg(-50).
|
|
if (F.referencesReg(SE.getSCEV(
|
|
ConstantInt::get(IntTy, -(uint64_t)Offs))))
|
|
continue;
|
|
Formula NewF = F;
|
|
NewF.AM.BaseOffs = Offs;
|
|
if (!isLegalUse(NewF.AM, LU.MinOffset, LU.MaxOffset,
|
|
LU.Kind, LU.AccessTy, TLI))
|
|
continue;
|
|
NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg);
|
|
|
|
// If the new scale is a constant in a register, and adding the constant
|
|
// value to the immediate would produce a value closer to zero than the
|
|
// immediate itself, then the formula isn't worthwhile.
|
|
if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg))
|
|
if (C->getValue()->getValue().isNegative() !=
|
|
(NewF.AM.BaseOffs < 0) &&
|
|
(C->getValue()->getValue().abs() * APInt(BitWidth, F.AM.Scale))
|
|
.ule(abs64(NewF.AM.BaseOffs)))
|
|
continue;
|
|
|
|
// OK, looks good.
|
|
(void)InsertFormula(LU, LUIdx, NewF);
|
|
} else {
|
|
// Use the immediate in a base register.
|
|
for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) {
|
|
const SCEV *BaseReg = F.BaseRegs[N];
|
|
if (BaseReg != OrigReg)
|
|
continue;
|
|
Formula NewF = F;
|
|
NewF.AM.BaseOffs = (uint64_t)NewF.AM.BaseOffs + Imm;
|
|
if (!isLegalUse(NewF.AM, LU.MinOffset, LU.MaxOffset,
|
|
LU.Kind, LU.AccessTy, TLI))
|
|
continue;
|
|
NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg);
|
|
|
|
// If the new formula has a constant in a register, and adding the
|
|
// constant value to the immediate would produce a value closer to
|
|
// zero than the immediate itself, then the formula isn't worthwhile.
|
|
for (SmallVectorImpl<const SCEV *>::const_iterator
|
|
J = NewF.BaseRegs.begin(), JE = NewF.BaseRegs.end();
|
|
J != JE; ++J)
|
|
if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*J))
|
|
if ((C->getValue()->getValue() + NewF.AM.BaseOffs).abs().slt(
|
|
abs64(NewF.AM.BaseOffs)) &&
|
|
(C->getValue()->getValue() +
|
|
NewF.AM.BaseOffs).countTrailingZeros() >=
|
|
CountTrailingZeros_64(NewF.AM.BaseOffs))
|
|
goto skip_formula;
|
|
|
|
// Ok, looks good.
|
|
(void)InsertFormula(LU, LUIdx, NewF);
|
|
break;
|
|
skip_formula:;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/// GenerateAllReuseFormulae - Generate formulae for each use.
|
|
void
|
|
LSRInstance::GenerateAllReuseFormulae() {
|
|
// This is split into multiple loops so that hasRegsUsedByUsesOtherThan
|
|
// queries are more precise.
|
|
for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
|
|
LSRUse &LU = Uses[LUIdx];
|
|
for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
|
|
GenerateReassociations(LU, LUIdx, LU.Formulae[i]);
|
|
for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
|
|
GenerateCombinations(LU, LUIdx, LU.Formulae[i]);
|
|
}
|
|
for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
|
|
LSRUse &LU = Uses[LUIdx];
|
|
for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
|
|
GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]);
|
|
for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
|
|
GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]);
|
|
for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
|
|
GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]);
|
|
for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
|
|
GenerateScales(LU, LUIdx, LU.Formulae[i]);
|
|
}
|
|
for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
|
|
LSRUse &LU = Uses[LUIdx];
|
|
for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
|
|
GenerateTruncates(LU, LUIdx, LU.Formulae[i]);
|
|
}
|
|
|
|
GenerateCrossUseConstantOffsets();
|
|
}
|
|
|
|
/// If their are multiple formulae with the same set of registers used
|
|
/// by other uses, pick the best one and delete the others.
|
|
void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
|
|
#ifndef NDEBUG
|
|
bool ChangedFormulae = false;
|
|
#endif
|
|
|
|
// Collect the best formula for each unique set of shared registers. This
|
|
// is reset for each use.
|
|
typedef DenseMap<SmallVector<const SCEV *, 2>, size_t, UniquifierDenseMapInfo>
|
|
BestFormulaeTy;
|
|
BestFormulaeTy BestFormulae;
|
|
|
|
for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
|
|
LSRUse &LU = Uses[LUIdx];
|
|
FormulaSorter Sorter(L, LU, SE, DT);
|
|
DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs()); dbgs() << '\n');
|
|
|
|
bool Any = false;
|
|
for (size_t FIdx = 0, NumForms = LU.Formulae.size();
|
|
FIdx != NumForms; ++FIdx) {
|
|
Formula &F = LU.Formulae[FIdx];
|
|
|
|
SmallVector<const SCEV *, 2> Key;
|
|
for (SmallVectorImpl<const SCEV *>::const_iterator J = F.BaseRegs.begin(),
|
|
JE = F.BaseRegs.end(); J != JE; ++J) {
|
|
const SCEV *Reg = *J;
|
|
if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx))
|
|
Key.push_back(Reg);
|
|
}
|
|
if (F.ScaledReg &&
|
|
RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx))
|
|
Key.push_back(F.ScaledReg);
|
|
// Unstable sort by host order ok, because this is only used for
|
|
// uniquifying.
