mirror of
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46bdfb0e6b
to more accurately describe what it does. Expand its doxygen comment to describe what the backedge-taken count is and how it differs from the actual iteration count of the loop. Adjust names and comments in associated code accordingly. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@65382 91177308-0d34-0410-b5e6-96231b3b80d8
3209 lines
126 KiB
C++
3209 lines
126 KiB
C++
//===- ScalarEvolution.cpp - Scalar Evolution Analysis ----------*- C++ -*-===//
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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 file contains the implementation of the scalar evolution analysis
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// engine, which is used primarily to analyze expressions involving induction
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// variables in loops.
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//
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// There are several aspects to this library. First is the representation of
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// scalar expressions, which are represented as subclasses of the SCEV class.
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// These classes are used to represent certain types of subexpressions that we
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// can handle. These classes are reference counted, managed by the SCEVHandle
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// class. We only create one SCEV of a particular shape, so pointer-comparisons
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// for equality are legal.
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//
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// One important aspect of the SCEV objects is that they are never cyclic, even
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// if there is a cycle in the dataflow for an expression (ie, a PHI node). If
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// the PHI node is one of the idioms that we can represent (e.g., a polynomial
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// recurrence) then we represent it directly as a recurrence node, otherwise we
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// represent it as a SCEVUnknown node.
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//
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// In addition to being able to represent expressions of various types, we also
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// have folders that are used to build the *canonical* representation for a
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// particular expression. These folders are capable of using a variety of
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// rewrite rules to simplify the expressions.
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//
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// Once the folders are defined, we can implement the more interesting
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// higher-level code, such as the code that recognizes PHI nodes of various
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// types, computes the execution count of a loop, etc.
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//
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// TODO: We should use these routines and value representations to implement
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// dependence analysis!
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//
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//===----------------------------------------------------------------------===//
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//
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// There are several good references for the techniques used in this analysis.
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//
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// Chains of recurrences -- a method to expedite the evaluation
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// of closed-form functions
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// Olaf Bachmann, Paul S. Wang, Eugene V. Zima
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//
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// On computational properties of chains of recurrences
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// Eugene V. Zima
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//
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// Symbolic Evaluation of Chains of Recurrences for Loop Optimization
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// Robert A. van Engelen
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//
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// Efficient Symbolic Analysis for Optimizing Compilers
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// Robert A. van Engelen
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//
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// Using the chains of recurrences algebra for data dependence testing and
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// induction variable substitution
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// MS Thesis, Johnie Birch
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "scalar-evolution"
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#include "llvm/Analysis/ScalarEvolutionExpressions.h"
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#include "llvm/Constants.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/GlobalVariable.h"
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#include "llvm/Instructions.h"
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#include "llvm/Analysis/ConstantFolding.h"
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#include "llvm/Analysis/Dominators.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/Assembly/Writer.h"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Support/CFG.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/ConstantRange.h"
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#include "llvm/Support/InstIterator.h"
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#include "llvm/Support/ManagedStatic.h"
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#include "llvm/Support/MathExtras.h"
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#include "llvm/Support/Streams.h"
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#include "llvm/ADT/Statistic.h"
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#include <ostream>
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#include <algorithm>
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#include <cmath>
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using namespace llvm;
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STATISTIC(NumArrayLenItCounts,
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"Number of trip counts computed with array length");
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STATISTIC(NumTripCountsComputed,
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"Number of loops with predictable loop counts");
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STATISTIC(NumTripCountsNotComputed,
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"Number of loops without predictable loop counts");
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STATISTIC(NumBruteForceTripCountsComputed,
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"Number of loops with trip counts computed by force");
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static cl::opt<unsigned>
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MaxBruteForceIterations("scalar-evolution-max-iterations", cl::ReallyHidden,
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cl::desc("Maximum number of iterations SCEV will "
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"symbolically execute a constant derived loop"),
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cl::init(100));
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static RegisterPass<ScalarEvolution>
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R("scalar-evolution", "Scalar Evolution Analysis", false, true);
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char ScalarEvolution::ID = 0;
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//===----------------------------------------------------------------------===//
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// SCEV class definitions
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//===----------------------------------------------------------------------===//
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//===----------------------------------------------------------------------===//
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// Implementation of the SCEV class.
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//
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SCEV::~SCEV() {}
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void SCEV::dump() const {
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print(cerr);
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cerr << '\n';
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}
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uint32_t SCEV::getBitWidth() const {
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if (const IntegerType* ITy = dyn_cast<IntegerType>(getType()))
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return ITy->getBitWidth();
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return 0;
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}
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bool SCEV::isZero() const {
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if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
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return SC->getValue()->isZero();
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return false;
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}
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SCEVCouldNotCompute::SCEVCouldNotCompute() : SCEV(scCouldNotCompute) {}
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bool SCEVCouldNotCompute::isLoopInvariant(const Loop *L) const {
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assert(0 && "Attempt to use a SCEVCouldNotCompute object!");
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return false;
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}
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const Type *SCEVCouldNotCompute::getType() const {
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assert(0 && "Attempt to use a SCEVCouldNotCompute object!");
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return 0;
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}
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bool SCEVCouldNotCompute::hasComputableLoopEvolution(const Loop *L) const {
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assert(0 && "Attempt to use a SCEVCouldNotCompute object!");
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return false;
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}
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SCEVHandle SCEVCouldNotCompute::
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replaceSymbolicValuesWithConcrete(const SCEVHandle &Sym,
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const SCEVHandle &Conc,
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ScalarEvolution &SE) const {
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return this;
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}
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void SCEVCouldNotCompute::print(std::ostream &OS) const {
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OS << "***COULDNOTCOMPUTE***";
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}
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bool SCEVCouldNotCompute::classof(const SCEV *S) {
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return S->getSCEVType() == scCouldNotCompute;
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}
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// SCEVConstants - Only allow the creation of one SCEVConstant for any
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// particular value. Don't use a SCEVHandle here, or else the object will
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// never be deleted!
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static ManagedStatic<std::map<ConstantInt*, SCEVConstant*> > SCEVConstants;
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SCEVConstant::~SCEVConstant() {
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SCEVConstants->erase(V);
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}
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SCEVHandle ScalarEvolution::getConstant(ConstantInt *V) {
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SCEVConstant *&R = (*SCEVConstants)[V];
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if (R == 0) R = new SCEVConstant(V);
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return R;
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}
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SCEVHandle ScalarEvolution::getConstant(const APInt& Val) {
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return getConstant(ConstantInt::get(Val));
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}
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const Type *SCEVConstant::getType() const { return V->getType(); }
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void SCEVConstant::print(std::ostream &OS) const {
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WriteAsOperand(OS, V, false);
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}
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// SCEVTruncates - Only allow the creation of one SCEVTruncateExpr for any
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// particular input. Don't use a SCEVHandle here, or else the object will
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// never be deleted!