|
|
std::sort(Key.begin(), Key.end());
|
|
|
|
std::pair<BestFormulaeTy::const_iterator, bool> P =
|
|
BestFormulae.insert(std::make_pair(Key, FIdx));
|
|
if (!P.second) {
|
|
Formula &Best = LU.Formulae[P.first->second];
|
|
if (Sorter.operator()(F, Best))
|
|
std::swap(F, Best);
|
|
DEBUG(dbgs() << " Filtering out formula "; F.print(dbgs());
|
|
dbgs() << "\n"
|
|
" in favor of formula "; Best.print(dbgs());
|
|
dbgs() << '\n');
|
|
#ifndef NDEBUG
|
|
ChangedFormulae = true;
|
|
#endif
|
|
LU.DeleteFormula(F);
|
|
--FIdx;
|
|
--NumForms;
|
|
Any = true;
|
|
continue;
|
|
}
|
|
}
|
|
|
|
// Now that we've filtered out some formulae, recompute the Regs set.
|
|
if (Any)
|
|
LU.RecomputeRegs(LUIdx, RegUses);
|
|
|
|
// Reset this to prepare for the next use.
|
|
BestFormulae.clear();
|
|
}
|
|
|
|
DEBUG(if (ChangedFormulae) {
|
|
dbgs() << "\n"
|
|
"After filtering out undesirable candidates:\n";
|
|
print_uses(dbgs());
|
|
});
|
|
}
|
|
|
|
// This is a rough guess that seems to work fairly well.
|
|
static const size_t ComplexityLimit = UINT16_MAX;
|
|
|
|
/// EstimateSearchSpaceComplexity - Estimate the worst-case number of
|
|
/// solutions the solver might have to consider. It almost never considers
|
|
/// this many solutions because it prune the search space, but the pruning
|
|
/// isn't always sufficient.
|
|
size_t LSRInstance::EstimateSearchSpaceComplexity() const {
|
|
uint32_t Power = 1;
|
|
for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
|
|
E = Uses.end(); I != E; ++I) {
|
|
size_t FSize = I->Formulae.size();
|
|
if (FSize >= ComplexityLimit) {
|
|
Power = ComplexityLimit;
|
|
break;
|
|
}
|
|
Power *= FSize;
|
|
if (Power >= ComplexityLimit)
|
|
break;
|
|
}
|
|
return Power;
|
|
}
|
|
|
|
/// NarrowSearchSpaceUsingHeuristics - If there are an extraordinary number of
|
|
/// formulae to choose from, use some rough heuristics to prune down the number
|
|
/// of formulae. This keeps the main solver from taking an extraordinary amount
|
|
/// of time in some worst-case scenarios.
|
|
void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
|
|
if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
|
|
DEBUG(dbgs() << "The search space is too complex.\n");
|
|
|
|
DEBUG(dbgs() << "Narrowing the search space by eliminating formulae "
|
|
"which use a superset of registers used by other "
|
|
"formulae.\n");
|
|
|
|
for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
|
|
LSRUse &LU = Uses[LUIdx];
|
|
bool Any = false;
|
|
for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
|
|
Formula &F = LU.Formulae[i];
|
|
// Look for a formula with a constant or GV in a register. If the use
|
|
// also has a formula with that same value in an immediate field,
|
|
// delete the one that uses a register.
|
|
for (SmallVectorImpl<const SCEV *>::const_iterator
|
|
I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) {
|
|
if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) {
|
|
Formula NewF = F;
|
|
NewF.AM.BaseOffs += C->getValue()->getSExtValue();
|
|
NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
|
|
(I - F.BaseRegs.begin()));
|
|
if (LU.HasFormulaWithSameRegs(NewF)) {
|
|
DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
|
|
LU.DeleteFormula(F);
|
|
--i;
|
|
--e;
|
|
Any = true;
|
|
break;
|
|
}
|
|
} else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(*I)) {
|
|
if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue()))
|
|
if (!F.AM.BaseGV) {
|
|
Formula NewF = F;
|
|
NewF.AM.BaseGV = GV;
|
|
NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
|
|
(I - F.BaseRegs.begin()));
|
|
if (LU.HasFormulaWithSameRegs(NewF)) {
|
|
DEBUG(dbgs() << " Deleting "; F.print(dbgs());
|
|
dbgs() << '\n');
|
|
LU.DeleteFormula(F);
|
|
--i;
|
|
--e;
|
|
Any = true;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
if (Any)
|
|
LU.RecomputeRegs(LUIdx, RegUses);
|
|
}
|
|
|
|
DEBUG(dbgs() << "After pre-selection:\n";
|
|
print_uses(dbgs()));
|
|
}
|
|
|
|
if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
|
|
DEBUG(dbgs() << "The search space is too complex.\n");
|
|
|
|
DEBUG(dbgs() << "Narrowing the search space by assuming that uses "
|
|
"separated by a constant offset will use the same "
|
|
"registers.\n");
|
|
|
|
// This is especially useful for unrolled loops.
|
|
|
|
for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
|
|
LSRUse &LU = Uses[LUIdx];
|
|
for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
|
|
E = LU.Formulae.end(); I != E; ++I) {
|
|
const Formula &F = *I;
|
|
if (F.AM.BaseOffs != 0 && F.AM.Scale == 0) {
|
|
if (LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU)) {
|
|
if (reconcileNewOffset(*LUThatHas, F.AM.BaseOffs,
|
|
/*HasBaseReg=*/false,
|
|
LU.Kind, LU.AccessTy)) {
|
|
DEBUG(dbgs() << " Deleting use "; LU.print(dbgs());
|
|
dbgs() << '\n');
|
|
|
|
LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop;
|
|
|
|
// Delete formulae from the new use which are no longer legal.