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static ManagedStatic<std::map<std::pair<SCEV*, const Type*>,
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SCEVTruncateExpr*> > SCEVTruncates;
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SCEVTruncateExpr::SCEVTruncateExpr(const SCEVHandle &op, const Type *ty)
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: SCEV(scTruncate), Op(op), Ty(ty) {
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assert(Op->getType()->isInteger() && Ty->isInteger() &&
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"Cannot truncate non-integer value!");
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assert(Op->getType()->getPrimitiveSizeInBits() > Ty->getPrimitiveSizeInBits()
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&& "This is not a truncating conversion!");
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}
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SCEVTruncateExpr::~SCEVTruncateExpr() {
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SCEVTruncates->erase(std::make_pair(Op, Ty));
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}
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bool SCEVTruncateExpr::dominates(BasicBlock *BB, DominatorTree *DT) const {
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return Op->dominates(BB, DT);
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}
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void SCEVTruncateExpr::print(std::ostream &OS) const {
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OS << "(truncate " << *Op << " to " << *Ty << ")";
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}
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// SCEVZeroExtends - Only allow the creation of one SCEVZeroExtendExpr for any
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// particular input. Don't use a SCEVHandle here, or else the object will never
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// be deleted!
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static ManagedStatic<std::map<std::pair<SCEV*, const Type*>,
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SCEVZeroExtendExpr*> > SCEVZeroExtends;
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SCEVZeroExtendExpr::SCEVZeroExtendExpr(const SCEVHandle &op, const Type *ty)
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: SCEV(scZeroExtend), Op(op), Ty(ty) {
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assert(Op->getType()->isInteger() && Ty->isInteger() &&
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"Cannot zero extend non-integer value!");
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assert(Op->getType()->getPrimitiveSizeInBits() < Ty->getPrimitiveSizeInBits()
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&& "This is not an extending conversion!");
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}
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SCEVZeroExtendExpr::~SCEVZeroExtendExpr() {
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SCEVZeroExtends->erase(std::make_pair(Op, Ty));
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}
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bool SCEVZeroExtendExpr::dominates(BasicBlock *BB, DominatorTree *DT) const {
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return Op->dominates(BB, DT);
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}
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void SCEVZeroExtendExpr::print(std::ostream &OS) const {
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OS << "(zeroextend " << *Op << " to " << *Ty << ")";
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}
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// SCEVSignExtends - Only allow the creation of one SCEVSignExtendExpr for any
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// particular input. Don't use a SCEVHandle here, or else the object will never
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// be deleted!
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static ManagedStatic<std::map<std::pair<SCEV*, const Type*>,
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SCEVSignExtendExpr*> > SCEVSignExtends;
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SCEVSignExtendExpr::SCEVSignExtendExpr(const SCEVHandle &op, const Type *ty)
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: SCEV(scSignExtend), Op(op), Ty(ty) {
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assert(Op->getType()->isInteger() && Ty->isInteger() &&
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"Cannot sign extend non-integer value!");
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assert(Op->getType()->getPrimitiveSizeInBits() < Ty->getPrimitiveSizeInBits()
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&& "This is not an extending conversion!");
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}
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SCEVSignExtendExpr::~SCEVSignExtendExpr() {
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SCEVSignExtends->erase(std::make_pair(Op, Ty));
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}
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bool SCEVSignExtendExpr::dominates(BasicBlock *BB, DominatorTree *DT) const {
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return Op->dominates(BB, DT);
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}
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void SCEVSignExtendExpr::print(std::ostream &OS) const {
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OS << "(signextend " << *Op << " to " << *Ty << ")";
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}
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// SCEVCommExprs - Only allow the creation of one SCEVCommutativeExpr for any
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// particular input. Don't use a SCEVHandle here, or else the object will never
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// be deleted!
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static ManagedStatic<std::map<std::pair<unsigned, std::vector<SCEV*> >,
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SCEVCommutativeExpr*> > SCEVCommExprs;
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SCEVCommutativeExpr::~SCEVCommutativeExpr() {
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SCEVCommExprs->erase(std::make_pair(getSCEVType(),
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std::vector<SCEV*>(Operands.begin(),
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Operands.end())));
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}
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void SCEVCommutativeExpr::print(std::ostream &OS) const {
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assert(Operands.size() > 1 && "This plus expr shouldn't exist!");
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const char *OpStr = getOperationStr();
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OS << "(" << *Operands[0];
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for (unsigned i = 1, e = Operands.size(); i != e; ++i)
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OS << OpStr << *Operands[i];
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OS << ")";
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}
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SCEVHandle SCEVCommutativeExpr::
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replaceSymbolicValuesWithConcrete(const SCEVHandle &Sym,
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const SCEVHandle &Conc,
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ScalarEvolution &SE) const {
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for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
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SCEVHandle H =
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getOperand(i)->replaceSymbolicValuesWithConcrete(Sym, Conc, SE);
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if (H != getOperand(i)) {
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std::vector<SCEVHandle> NewOps;
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NewOps.reserve(getNumOperands());
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for (unsigned j = 0; j != i; ++j)
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NewOps.push_back(getOperand(j));
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NewOps.push_back(H);
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for (++i; i != e; ++i)
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NewOps.push_back(getOperand(i)->
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replaceSymbolicValuesWithConcrete(Sym, Conc, SE));
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if (isa<SCEVAddExpr>(this))
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return SE.getAddExpr(NewOps);
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else if (isa<SCEVMulExpr>(this))
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return SE.getMulExpr(NewOps);
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else if (isa<SCEVSMaxExpr>(this))
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return SE.getSMaxExpr(NewOps);
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else if (isa<SCEVUMaxExpr>(this))
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return SE.getUMaxExpr(NewOps);
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else
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assert(0 && "Unknown commutative expr!");
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}
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}
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return this;
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}
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bool SCEVCommutativeExpr::dominates(BasicBlock *BB, DominatorTree *DT) const {
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for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
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if (!getOperand(i)->dominates(BB, DT))
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return false;
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}
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return true;
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}
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// SCEVUDivs - Only allow the creation of one SCEVUDivExpr for any particular
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// input. Don't use a SCEVHandle here, or else the object will never be
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// deleted!
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static ManagedStatic<std::map<std::pair<SCEV*, SCEV*>,
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SCEVUDivExpr*> > SCEVUDivs;
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SCEVUDivExpr::~SCEVUDivExpr() {
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SCEVUDivs->erase(std::make_pair(LHS, RHS));
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}
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bool SCEVUDivExpr::dominates(BasicBlock *BB, DominatorTree *DT) const {
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return LHS->dominates(BB, DT) && RHS->dominates(BB, DT);
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}
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void SCEVUDivExpr::print(std::ostream &OS) const {
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OS << "(" << *LHS << " /u " << *RHS << ")";
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}
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const Type *SCEVUDivExpr::getType() const {
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return LHS->getType();
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}
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// SCEVAddRecExprs - Only allow the creation of one SCEVAddRecExpr for any
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// particular input. Don't use a SCEVHandle here, or else the object will never
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// be deleted!
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static ManagedStatic<std::map<std::pair<const Loop *, std::vector<SCEV*> >,
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SCEVAddRecExpr*> > SCEVAddRecExprs;
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SCEVAddRecExpr::~SCEVAddRecExpr() {
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SCEVAddRecExprs->erase(std::make_pair(L,
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std::vector<SCEV*>(Operands.begin(),
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Operands.end())));
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}
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bool SCEVAddRecExpr::dominates(BasicBlock *BB, DominatorTree *DT) const {
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for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
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if (!getOperand(i)->dominates(BB, DT))
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return false;
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}
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return true;
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}
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SCEVHandle SCEVAddRecExpr::
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replaceSymbolicValuesWithConcrete(const SCEVHandle &Sym,
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const SCEVHandle &Conc,
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ScalarEvolution &SE) const {
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for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
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SCEVHandle H =
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getOperand(i)->replaceSymbolicValuesWithConcrete(Sym, Conc, SE);
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if (H != getOperand(i)) {
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std::vector<SCEVHandle> NewOps;
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NewOps.reserve(getNumOperands());
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for (unsigned j = 0; j != i; ++j)
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NewOps.push_back(getOperand(j));
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NewOps.push_back(H);
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for (++i; i != e; ++i)
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NewOps.push_back(getOperand(i)->
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replaceSymbolicValuesWithConcrete(Sym, Conc, SE));
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return SE.getAddRecExpr(NewOps, L);
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}
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}
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return this;
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}
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bool SCEVAddRecExpr::isLoopInvariant(const Loop *QueryLoop) const {
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// This recurrence is invariant w.r.t to QueryLoop iff QueryLoop doesn't
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// contain L and if the start is invariant.
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return !QueryLoop->contains(L->getHeader()) &&
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getOperand(0)->isLoopInvariant(QueryLoop);
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}
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void SCEVAddRecExpr::print(std::ostream &OS) const {
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OS << "{" << *Operands[0];
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for (unsigned i = 1, e = Operands.size(); i != e; ++i)
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OS << ",+," << *Operands[i];
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OS << "}<" << L->getHeader()->getName() + ">";
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}
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// SCEVUnknowns - Only allow the creation of one SCEVUnknown for any particular
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// value. Don't use a SCEVHandle here, or else the object will never be
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// deleted!
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static ManagedStatic<std::map<Value*, SCEVUnknown*> > SCEVUnknowns;
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SCEVUnknown::~SCEVUnknown() { SCEVUnknowns->erase(V); }
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bool SCEVUnknown::isLoopInvariant(const Loop *L) const {
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// All non-instruction values are loop invariant. All instructions are loop
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// invariant if they are not contained in the specified loop.
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if (Instruction *I = dyn_cast<Instruction>(V))
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return !L->contains(I->getParent());
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return true;
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}
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bool SCEVUnknown::dominates(BasicBlock *BB, DominatorTree *DT) const {
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if (Instruction *I = dyn_cast<Instruction>(getValue()))
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return DT->dominates(I->getParent(), BB);
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return true;
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}
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const Type *SCEVUnknown::getType() const {
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return V->getType();
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}
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void SCEVUnknown::print(std::ostream &OS) const {
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WriteAsOperand(OS, V, false);
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}
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//===----------------------------------------------------------------------===//
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// SCEV Utilities
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//===----------------------------------------------------------------------===//
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namespace {
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/// SCEVComplexityCompare - Return true if the complexity of the LHS is less
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/// than the complexity of the RHS. This comparator is used to canonicalize
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/// expressions.
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struct VISIBILITY_HIDDEN SCEVComplexityCompare {
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bool operator()(const SCEV *LHS, const SCEV *RHS) const {
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return LHS->getSCEVType() < RHS->getSCEVType();
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}
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};
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}
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/// GroupByComplexity - Given a list of SCEV objects, order them by their
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/// complexity, and group objects of the same complexity together by value.
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/// When this routine is finished, we know that any duplicates in the vector are
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/// consecutive and that complexity is monotonically increasing.
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///
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/// Note that we go take special precautions to ensure that we get determinstic
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/// results from this routine. In other words, we don't want the results of
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/// this to depend on where the addresses of various SCEV objects happened to
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/// land in memory.
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///
|
|
static void GroupByComplexity(std::vector<SCEVHandle> &Ops) {
|
|
if (Ops.size() < 2) return; // Noop
|
|
if (Ops.size() == 2) {
|
|
// This is the common case, which also happens to be trivially simple.
|
|
// Special case it.
|
|
if (SCEVComplexityCompare()(Ops[1], Ops[0]))
|
|
std::swap(Ops[0], Ops[1]);
|
|
return;
|
|
}
|
|
|
|
// Do the rough sort by complexity.
|
|
std::sort(Ops.begin(), Ops.end(), SCEVComplexityCompare());
|
|
|
|
// Now that we are sorted by complexity, group elements of the same
|
|
// complexity. Note that this is, at worst, N^2, but the vector is likely to
|
|
// be extremely short in practice. Note that we take this approach because we
|
|
// do not want to depend on the addresses of the objects we are grouping.
|
|
for (unsigned i = 0, e = Ops.size(); i != e-2; ++i) {
|
|
SCEV *S = Ops[i];
|
|
unsigned Complexity = S->getSCEVType();
|
|
|
|
// If there are any objects of the same complexity and same value as this
|
|
// one, group them.
|
|
for (unsigned j = i+1; j != e && Ops[j]->getSCEVType() == Complexity; ++j) {
|
|
if (Ops[j] == S) { // Found a duplicate.
|
|
// Move it to immediately after i'th element.
|
|
std::swap(Ops[i+1], Ops[j]);
|
|
++i; // no need to rescan it.
|
|
if (i == e-2) return; // Done!