|
|
bool Any = false;
|
|
for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) {
|
|
Formula &F = LUThatHas->Formulae[i];
|
|
if (!isLegalUse(F.AM,
|
|
LUThatHas->MinOffset, LUThatHas->MaxOffset,
|
|
LUThatHas->Kind, LUThatHas->AccessTy, TLI)) {
|
|
DEBUG(dbgs() << " Deleting "; F.print(dbgs());
|
|
dbgs() << '\n');
|
|
LUThatHas->DeleteFormula(F);
|
|
--i;
|
|
--e;
|
|
Any = true;
|
|
}
|
|
}
|
|
if (Any)
|
|
LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses);
|
|
|
|
// Update the relocs to reference the new use.
|
|
for (SmallVectorImpl<LSRFixup>::iterator I = Fixups.begin(),
|
|
E = Fixups.end(); I != E; ++I) {
|
|
LSRFixup &Fixup = *I;
|
|
if (Fixup.LUIdx == LUIdx) {
|
|
Fixup.LUIdx = LUThatHas - &Uses.front();
|
|
Fixup.Offset += F.AM.BaseOffs;
|
|
DEBUG(errs() << "New fixup has offset "
|
|
<< Fixup.Offset << '\n');
|
|
}
|
|
if (Fixup.LUIdx == NumUses-1)
|
|
Fixup.LUIdx = LUIdx;
|
|
}
|
|
|
|
// Delete the old use.
|
|
DeleteUse(LU);
|
|
--LUIdx;
|
|
--NumUses;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
DEBUG(dbgs() << "After pre-selection:\n";
|
|
print_uses(dbgs()));
|
|
}
|
|
|
|
// With all other options exhausted, loop until the system is simple
|
|
// enough to handle.
|
|
SmallPtrSet<const SCEV *, 4> Taken;
|
|
while (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
|
|
// Ok, we have too many of formulae on our hands to conveniently handle.
|
|
// Use a rough heuristic to thin out the list.
|
|
DEBUG(dbgs() << "The search space is too complex.\n");
|
|
|
|
// Pick the register which is used by the most LSRUses, which is likely
|
|
// to be a good reuse register candidate.
|
|
const SCEV *Best = 0;
|
|
unsigned BestNum = 0;
|
|
for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end();
|
|
I != E; ++I) {
|
|
const SCEV *Reg = *I;
|
|
if (Taken.count(Reg))
|
|
continue;
|
|
if (!Best)
|
|
Best = Reg;
|
|
else {
|
|
unsigned Count = RegUses.getUsedByIndices(Reg).count();
|
|
if (Count > BestNum) {
|
|
Best = Reg;
|
|
BestNum = Count;
|
|
}
|
|
}
|
|
}
|
|
|
|
DEBUG(dbgs() << "Narrowing the search space by assuming " << *Best
|
|
<< " will yield profitable reuse.\n");
|
|
Taken.insert(Best);
|
|
|
|
// In any use with formulae which references this register, delete formulae
|
|
// which don't reference it.
|
|
for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
|
|
LSRUse &LU = Uses[LUIdx];
|
|
if (!LU.Regs.count(Best)) continue;
|
|
|
|
bool Any = false;
|
|
for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
|
|
Formula &F = LU.Formulae[i];
|
|
if (!F.referencesReg(Best)) {
|
|
DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
|
|
LU.DeleteFormula(F);
|
|
--e;
|
|
--i;
|
|
Any = true;
|
|
assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?");
|
|
continue;
|
|
}
|
|
}
|
|
|
|
if (Any)
|
|
LU.RecomputeRegs(LUIdx, RegUses);
|
|
}
|
|
|
|
DEBUG(dbgs() << "After pre-selection:\n";
|
|
print_uses(dbgs()));
|
|
}
|
|
}
|
|
|
|
/// SolveRecurse - This is the recursive solver.
|
|
void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
|
|
Cost &SolutionCost,
|
|
SmallVectorImpl<const Formula *> &Workspace,
|
|
const Cost &CurCost,
|
|
const SmallPtrSet<const SCEV *, 16> &CurRegs,
|
|
DenseSet<const SCEV *> &VisitedRegs) const {
|
|
// Some ideas:
|
|
// - prune more:
|
|
// - use more aggressive filtering
|
|
// - sort the formula so that the most profitable solutions are found first
|
|
// - sort the uses too
|
|
// - search faster:
|
|
// - don't compute a cost, and then compare. compare while computing a cost
|
|
// and bail early.
|
|
// - track register sets with SmallBitVector
|
|
|
|
const LSRUse &LU = Uses[Workspace.size()];
|
|
|
|
// If this use references any register that's already a part of the
|
|
// in-progress solution, consider it a requirement that a formula must
|
|
// reference that register in order to be considered. This prunes out
|
|
// unprofitable searching.
|
|
SmallSetVector<const SCEV *, 4> ReqRegs;
|
|
for (SmallPtrSet<const SCEV *, 16>::const_iterator I = CurRegs.begin(),
|
|
E = CurRegs.end(); I != E; ++I)
|
|
if (LU.Regs.count(*I))
|
|
ReqRegs.insert(*I);
|
|
|
|
bool AnySatisfiedReqRegs = false;
|
|
SmallPtrSet<const SCEV *, 16> NewRegs;
|
|
Cost NewCost;
|
|
retry:
|
|
for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
|
|
E = LU.Formulae.end(); I != E; ++I) {
|
|
const Formula &F = *I;
|
|
|
|
// Ignore formulae which do not use any of the required registers.
|
|
for (SmallSetVector<const SCEV *, 4>::const_iterator J = ReqRegs.begin(),
|
|
JE = ReqRegs.end(); J != JE; ++J) {
|
|
const SCEV *Reg = *J;
|
|
if ((!F.ScaledReg || F.ScaledReg != Reg) &&
|
|
std::find(F.BaseRegs.begin(), F.BaseRegs.end(), Reg) ==
|
|
F.BaseRegs.end())
|
|
goto skip;
|
|
}
|
|
AnySatisfiedReqRegs = true;
|
|
|
|
// Evaluate the cost of the current formula. If it's already worse than
|
|
// the current best, prune the search at that point.