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// Simple SCEV method implementations
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
/// getIntegerSCEV - Given an integer or FP type, create a constant for the
|
|
/// specified signed integer value and return a SCEV for the constant.
|
|
SCEVHandle ScalarEvolution::getIntegerSCEV(int Val, const Type *Ty) {
|
|
Constant *C;
|
|
if (Val == 0)
|
|
C = Constant::getNullValue(Ty);
|
|
else if (Ty->isFloatingPoint())
|
|
C = ConstantFP::get(APFloat(Ty==Type::FloatTy ? APFloat::IEEEsingle :
|
|
APFloat::IEEEdouble, Val));
|
|
else
|
|
C = ConstantInt::get(Ty, Val);
|
|
return getUnknown(C);
|
|
}
|
|
|
|
/// getNegativeSCEV - Return a SCEV corresponding to -V = -1*V
|
|
///
|
|
SCEVHandle ScalarEvolution::getNegativeSCEV(const SCEVHandle &V) {
|
|
if (SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
|
|
return getUnknown(ConstantExpr::getNeg(VC->getValue()));
|
|
|
|
return getMulExpr(V, getConstant(ConstantInt::getAllOnesValue(V->getType())));
|
|
}
|
|
|
|
/// getNotSCEV - Return a SCEV corresponding to ~V = -1-V
|
|
SCEVHandle ScalarEvolution::getNotSCEV(const SCEVHandle &V) {
|
|
if (SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
|
|
return getUnknown(ConstantExpr::getNot(VC->getValue()));
|
|
|
|
SCEVHandle AllOnes = getConstant(ConstantInt::getAllOnesValue(V->getType()));
|
|
return getMinusSCEV(AllOnes, V);
|
|
}
|
|
|
|
/// getMinusSCEV - Return a SCEV corresponding to LHS - RHS.
|
|
///
|
|
SCEVHandle ScalarEvolution::getMinusSCEV(const SCEVHandle &LHS,
|
|
const SCEVHandle &RHS) {
|
|
// X - Y --> X + -Y
|
|
return getAddExpr(LHS, getNegativeSCEV(RHS));
|
|
}
|
|
|
|
|
|
/// BinomialCoefficient - Compute BC(It, K). The result has width W.
|
|
// Assume, K > 0.
|
|
static SCEVHandle BinomialCoefficient(SCEVHandle It, unsigned K,
|
|
ScalarEvolution &SE,
|
|
const IntegerType* ResultTy) {
|
|
// Handle the simplest case efficiently.
|
|
if (K == 1)
|
|
return SE.getTruncateOrZeroExtend(It, ResultTy);
|
|
|
|
// We are using the following formula for BC(It, K):
|
|
//
|
|
// BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / K!
|
|
//
|
|
// Suppose, W is the bitwidth of the return value. We must be prepared for
|
|
// overflow. Hence, we must assure that the result of our computation is
|
|
// equal to the accurate one modulo 2^W. Unfortunately, division isn't
|
|
// safe in modular arithmetic.
|
|
//
|
|
// However, this code doesn't use exactly that formula; the formula it uses
|
|
// is something like the following, where T is the number of factors of 2 in
|
|
// K! (i.e. trailing zeros in the binary representation of K!), and ^ is
|
|
// exponentiation:
|
|
//
|
|
// BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / 2^T / (K! / 2^T)
|
|
//
|
|
// This formula is trivially equivalent to the previous formula. However,
|
|
// this formula can be implemented much more efficiently. The trick is that
|
|
// K! / 2^T is odd, and exact division by an odd number *is* safe in modular
|
|
// arithmetic. To do exact division in modular arithmetic, all we have
|
|
// to do is multiply by the inverse. Therefore, this step can be done at
|
|
// width W.
|
|
//
|
|
// The next issue is how to safely do the division by 2^T. The way this
|
|
// is done is by doing the multiplication step at a width of at least W + T
|
|
// bits. This way, the bottom W+T bits of the product are accurate. Then,
|
|
// when we perform the division by 2^T (which is equivalent to a right shift
|
|
// by T), the bottom W bits are accurate. Extra bits are okay; they'll get
|
|
// truncated out after the division by 2^T.
|
|
//
|
|
// In comparison to just directly using the first formula, this technique
|
|
// is much more efficient; using the first formula requires W * K bits,
|
|
// but this formula less than W + K bits. Also, the first formula requires
|
|
// a division step, whereas this formula only requires multiplies and shifts.
|
|
//
|
|
// It doesn't matter whether the subtraction step is done in the calculation
|
|
// width or the input iteration count's width; if the subtraction overflows,
|
|
// the result must be zero anyway. We prefer here to do it in the width of
|
|
// the induction variable because it helps a lot for certain cases; CodeGen
|
|
// isn't smart enough to ignore the overflow, which leads to much less
|
|
// efficient code if the width of the subtraction is wider than the native
|
|
// register width.
|
|
//
|
|
// (It's possible to not widen at all by pulling out factors of 2 before
|
|
// the multiplication; for example, K=2 can be calculated as
|
|
// It/2*(It+(It*INT_MIN/INT_MIN)+-1). However, it requires
|
|
// extra arithmetic, so it's not an obvious win, and it gets
|
|
// much more complicated for K > 3.)
|
|
|
|
// Protection from insane SCEVs; this bound is conservative,
|
|
// but it probably doesn't matter.
|
|
if (K > 1000)
|
|
return new SCEVCouldNotCompute();
|
|
|
|
unsigned W = ResultTy->getBitWidth();
|
|
|
|
// Calculate K! / 2^T and T; we divide out the factors of two before
|
|
// multiplying for calculating K! / 2^T to avoid overflow.
|
|
// Other overflow doesn't matter because we only care about the bottom
|
|
// W bits of the result.
|
|
APInt OddFactorial(W, 1);
|
|
unsigned T = 1;
|
|
for (unsigned i = 3; i <= K; ++i) {
|
|
APInt Mult(W, i);
|
|
unsigned TwoFactors = Mult.countTrailingZeros();
|
|
T += TwoFactors;
|
|
Mult = Mult.lshr(TwoFactors);
|
|
OddFactorial *= Mult;
|
|
}
|
|
|
|
// We need at least W + T bits for the multiplication step
|
|
unsigned CalculationBits = W + T;
|
|
|
|
// Calcuate 2^T, at width T+W.
|
|
APInt DivFactor = APInt(CalculationBits, 1).shl(T);
|
|
|
|
// Calculate the multiplicative inverse of K! / 2^T;
|
|
// this multiplication factor will perform the exact division by
|
|
// K! / 2^T.
|
|
APInt Mod = APInt::getSignedMinValue(W+1);
|
|
APInt MultiplyFactor = OddFactorial.zext(W+1);
|
|
MultiplyFactor = MultiplyFactor.multiplicativeInverse(Mod);
|
|
MultiplyFactor = MultiplyFactor.trunc(W);
|
|
|
|
// Calculate the product, at width T+W
|
|
const IntegerType *CalculationTy = IntegerType::get(CalculationBits);
|
|
SCEVHandle Dividend = SE.getTruncateOrZeroExtend(It, CalculationTy);
|
|
for (unsigned i = 1; i != K; ++i) {
|
|
SCEVHandle S = SE.getMinusSCEV(It, SE.getIntegerSCEV(i, It->getType()));
|
|
Dividend = SE.getMulExpr(Dividend,
|
|
SE.getTruncateOrZeroExtend(S, CalculationTy));
|
|
}
|
|
|
|
// Divide by 2^T
|
|
SCEVHandle DivResult = SE.getUDivExpr(Dividend, SE.getConstant(DivFactor));
|
|
|
|
// Truncate the result, and divide by K! / 2^T.
|
|
|
|
return SE.getMulExpr(SE.getConstant(MultiplyFactor),
|
|
SE.getTruncateOrZeroExtend(DivResult, ResultTy));
|
|
}
|
|
|
|
/// evaluateAtIteration - Return the value of this chain of recurrences at
|
|
/// the specified iteration number. We can evaluate this recurrence by
|
|
/// multiplying each element in the chain by the binomial coefficient
|
|
/// corresponding to it. In other words, we can evaluate {A,+,B,+,C,+,D} as:
|
|
///
|
|
/// A*BC(It, 0) + B*BC(It, 1) + C*BC(It, 2) + D*BC(It, 3)
|
|
///
|
|
/// where BC(It, k) stands for binomial coefficient.
|
|
///
|
|
SCEVHandle SCEVAddRecExpr::evaluateAtIteration(SCEVHandle It,
|
|
ScalarEvolution &SE) const {
|
|
SCEVHandle Result = getStart();
|
|
for (unsigned i = 1, e = getNumOperands(); i != e; ++i) {
|
|
// The computation is correct in the face of overflow provided that the
|
|
// multiplication is performed _after_ the evaluation of the binomial
|
|
// coefficient.
|
|
SCEVHandle Coeff = BinomialCoefficient(It, i, SE,
|
|
cast<IntegerType>(getType()));
|
|
if (isa<SCEVCouldNotCompute>(Coeff))
|
|
return Coeff;
|
|
|
|
Result = SE.getAddExpr(Result, SE.getMulExpr(getOperand(i), Coeff));
|
|
}
|
|
return Result;
|
|
}
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// SCEV Expression folder implementations
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
SCEVHandle ScalarEvolution::getTruncateExpr(const SCEVHandle &Op, const Type *Ty) {
|
|
if (SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
|
|
return getUnknown(
|
|
ConstantExpr::getTrunc(SC->getValue(), Ty));
|
|
|
|
// If the input value is a chrec scev made out of constants, truncate
|
|
// all of the constants.
|
|
if (SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(Op)) {
|
|
std::vector<SCEVHandle> Operands;
|
|
for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
|
|
// FIXME: This should allow truncation of other expression types!
|
|
if (isa<SCEVConstant>(AddRec->getOperand(i)))
|
|
Operands.push_back(getTruncateExpr(AddRec->getOperand(i), Ty));
|
|
else
|
|
break;
|
|
if (Operands.size() == AddRec->getNumOperands())
|
|
return getAddRecExpr(Operands, AddRec->getLoop());
|
|
}
|
|
|
|
SCEVTruncateExpr *&Result = (*SCEVTruncates)[std::make_pair(Op, Ty)];
|
|
if (Result == 0) Result = new SCEVTruncateExpr(Op, Ty);
|
|
return Result;
|
|
}
|
|
|
|
SCEVHandle ScalarEvolution::getZeroExtendExpr(const SCEVHandle &Op, const Type *Ty) {
|
|
if (SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
|
|
return getUnknown(
|
|
ConstantExpr::getZExt(SC->getValue(), Ty));
|
|
|
|
// FIXME: If the input value is a chrec scev, and we can prove that the value
|
|
// did not overflow the old, smaller, value, we can zero extend all of the
|
|
// operands (often constants). This would allow analysis of something like
|
|
// this: for (unsigned char X = 0; X < 100; ++X) { int Y = X; }
|
|
|
|
SCEVZeroExtendExpr *&Result = (*SCEVZeroExtends)[std::make_pair(Op, Ty)];
|
|
if (Result == 0) Result = new SCEVZeroExtendExpr(Op, Ty);
|
|
return Result;
|
|
}
|
|
|
|
SCEVHandle ScalarEvolution::getSignExtendExpr(const SCEVHandle &Op, const Type *Ty) {
|
|
if (SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
|
|
return getUnknown(
|
|
ConstantExpr::getSExt(SC->getValue(), Ty));
|
|
|
|
// FIXME: If the input value is a chrec scev, and we can prove that the value
|
|
// did not overflow the old, smaller, value, we can sign extend all of the
|
|
// operands (often constants). This would allow analysis of something like
|
|
// this: for (signed char X = 0; X < 100; ++X) { int Y = X; }
|
|
|
|
SCEVSignExtendExpr *&Result = (*SCEVSignExtends)[std::make_pair(Op, Ty)];
|
|
if (Result == 0) Result = new SCEVSignExtendExpr(Op, Ty);
|
|
return Result;
|
|
}
|
|
|
|
/// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion
|
|
/// of the input value to the specified type. If the type must be
|
|
/// extended, it is zero extended.
|
|
SCEVHandle ScalarEvolution::getTruncateOrZeroExtend(const SCEVHandle &V,
|
|
const Type *Ty) {
|
|
const Type *SrcTy = V->getType();
|
|
assert(SrcTy->isInteger() && Ty->isInteger() &&
|
|
"Cannot truncate or zero extend with non-integer arguments!");
|
|
if (SrcTy->getPrimitiveSizeInBits() == Ty->getPrimitiveSizeInBits())
|
|
return V; // No conversion
|
|
if (SrcTy->getPrimitiveSizeInBits() > Ty->getPrimitiveSizeInBits())
|
|
return getTruncateExpr(V, Ty);
|
|
return getZeroExtendExpr(V, Ty);
|
|
}
|
|
|
|
/// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion
|
|
/// of the input value to the specified type. If the type must be
|
|
/// extended, it is sign extended.
|
|
SCEVHandle ScalarEvolution::getTruncateOrSignExtend(const SCEVHandle &V,
|
|
const Type *Ty) {
|
|
const Type *SrcTy = V->getType();
|
|
assert(SrcTy->isInteger() && Ty->isInteger() &&
|
|
"Cannot truncate or sign extend with non-integer arguments!");
|
|
if (SrcTy->getPrimitiveSizeInBits() == Ty->getPrimitiveSizeInBits())
|
|
return V; // No conversion
|
|
if (SrcTy->getPrimitiveSizeInBits() > Ty->getPrimitiveSizeInBits())
|
|
return getTruncateExpr(V, Ty);
|
|
return getSignExtendExpr(V, Ty);
|
|
}
|
|
|
|
// get - Get a canonical add expression, or something simpler if possible.