|
|
NewCost = CurCost;
|
|
NewRegs = CurRegs;
|
|
NewCost.RateFormula(F, NewRegs, VisitedRegs, L, LU.Offsets, SE, DT);
|
|
if (NewCost < SolutionCost) {
|
|
Workspace.push_back(&F);
|
|
if (Workspace.size() != Uses.size()) {
|
|
SolveRecurse(Solution, SolutionCost, Workspace, NewCost,
|
|
NewRegs, VisitedRegs);
|
|
if (F.getNumRegs() == 1 && Workspace.size() == 1)
|
|
VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]);
|
|
} else {
|
|
DEBUG(dbgs() << "New best at "; NewCost.print(dbgs());
|
|
dbgs() << ". Regs:";
|
|
for (SmallPtrSet<const SCEV *, 16>::const_iterator
|
|
I = NewRegs.begin(), E = NewRegs.end(); I != E; ++I)
|
|
dbgs() << ' ' << **I;
|
|
dbgs() << '\n');
|
|
|
|
SolutionCost = NewCost;
|
|
Solution = Workspace;
|
|
}
|
|
Workspace.pop_back();
|
|
}
|
|
skip:;
|
|
}
|
|
|
|
// If none of the formulae had all of the required registers, relax the
|
|
// constraint so that we don't exclude all formulae.
|
|
if (!AnySatisfiedReqRegs) {
|
|
assert(!ReqRegs.empty() && "Solver failed even without required registers");
|
|
ReqRegs.clear();
|
|
goto retry;
|
|
}
|
|
}
|
|
|
|
/// Solve - Choose one formula from each use. Return the results in the given
|
|
/// Solution vector.
|
|
void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const {
|
|
SmallVector<const Formula *, 8> Workspace;
|
|
Cost SolutionCost;
|
|
SolutionCost.Loose();
|
|
Cost CurCost;
|
|
SmallPtrSet<const SCEV *, 16> CurRegs;
|
|
DenseSet<const SCEV *> VisitedRegs;
|
|
Workspace.reserve(Uses.size());
|
|
|
|
// SolveRecurse does all the work.
|
|
SolveRecurse(Solution, SolutionCost, Workspace, CurCost,
|
|
CurRegs, VisitedRegs);
|
|
|
|
// Ok, we've now made all our decisions.
|
|
DEBUG(dbgs() << "\n"
|
|
"The chosen solution requires "; SolutionCost.print(dbgs());
|
|
dbgs() << ":\n";
|
|
for (size_t i = 0, e = Uses.size(); i != e; ++i) {
|
|
dbgs() << " ";
|
|
Uses[i].print(dbgs());
|
|
dbgs() << "\n"
|
|
" ";
|
|
Solution[i]->print(dbgs());
|
|
dbgs() << '\n';
|
|
});
|
|
|
|
assert(Solution.size() == Uses.size() && "Malformed solution!");
|
|
}
|
|
|
|
/// HoistInsertPosition - Helper for AdjustInsertPositionForExpand. Climb up
|
|
/// the dominator tree far as we can go while still being dominated by the
|
|
/// input positions. This helps canonicalize the insert position, which
|
|
/// encourages sharing.
|
|
BasicBlock::iterator
|
|
LSRInstance::HoistInsertPosition(BasicBlock::iterator IP,
|
|
const SmallVectorImpl<Instruction *> &Inputs)
|
|
const {
|
|
for (;;) {
|
|
const Loop *IPLoop = LI.getLoopFor(IP->getParent());
|
|
unsigned IPLoopDepth = IPLoop ? IPLoop->getLoopDepth() : 0;
|
|
|
|
BasicBlock *IDom;
|
|
for (DomTreeNode *Rung = DT.getNode(IP->getParent()); ; ) {
|
|
if (!Rung) return IP;
|
|
Rung = Rung->getIDom();
|
|
if (!Rung) return IP;
|
|
IDom = Rung->getBlock();
|
|
|
|
// Don't climb into a loop though.
|
|
const Loop *IDomLoop = LI.getLoopFor(IDom);
|
|
unsigned IDomDepth = IDomLoop ? IDomLoop->getLoopDepth() : 0;
|
|
if (IDomDepth <= IPLoopDepth &&
|
|
(IDomDepth != IPLoopDepth || IDomLoop == IPLoop))
|
|
break;
|
|
}
|
|
|
|
bool AllDominate = true;
|
|
Instruction *BetterPos = 0;
|
|
Instruction *Tentative = IDom->getTerminator();
|
|
for (SmallVectorImpl<Instruction *>::const_iterator I = Inputs.begin(),
|
|
E = Inputs.end(); I != E; ++I) {
|
|
Instruction *Inst = *I;
|
|
if (Inst == Tentative || !DT.dominates(Inst, Tentative)) {
|
|
AllDominate = false;
|
|
break;
|
|
}
|
|
// Attempt to find an insert position in the middle of the block,
|
|
// instead of at the end, so that it can be used for other expansions.
|
|
if (IDom == Inst->getParent() &&
|
|
(!BetterPos || DT.dominates(BetterPos, Inst)))
|
|
BetterPos = llvm::next(BasicBlock::iterator(Inst));
|
|
}
|
|
if (!AllDominate)
|
|
break;
|
|
if (BetterPos)
|
|
IP = BetterPos;
|
|
else
|
|
IP = Tentative;
|
|
}
|
|
|
|
return IP;
|
|
}
|
|
|
|
/// AdjustInsertPositionForExpand - Determine an input position which will be
|
|
/// dominated by the operands and which will dominate the result.