|
|
SCEVHandle ScalarEvolution::getAddExpr(std::vector<SCEVHandle> &Ops) {
|
|
assert(!Ops.empty() && "Cannot get empty add!");
|
|
if (Ops.size() == 1) return Ops[0];
|
|
|
|
// Sort by complexity, this groups all similar expression types together.
|
|
GroupByComplexity(Ops);
|
|
|
|
// If there are any constants, fold them together.
|
|
unsigned Idx = 0;
|
|
if (SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
|
|
++Idx;
|
|
assert(Idx < Ops.size());
|
|
while (SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
|
|
// We found two constants, fold them together!
|
|
ConstantInt *Fold = ConstantInt::get(LHSC->getValue()->getValue() +
|
|
RHSC->getValue()->getValue());
|
|
Ops[0] = getConstant(Fold);
|
|
Ops.erase(Ops.begin()+1); // Erase the folded element
|
|
if (Ops.size() == 1) return Ops[0];
|
|
LHSC = cast<SCEVConstant>(Ops[0]);
|
|
}
|
|
|
|
// If we are left with a constant zero being added, strip it off.
|
|
if (cast<SCEVConstant>(Ops[0])->getValue()->isZero()) {
|
|
Ops.erase(Ops.begin());
|
|
--Idx;
|
|
}
|
|
}
|
|
|
|
if (Ops.size() == 1) return Ops[0];
|
|
|
|
// Okay, check to see if the same value occurs in the operand list twice. If
|
|
// so, merge them together into an multiply expression. Since we sorted the
|
|
// list, these values are required to be adjacent.
|
|
const Type *Ty = Ops[0]->getType();
|
|
for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
|
|
if (Ops[i] == Ops[i+1]) { // X + Y + Y --> X + Y*2
|
|
// Found a match, merge the two values into a multiply, and add any
|
|
// remaining values to the result.
|
|
SCEVHandle Two = getIntegerSCEV(2, Ty);
|
|
SCEVHandle Mul = getMulExpr(Ops[i], Two);
|
|
if (Ops.size() == 2)
|
|
return Mul;
|
|
Ops.erase(Ops.begin()+i, Ops.begin()+i+2);
|
|
Ops.push_back(Mul);
|
|
return getAddExpr(Ops);
|
|
}
|
|
|
|
// Now we know the first non-constant operand. Skip past any cast SCEVs.
|
|
while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddExpr)
|
|
++Idx;
|
|
|
|
// If there are add operands they would be next.
|
|
if (Idx < Ops.size()) {
|
|
bool DeletedAdd = false;
|
|
while (SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[Idx])) {
|
|
// If we have an add, expand the add operands onto the end of the operands
|
|
// list.
|
|
Ops.insert(Ops.end(), Add->op_begin(), Add->op_end());
|
|
Ops.erase(Ops.begin()+Idx);
|
|
DeletedAdd = true;
|
|
}
|
|
|
|
// If we deleted at least one add, we added operands to the end of the list,
|
|
// and they are not necessarily sorted. Recurse to resort and resimplify
|
|
// any operands we just aquired.
|
|
if (DeletedAdd)
|
|
return getAddExpr(Ops);
|
|
}
|
|
|
|
// Skip over the add expression until we get to a multiply.
|
|
while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
|
|
++Idx;
|
|
|
|
// If we are adding something to a multiply expression, make sure the
|
|
// something is not already an operand of the multiply. If so, merge it into
|
|
// the multiply.
|
|
for (; Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx]); ++Idx) {
|
|
SCEVMulExpr *Mul = cast<SCEVMulExpr>(Ops[Idx]);
|
|
for (unsigned MulOp = 0, e = Mul->getNumOperands(); MulOp != e; ++MulOp) {
|
|
SCEV *MulOpSCEV = Mul->getOperand(MulOp);
|
|
for (unsigned AddOp = 0, e = Ops.size(); AddOp != e; ++AddOp)
|
|
if (MulOpSCEV == Ops[AddOp] && !isa<SCEVConstant>(MulOpSCEV)) {
|
|
// Fold W + X + (X * Y * Z) --> W + (X * ((Y*Z)+1))
|
|
SCEVHandle InnerMul = Mul->getOperand(MulOp == 0);
|
|
if (Mul->getNumOperands() != 2) {
|
|
// If the multiply has more than two operands, we must get the
|
|
// Y*Z term.
|
|
std::vector<SCEVHandle> MulOps(Mul->op_begin(), Mul->op_end());
|
|
MulOps.erase(MulOps.begin()+MulOp);
|
|
InnerMul = getMulExpr(MulOps);
|
|
}
|
|
SCEVHandle One = getIntegerSCEV(1, Ty);
|
|
SCEVHandle AddOne = getAddExpr(InnerMul, One);
|
|
SCEVHandle OuterMul = getMulExpr(AddOne, Ops[AddOp]);
|
|
if (Ops.size() == 2) return OuterMul;
|
|
if (AddOp < Idx) {
|
|
Ops.erase(Ops.begin()+AddOp);
|
|
Ops.erase(Ops.begin()+Idx-1);
|
|
} else {
|
|
Ops.erase(Ops.begin()+Idx);
|
|
Ops.erase(Ops.begin()+AddOp-1);
|
|
}
|
|
Ops.push_back(OuterMul);
|
|
return getAddExpr(Ops);
|
|
}
|
|
|
|
// Check this multiply against other multiplies being added together.
|
|
for (unsigned OtherMulIdx = Idx+1;
|
|
OtherMulIdx < Ops.size() && isa<SCEVMulExpr>(Ops[OtherMulIdx]);
|
|
++OtherMulIdx) {
|
|
SCEVMulExpr *OtherMul = cast<SCEVMulExpr>(Ops[OtherMulIdx]);
|
|
// If MulOp occurs in OtherMul, we can fold the two multiplies
|
|
// together.