|
|
BasicBlock::iterator
|
|
LSRInstance::AdjustInsertPositionForExpand(BasicBlock::iterator IP,
|
|
const LSRFixup &LF,
|
|
const LSRUse &LU) const {
|
|
// Collect some instructions which must be dominated by the
|
|
// expanding replacement. These must be dominated by any operands that
|
|
// will be required in the expansion.
|
|
SmallVector<Instruction *, 4> Inputs;
|
|
if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace))
|
|
Inputs.push_back(I);
|
|
if (LU.Kind == LSRUse::ICmpZero)
|
|
if (Instruction *I =
|
|
dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1)))
|
|
Inputs.push_back(I);
|
|
if (LF.PostIncLoops.count(L)) {
|
|
if (LF.isUseFullyOutsideLoop(L))
|
|
Inputs.push_back(L->getLoopLatch()->getTerminator());
|
|
else
|
|
Inputs.push_back(IVIncInsertPos);
|
|
}
|
|
// The expansion must also be dominated by the increment positions of any
|
|
// loops it for which it is using post-inc mode.
|
|
for (PostIncLoopSet::const_iterator I = LF.PostIncLoops.begin(),
|
|
E = LF.PostIncLoops.end(); I != E; ++I) {
|
|
const Loop *PIL = *I;
|
|
if (PIL == L) continue;
|
|
|
|
// Be dominated by the loop exit.
|
|
SmallVector<BasicBlock *, 4> ExitingBlocks;
|
|
PIL->getExitingBlocks(ExitingBlocks);
|
|
if (!ExitingBlocks.empty()) {
|
|
BasicBlock *BB = ExitingBlocks[0];
|
|
for (unsigned i = 1, e = ExitingBlocks.size(); i != e; ++i)
|
|
BB = DT.findNearestCommonDominator(BB, ExitingBlocks[i]);
|
|
Inputs.push_back(BB->getTerminator());
|
|
}
|
|
}
|
|
|
|
// Then, climb up the immediate dominator tree as far as we can go while
|
|
// still being dominated by the input positions.
|
|
IP = HoistInsertPosition(IP, Inputs);
|
|
|
|
// Don't insert instructions before PHI nodes.
|
|
while (isa<PHINode>(IP)) ++IP;
|
|
|
|
// Ignore debug intrinsics.
|
|
while (isa<DbgInfoIntrinsic>(IP)) ++IP;
|
|
|
|
return IP;
|
|
}
|
|
|
|
/// Expand - Emit instructions for the leading candidate expression for this
|
|
/// LSRUse (this is called "expanding").
|
|
Value *LSRInstance::Expand(const LSRFixup &LF,
|
|
const Formula &F,
|
|
BasicBlock::iterator IP,
|
|
SCEVExpander &Rewriter,
|
|
SmallVectorImpl<WeakVH> &DeadInsts) const {
|
|
const LSRUse &LU = Uses[LF.LUIdx];
|
|
|
|
// Determine an input position which will be dominated by the operands and
|
|
// which will dominate the result.
|
|
IP = AdjustInsertPositionForExpand(IP, LF, LU);
|
|
|
|
// Inform the Rewriter if we have a post-increment use, so that it can
|
|
// perform an advantageous expansion.
|
|
Rewriter.setPostInc(LF.PostIncLoops);
|
|
|
|
// This is the type that the user actually needs.
|
|
const Type *OpTy = LF.OperandValToReplace->getType();
|
|
// This will be the type that we'll initially expand to.
|
|
const Type *Ty = F.getType();
|
|
if (!Ty)
|
|
// No type known; just expand directly to the ultimate type.
|
|
Ty = OpTy;
|
|
else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy))
|
|
// Expand directly to the ultimate type if it's the right size.
|
|
Ty = OpTy;
|
|
// This is the type to do integer arithmetic in.
|
|
const Type *IntTy = SE.getEffectiveSCEVType(Ty);
|
|
|
|
// Build up a list of operands to add together to form the full base.
|
|
SmallVector<const SCEV *, 8> Ops;
|
|
|
|
// Expand the BaseRegs portion.
|
|
for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
|
|
E = F.BaseRegs.end(); I != E; ++I) {
|
|
const SCEV *Reg = *I;
|
|
assert(!Reg->isZero() && "Zero allocated in a base register!");
|
|
|
|
// If we're expanding for a post-inc user, make the post-inc adjustment.
|
|
PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
|
|
Reg = TransformForPostIncUse(Denormalize, Reg,
|
|
LF.UserInst, LF.OperandValToReplace,
|
|
Loops, SE, DT);
|
|
|
|
Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, 0, IP)));
|
|
}
|
|
|
|
// Flush the operand list to suppress SCEVExpander hoisting.
|
|
if (!Ops.empty()) {
|
|
Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
|
|
Ops.clear();
|
|
Ops.push_back(SE.getUnknown(FullV));
|
|
}
|
|
|
|
// Expand the ScaledReg portion.
|
|
Value *ICmpScaledV = 0;
|
|
if (F.AM.Scale != 0) {
|
|
const SCEV *ScaledS = F.ScaledReg;
|
|
|
|
// If we're expanding for a post-inc user, make the post-inc adjustment.
|
|
PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
|
|
ScaledS = TransformForPostIncUse(Denormalize, ScaledS,
|
|
LF.UserInst, LF.OperandValToReplace,
|
|
Loops, SE, DT);
|
|
|
|
if (LU.Kind == LSRUse::ICmpZero) {
|
|
// An interesting way of "folding" with an icmp is to use a negated
|
|
// scale, which we'll implement by inserting it into the other operand
|
|
// of the icmp.