|
|
for (unsigned OMulOp = 0, e = OtherMul->getNumOperands();
|
|
OMulOp != e; ++OMulOp)
|
|
if (OtherMul->getOperand(OMulOp) == MulOpSCEV) {
|
|
// Fold X + (A*B*C) + (A*D*E) --> X + (A*(B*C+D*E))
|
|
SCEVHandle InnerMul1 = Mul->getOperand(MulOp == 0);
|
|
if (Mul->getNumOperands() != 2) {
|
|
std::vector<SCEVHandle> MulOps(Mul->op_begin(), Mul->op_end());
|
|
MulOps.erase(MulOps.begin()+MulOp);
|
|
InnerMul1 = getMulExpr(MulOps);
|
|
}
|
|
SCEVHandle InnerMul2 = OtherMul->getOperand(OMulOp == 0);
|
|
if (OtherMul->getNumOperands() != 2) {
|
|
std::vector<SCEVHandle> MulOps(OtherMul->op_begin(),
|
|
OtherMul->op_end());
|
|
MulOps.erase(MulOps.begin()+OMulOp);
|
|
InnerMul2 = getMulExpr(MulOps);
|
|
}
|
|
SCEVHandle InnerMulSum = getAddExpr(InnerMul1,InnerMul2);
|
|
SCEVHandle OuterMul = getMulExpr(MulOpSCEV, InnerMulSum);
|
|
if (Ops.size() == 2) return OuterMul;
|
|
Ops.erase(Ops.begin()+Idx);
|
|
Ops.erase(Ops.begin()+OtherMulIdx-1);
|
|
Ops.push_back(OuterMul);
|
|
return getAddExpr(Ops);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// If there are any add recurrences in the operands list, see if any other
|
|
// added values are loop invariant. If so, we can fold them into the
|
|
// recurrence.
|
|
while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
|
|
++Idx;
|
|
|
|
// Scan over all recurrences, trying to fold loop invariants into them.
|
|
for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
|
|
// Scan all of the other operands to this add and add them to the vector if
|
|
// they are loop invariant w.r.t. the recurrence.
|
|
std::vector<SCEVHandle> LIOps;
|
|
SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
|
|
for (unsigned i = 0, e = Ops.size(); i != e; ++i)
|
|
if (Ops[i]->isLoopInvariant(AddRec->getLoop())) {
|
|
LIOps.push_back(Ops[i]);
|
|
Ops.erase(Ops.begin()+i);
|
|
--i; --e;
|
|
}
|
|
|
|
// If we found some loop invariants, fold them into the recurrence.
|
|
if (!LIOps.empty()) {
|
|
// NLI + LI + {Start,+,Step} --> NLI + {LI+Start,+,Step}
|
|
LIOps.push_back(AddRec->getStart());
|
|
|
|
std::vector<SCEVHandle> AddRecOps(AddRec->op_begin(), AddRec->op_end());
|
|
AddRecOps[0] = getAddExpr(LIOps);
|
|
|
|
SCEVHandle NewRec = getAddRecExpr(AddRecOps, AddRec->getLoop());
|
|
// If all of the other operands were loop invariant, we are done.
|
|
if (Ops.size() == 1) return NewRec;
|
|
|
|
// Otherwise, add the folded AddRec by the non-liv parts.
|
|
for (unsigned i = 0;; ++i)
|
|
if (Ops[i] == AddRec) {
|
|
Ops[i] = NewRec;
|
|
break;
|
|
}
|
|
return getAddExpr(Ops);
|
|
}
|
|
|
|
// Okay, if there weren't any loop invariants to be folded, check to see if
|
|
// there are multiple AddRec's with the same loop induction variable being
|
|
// added together. If so, we can fold them.
|
|
for (unsigned OtherIdx = Idx+1;
|
|
OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);++OtherIdx)
|
|
if (OtherIdx != Idx) {
|
|
SCEVAddRecExpr *OtherAddRec = cast<SCEVAddRecExpr>(Ops[OtherIdx]);
|
|
if (AddRec->getLoop() == OtherAddRec->getLoop()) {
|
|
// Other + {A,+,B} + {C,+,D} --> Other + {A+C,+,B+D}
|
|
std::vector<SCEVHandle> NewOps(AddRec->op_begin(), AddRec->op_end());
|
|
for (unsigned i = 0, e = OtherAddRec->getNumOperands(); i != e; ++i) {
|
|
if (i >= NewOps.size()) {
|
|
NewOps.insert(NewOps.end(), OtherAddRec->op_begin()+i,
|
|
OtherAddRec->op_end());
|
|
break;
|
|
}
|
|
NewOps[i] = getAddExpr(NewOps[i], OtherAddRec->getOperand(i));
|
|
}
|
|
SCEVHandle NewAddRec = getAddRecExpr(NewOps, AddRec->getLoop());
|
|
|
|
if (Ops.size() == 2) return NewAddRec;
|
|
|
|
Ops.erase(Ops.begin()+Idx);
|
|
Ops.erase(Ops.begin()+OtherIdx-1);
|
|
Ops.push_back(NewAddRec);
|
|
return getAddExpr(Ops);
|
|
}
|
|
}
|
|
|
|
// Otherwise couldn't fold anything into this recurrence. Move onto the
|
|
// next one.
|
|
}
|
|
|
|
// Okay, it looks like we really DO need an add expr. Check to see if we
|
|
// already have one, otherwise create a new one.
|
|
std::vector<SCEV*> SCEVOps(Ops.begin(), Ops.end());
|
|
SCEVCommutativeExpr *&Result = (*SCEVCommExprs)[std::make_pair(scAddExpr,
|
|
SCEVOps)];
|
|
if (Result == 0) Result = new SCEVAddExpr(Ops);
|
|
return Result;
|
|
}
|
|
|
|
|
|
SCEVHandle ScalarEvolution::getMulExpr(std::vector<SCEVHandle> &Ops) {
|
|
assert(!Ops.empty() && "Cannot get empty mul!");
|
|
|
|
// Sort by complexity, this groups all similar expression types together.
|
|
GroupByComplexity(Ops);
|
|
|
|
// If there are any constants, fold them together.
|
|
unsigned Idx = 0;
|
|
if (SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
|
|
|
|
// C1*(C2+V) -> C1*C2 + C1*V
|
|
if (Ops.size() == 2)
|
|
if (SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1]))
|
|
if (Add->getNumOperands() == 2 &&
|
|
isa<SCEVConstant>(Add->getOperand(0)))
|
|
return getAddExpr(getMulExpr(LHSC, Add->getOperand(0)),
|
|
getMulExpr(LHSC, Add->getOperand(1)));
|
|
|
|
|
|
++Idx;
|
|
while (SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
|
|
// We found two constants, fold them together!
|
|
ConstantInt *Fold = ConstantInt::get(LHSC->getValue()->getValue() *
|
|
RHSC->getValue()->getValue());
|
|
Ops[0] = getConstant(Fold);
|
|
Ops.erase(Ops.begin()+1); // Erase the folded element
|
|
if (Ops.size() == 1) return Ops[0];
|
|
LHSC = cast<SCEVConstant>(Ops[0]);
|
|
}
|
|
|
|
// If we are left with a constant one being multiplied, strip it off.