|
|
assert(F.AM.Scale == -1 &&
|
|
"The only scale supported by ICmpZero uses is -1!");
|
|
ICmpScaledV = Rewriter.expandCodeFor(ScaledS, 0, IP);
|
|
} else {
|
|
// Otherwise just expand the scaled register and an explicit scale,
|
|
// which is expected to be matched as part of the address.
|
|
ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, 0, IP));
|
|
ScaledS = SE.getMulExpr(ScaledS,
|
|
SE.getConstant(ScaledS->getType(), F.AM.Scale));
|
|
Ops.push_back(ScaledS);
|
|
|
|
// Flush the operand list to suppress SCEVExpander hoisting.
|
|
Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
|
|
Ops.clear();
|
|
Ops.push_back(SE.getUnknown(FullV));
|
|
}
|
|
}
|
|
|
|
// Expand the GV portion.
|
|
if (F.AM.BaseGV) {
|
|
Ops.push_back(SE.getUnknown(F.AM.BaseGV));
|
|
|
|
// Flush the operand list to suppress SCEVExpander hoisting.
|
|
Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
|
|
Ops.clear();
|
|
Ops.push_back(SE.getUnknown(FullV));
|
|
}
|
|
|
|
// Expand the immediate portion.
|
|
int64_t Offset = (uint64_t)F.AM.BaseOffs + LF.Offset;
|
|
if (Offset != 0) {
|
|
if (LU.Kind == LSRUse::ICmpZero) {
|
|
// The other interesting way of "folding" with an ICmpZero is to use a
|
|
// negated immediate.
|
|
if (!ICmpScaledV)
|
|
ICmpScaledV = ConstantInt::get(IntTy, -Offset);
|
|
else {
|
|
Ops.push_back(SE.getUnknown(ICmpScaledV));
|
|
ICmpScaledV = ConstantInt::get(IntTy, Offset);
|
|
}
|
|
} else {
|
|
// Just add the immediate values. These again are expected to be matched
|
|
// as part of the address.
|
|
Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, Offset)));
|
|
}
|
|
}
|
|
|
|
// Emit instructions summing all the operands.
|
|
const SCEV *FullS = Ops.empty() ?
|
|
SE.getConstant(IntTy, 0) :
|
|
SE.getAddExpr(Ops);
|
|
Value *FullV = Rewriter.expandCodeFor(FullS, Ty, IP);
|
|
|
|
// We're done expanding now, so reset the rewriter.
|
|
Rewriter.clearPostInc();
|
|
|
|
// An ICmpZero Formula represents an ICmp which we're handling as a
|
|
// comparison against zero. Now that we've expanded an expression for that
|
|
// form, update the ICmp's other operand.
|
|
if (LU.Kind == LSRUse::ICmpZero) {
|
|
ICmpInst *CI = cast<ICmpInst>(LF.UserInst);
|
|
DeadInsts.push_back(CI->getOperand(1));
|
|
assert(!F.AM.BaseGV && "ICmp does not support folding a global value and "
|
|
"a scale at the same time!");
|
|
if (F.AM.Scale == -1) {
|
|
if (ICmpScaledV->getType() != OpTy) {
|
|
Instruction *Cast =
|
|
CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false,
|
|
OpTy, false),
|
|
ICmpScaledV, OpTy, "tmp", CI);
|
|
ICmpScaledV = Cast;
|
|
}
|
|
CI->setOperand(1, ICmpScaledV);
|
|
} else {
|
|
assert(F.AM.Scale == 0 &&
|
|
"ICmp does not support folding a global value and "
|
|
"a scale at the same time!");
|
|
Constant *C = ConstantInt::getSigned(SE.getEffectiveSCEVType(OpTy),
|
|
-(uint64_t)Offset);
|
|
if (C->getType() != OpTy)
|
|
C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
|
|
OpTy, false),
|
|
C, OpTy);
|
|
|
|
CI->setOperand(1, C);
|
|
}
|
|
}
|
|
|
|
return FullV;
|
|
}
|
|
|
|
/// RewriteForPHI - Helper for Rewrite. PHI nodes are special because the use
|
|
/// of their operands effectively happens in their predecessor blocks, so the
|
|
/// expression may need to be expanded in multiple places.
|
|
void LSRInstance::RewriteForPHI(PHINode *PN,
|
|
const LSRFixup &LF,
|
|
const Formula &F,
|
|
SCEVExpander &Rewriter,
|
|
SmallVectorImpl<WeakVH> &DeadInsts,
|
|
Pass *P) const {
|
|
DenseMap<BasicBlock *, Value *> Inserted;
|
|
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
|
|
if (PN->getIncomingValue(i) == LF.OperandValToReplace) {
|
|
BasicBlock *BB = PN->getIncomingBlock(i);
|
|
|
|
// If this is a critical edge, split the edge so that we do not insert
|
|
// the code on all predecessor/successor paths. We do this unless this
|
|
// is the canonical backedge for this loop, which complicates post-inc
|
|
// users.
|
|
if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 &&
|
|
!isa<IndirectBrInst>(BB->getTerminator()) &&
|
|
(PN->getParent() != L->getHeader() || !L->contains(BB))) {
|
|
// Split the critical edge.
|
|
BasicBlock *NewBB = SplitCriticalEdge(BB, PN->getParent(), P);
|
|
|
|
// If PN is outside of the loop and BB is in the loop, we want to
|
|
// move the block to be immediately before the PHI block, not
|
|
// immediately after BB.
|
|
if (L->contains(BB) && !L->contains(PN))
|
|
NewBB->moveBefore(PN->getParent());
|
|
|
|
// Splitting the edge can reduce the number of PHI entries we have.
|
|
e = PN->getNumIncomingValues();
|
|
BB = NewBB;
|
|
i = PN->getBasicBlockIndex(BB);
|
|
}
|
|
|
|
std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair =
|
|
Inserted.insert(std::make_pair(BB, static_cast<Value *>(0)));
|
|
if (!Pair.second)
|
|
PN->setIncomingValue(i, Pair.first->second);
|
|
else {
|
|
Value *FullV = Expand(LF, F, BB->getTerminator(), Rewriter, DeadInsts);
|
|
|
|
// If this is reuse-by-noop-cast, insert the noop cast.
|
|
const Type *OpTy = LF.OperandValToReplace->getType();
|
|
if (FullV->getType() != OpTy)
|
|
FullV =
|
|
CastInst::Create(CastInst::getCastOpcode(FullV, false,
|
|
OpTy, false),
|
|
FullV, LF.OperandValToReplace->getType(),
|
|
"tmp", BB->getTerminator());
|
|
|
|
PN->setIncomingValue(i, FullV);
|
|
Pair.first->second = FullV;
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Rewrite - Emit instructions for the leading candidate expression for this
|
|
/// LSRUse (this is called "expanding"), and update the UserInst to reference
|
|
/// the newly expanded value.
|
|
void LSRInstance::Rewrite(const LSRFixup &LF,
|
|
const Formula &F,
|
|
SCEVExpander &Rewriter,
|
|
SmallVectorImpl<WeakVH> &DeadInsts,
|
|
Pass *P) const {
|
|
// First, find an insertion point that dominates UserInst. For PHI nodes,
|
|
// find the nearest block which dominates all the relevant uses.
|
|
if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) {
|
|
RewriteForPHI(PN, LF, F, Rewriter, DeadInsts, P);
|
|
} else {
|
|
Value *FullV = Expand(LF, F, LF.UserInst, Rewriter, DeadInsts);
|
|
|
|
// If this is reuse-by-noop-cast, insert the noop cast.
|
|
const Type *OpTy = LF.OperandValToReplace->getType();
|
|
if (FullV->getType() != OpTy) {
|
|
Instruction *Cast =
|
|
CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false),
|
|
FullV, OpTy, "tmp", LF.UserInst);
|
|
FullV = Cast;
|
|
}
|
|
|
|
// Update the user. ICmpZero is handled specially here (for now) because
|
|
// Expand may have updated one of the operands of the icmp already, and
|
|
// its new value may happen to be equal to LF.OperandValToReplace, in
|
|
// which case doing replaceUsesOfWith leads to replacing both operands
|
|
// with the same value. TODO: Reorganize this.
|
|
if (Uses[LF.LUIdx].Kind == LSRUse::ICmpZero)
|
|
LF.UserInst->setOperand(0, FullV);
|
|
else
|
|
LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV);
|
|
}
|
|
|
|
DeadInsts.push_back(LF.OperandValToReplace);
|
|
}
|
|
|
|
/// ImplementSolution - Rewrite all the fixup locations with new values,
|
|
/// following the chosen solution.
|
|
void
|
|
LSRInstance::ImplementSolution(const SmallVectorImpl<const Formula *> &Solution,
|
|
Pass *P) {
|
|
// Keep track of instructions we may have made dead, so that
|
|
// we can remove them after we are done working.
|
|
SmallVector<WeakVH, 16> DeadInsts;
|
|
|
|
SCEVExpander Rewriter(SE);
|
|
Rewriter.disableCanonicalMode();
|
|
Rewriter.setIVIncInsertPos(L, IVIncInsertPos);
|
|
|
|
// Expand the new value definitions and update the users.
|
|
for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(),
|
|
E = Fixups.end(); I != E; ++I) {
|
|
const LSRFixup &Fixup = *I;
|
|
|
|
Rewrite(Fixup, *Solution[Fixup.LUIdx], Rewriter, DeadInsts, P);
|
|
|
|
Changed = true;
|
|
}
|
|
|
|
// Clean up after ourselves. This must be done before deleting any
|
|
// instructions.
|
|
Rewriter.clear();
|
|
|
|
Changed |= DeleteTriviallyDeadInstructions(DeadInsts);
|
|
}
|
|
|
|
LSRInstance::LSRInstance(const TargetLowering *tli, Loop *l, Pass *P)
|
|
: IU(P->getAnalysis<IVUsers>()),
|
|
SE(P->getAnalysis<ScalarEvolution>()),
|
|
DT(P->getAnalysis<DominatorTree>()),
|
|
LI(P->getAnalysis<LoopInfo>()),
|
|
TLI(tli), L(l), Changed(false), IVIncInsertPos(0) {
|
|
|
|
// If LoopSimplify form is not available, stay out of trouble.
|
|
if (!L->isLoopSimplifyForm()) return;
|
|
|
|
// If there's no interesting work to be done, bail early.
|
|
if (IU.empty()) return;
|
|
|
|
DEBUG(dbgs() << "\nLSR on loop ";
|
|
WriteAsOperand(dbgs(), L->getHeader(), /*PrintType=*/false);
|
|
dbgs() << ":\n");
|
|
|
|
// First, perform some low-level loop optimizations.
|
|
OptimizeShadowIV();
|
|
OptimizeLoopTermCond();
|
|
|
|
// Start collecting data and preparing for the solver.
|
|
CollectInterestingTypesAndFactors();
|
|
CollectFixupsAndInitialFormulae();
|
|
CollectLoopInvariantFixupsAndFormulae();
|
|
|
|
DEBUG(dbgs() << "LSR found " << Uses.size() << " uses:\n";
|
|
print_uses(dbgs()));
|
|
|
|
// Now use the reuse data to generate a bunch of interesting ways
|
|
// to formulate the values needed for the uses.
|
|
GenerateAllReuseFormulae();
|
|
|
|
DEBUG(dbgs() << "\n"
|
|
"After generating reuse formulae:\n";
|
|
print_uses(dbgs()));
|
|
|
|
FilterOutUndesirableDedicatedRegisters();
|
|
NarrowSearchSpaceUsingHeuristics();
|
|
|
|
SmallVector<const Formula *, 8> Solution;
|
|
Solve(Solution);
|
|
|
|
// Release memory that is no longer needed.
|
|
Factors.clear();
|
|
Types.clear();
|
|
RegUses.clear();
|
|
|
|
#ifndef NDEBUG
|
|
// Formulae should be legal.
|
|
for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
|
|
E = Uses.end(); I != E; ++I) {
|
|
const LSRUse &LU = *I;
|
|
for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(),
|
|
JE = LU.Formulae.end(); J != JE; ++J)
|
|
assert(isLegalUse(J->AM, LU.MinOffset, LU.MaxOffset,
|
|
LU.Kind, LU.AccessTy, TLI) &&
|
|
"Illegal formula generated!");
|
|
};
|
|
#endif
|
|
|
|
// Now that we've decided what we want, make it so.
|
|
ImplementSolution(Solution, P);
|
|
}
|
|
|
|
void LSRInstance::print_factors_and_types(raw_ostream &OS) const {
|
|
if (Factors.empty() && Types.empty()) return;
|
|
|
|
OS << "LSR has identified the following interesting factors and types: ";
|
|
bool First = true;
|
|
|
|
for (SmallSetVector<int64_t, 8>::const_iterator
|
|
I = Factors.begin(), E = Factors.end(); I != E; ++I) {
|
|
if (!First) OS << ", ";
|
|
First = false;
|
|
OS << '*' << *I;
|
|
}
|
|
|
|
for (SmallSetVector<const Type *, 4>::const_iterator
|
|
I = Types.begin(), E = Types.end(); I != E; ++I) {
|
|
if (!First) OS << ", ";
|
|
First = false;
|
|
OS << '(' << **I << ')';
|
|
}
|
|
OS << '\n';
|
|
}
|
|
|
|
void LSRInstance::print_fixups(raw_ostream &OS) const {
|
|
OS << "LSR is examining the following fixup sites:\n";
|
|
for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(),
|
|
E = Fixups.end(); I != E; ++I) {
|
|
dbgs() << " ";
|
|
I->print(OS);
|
|
OS << '\n';
|
|
}
|
|
}
|
|
|
|
void LSRInstance::print_uses(raw_ostream &OS) const {
|
|
OS << "LSR is examining the following uses:\n";
|
|
for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
|
|
E = Uses.end(); I != E; ++I) {
|
|
const LSRUse &LU = *I;
|
|
dbgs() << " ";
|
|
LU.print(OS);
|
|
OS << '\n';
|
|
for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(),
|
|
JE = LU.Formulae.end(); J != JE; ++J) {
|
|
OS << " ";
|
|
J->print(OS);
|
|
OS << '\n';
|
|
}
|
|
}
|
|
}
|
|
|
|
void LSRInstance::print(raw_ostream &OS) const {
|
|
print_factors_and_types(OS);
|
|
print_fixups(OS);
|
|
print_uses(OS);
|
|
}
|
|
|
|
void LSRInstance::dump() const {
|
|
print(errs()); errs() << '\n';
|
|
}
|
|
|
|
namespace {
|
|
|
|
class LoopStrengthReduce : public LoopPass {
|
|
/// TLI - Keep a pointer of a TargetLowering to consult for determining
|
|
/// transformation profitability.
|
|
const TargetLowering *const TLI;
|
|
|
|
public:
|
|
static char ID; // Pass ID, replacement for typeid
|
|
explicit LoopStrengthReduce(const TargetLowering *tli = 0);
|
|
|
|
private:
|
|
bool runOnLoop(Loop *L, LPPassManager &LPM);
|
|
void getAnalysisUsage(AnalysisUsage &AU) const;
|
|
};
|
|
|
|
}
|
|
|
|
char LoopStrengthReduce::ID = 0;
|
|
static RegisterPass<LoopStrengthReduce>
|
|
X("loop-reduce", "Loop Strength Reduction");
|
|
|
|
Pass *llvm::createLoopStrengthReducePass(const TargetLowering *TLI) {
|
|
return new LoopStrengthReduce(TLI);
|
|
}
|
|
|
|
LoopStrengthReduce::LoopStrengthReduce(const TargetLowering *tli)
|
|
: LoopPass(&ID), TLI(tli) {}
|
|
|
|
void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const {
|
|
// We split critical edges, so we change the CFG. However, we do update
|
|
// many analyses if they are around.
|
|
AU.addPreservedID(LoopSimplifyID);
|
|
AU.addPreserved("domfrontier");
|
|
|
|
AU.addRequired<LoopInfo>();
|
|
AU.addPreserved<LoopInfo>();
|
|
AU.addRequiredID(LoopSimplifyID);
|
|
AU.addRequired<DominatorTree>();
|
|
AU.addPreserved<DominatorTree>();
|
|
AU.addRequired<ScalarEvolution>();
|
|
AU.addPreserved<ScalarEvolution>();
|
|
AU.addRequired<IVUsers>();
|
|
AU.addPreserved<IVUsers>();
|
|
}
|
|
|
|
bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) {
|
|
bool Changed = false;
|
|
|
|
// Run the main LSR transformation.
|
|
Changed |= LSRInstance(TLI, L, this).getChanged();
|
|
|
|
// At this point, it is worth checking to see if any recurrence PHIs are also
|
|
// dead, so that we can remove them as well.
|
|
Changed |= DeleteDeadPHIs(L->getHeader());
|
|
|
|
return Changed;
|
|
}
|