|
|
if (cast<SCEVConstant>(Ops[0])->getValue()->equalsInt(1)) {
|
|
Ops.erase(Ops.begin());
|
|
--Idx;
|
|
} else if (cast<SCEVConstant>(Ops[0])->getValue()->isZero()) {
|
|
// If we have a multiply of zero, it will always be zero.
|
|
return Ops[0];
|
|
}
|
|
}
|
|
|
|
// Skip over the add expression until we get to a multiply.
|
|
while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
|
|
++Idx;
|
|
|
|
if (Ops.size() == 1)
|
|
return Ops[0];
|
|
|
|
// If there are mul operands inline them all into this expression.
|
|
if (Idx < Ops.size()) {
|
|
bool DeletedMul = false;
|
|
while (SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[Idx])) {
|
|
// If we have an mul, expand the mul operands onto the end of the operands
|
|
// list.
|
|
Ops.insert(Ops.end(), Mul->op_begin(), Mul->op_end());
|
|
Ops.erase(Ops.begin()+Idx);
|
|
DeletedMul = true;
|
|
}
|
|
|
|
// If we deleted at least one mul, we added operands to the end of the list,
|
|
// and they are not necessarily sorted. Recurse to resort and resimplify
|
|
// any operands we just aquired.
|
|
if (DeletedMul)
|
|
return getMulExpr(Ops);
|
|
}
|
|
|
|
// If there are any add recurrences in the operands list, see if any other
|
|
// added values are loop invariant. If so, we can fold them into the
|
|
// recurrence.
|
|
while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
|
|
++Idx;
|
|
|
|
// Scan over all recurrences, trying to fold loop invariants into them.
|
|
for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
|
|
// Scan all of the other operands to this mul and add them to the vector if
|
|
// they are loop invariant w.r.t. the recurrence.
|
|
std::vector<SCEVHandle> LIOps;
|
|
SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
|
|
for (unsigned i = 0, e = Ops.size(); i != e; ++i)
|
|
if (Ops[i]->isLoopInvariant(AddRec->getLoop())) {
|
|
LIOps.push_back(Ops[i]);
|
|
Ops.erase(Ops.begin()+i);
|
|
--i; --e;
|
|
}
|
|
|
|
// If we found some loop invariants, fold them into the recurrence.
|
|
if (!LIOps.empty()) {
|
|
// NLI * LI * {Start,+,Step} --> NLI * {LI*Start,+,LI*Step}
|
|
std::vector<SCEVHandle> NewOps;
|
|
NewOps.reserve(AddRec->getNumOperands());
|
|
if (LIOps.size() == 1) {
|
|
SCEV *Scale = LIOps[0];
|
|
for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
|
|
NewOps.push_back(getMulExpr(Scale, AddRec->getOperand(i)));
|
|
} else {
|
|
for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
|
|
std::vector<SCEVHandle> MulOps(LIOps);
|
|
MulOps.push_back(AddRec->getOperand(i));
|
|
NewOps.push_back(getMulExpr(MulOps));
|
|
}
|
|
}
|
|
|
|
SCEVHandle NewRec = getAddRecExpr(NewOps, AddRec->getLoop());
|
|
|
|
// If all of the other operands were loop invariant, we are done.
|
|
if (Ops.size() == 1) return NewRec;
|
|
|
|
// Otherwise, multiply the folded AddRec by the non-liv parts.
|
|
for (unsigned i = 0;; ++i)
|
|
if (Ops[i] == AddRec) {
|
|
Ops[i] = NewRec;
|
|
break;
|
|
}
|
|
return getMulExpr(Ops);
|
|
}
|
|
|
|
// Okay, if there weren't any loop invariants to be folded, check to see if
|
|
// there are multiple AddRec's with the same loop induction variable being
|
|
// multiplied together. If so, we can fold them.
|
|
for (unsigned OtherIdx = Idx+1;
|
|
OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);++OtherIdx)
|
|
if (OtherIdx != Idx) {
|
|
SCEVAddRecExpr *OtherAddRec = cast<SCEVAddRecExpr>(Ops[OtherIdx]);
|
|
if (AddRec->getLoop() == OtherAddRec->getLoop()) {
|
|
// F * G --> {A,+,B} * {C,+,D} --> {A*C,+,F*D + G*B + B*D}
|
|
SCEVAddRecExpr *F = AddRec, *G = OtherAddRec;
|
|
SCEVHandle NewStart = getMulExpr(F->getStart(),
|
|
G->getStart());
|
|
SCEVHandle B = F->getStepRecurrence(*this);
|
|
SCEVHandle D = G->getStepRecurrence(*this);
|
|
SCEVHandle NewStep = getAddExpr(getMulExpr(F, D),
|
|
getMulExpr(G, B),
|
|
getMulExpr(B, D));
|
|
SCEVHandle NewAddRec = getAddRecExpr(NewStart, NewStep,
|
|
F->getLoop());
|
|
if (Ops.size() == 2) return NewAddRec;
|
|
|
|
Ops.erase(Ops.begin()+Idx);
|
|
Ops.erase(Ops.begin()+OtherIdx-1);
|
|
Ops.push_back(NewAddRec);
|
|
return getMulExpr(Ops);
|
|
}
|
|
}
|
|
|
|
// Otherwise couldn't fold anything into this recurrence. Move onto the
|
|
// next one.
|
|
}
|
|
|
|
// Okay, it looks like we really DO need an mul expr. Check to see if we
|
|
// already have one, otherwise create a new one.
|
|
std::vector<SCEV*> SCEVOps(Ops.begin(), Ops.end());
|
|
SCEVCommutativeExpr *&Result = (*SCEVCommExprs)[std::make_pair(scMulExpr,
|
|
SCEVOps)];
|
|
if (Result == 0)
|
|
Result = new SCEVMulExpr(Ops);
|
|
return Result;
|
|
}
|
|
|
|
SCEVHandle ScalarEvolution::getUDivExpr(const SCEVHandle &LHS, const SCEVHandle &RHS) {
|
|
if (SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
|
|
if (RHSC->getValue()->equalsInt(1))
|
|
return LHS; // X udiv 1 --> x
|
|
|
|
if (SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
|
|
Constant *LHSCV = LHSC->getValue();
|
|
Constant *RHSCV = RHSC->getValue();
|
|
return getUnknown(ConstantExpr::getUDiv(LHSCV, RHSCV));
|
|
}
|
|
}
|
|
|
|
// FIXME: implement folding of (X*4)/4 when we know X*4 doesn't overflow.
|
|
|
|
SCEVUDivExpr *&Result = (*SCEVUDivs)[std::make_pair(LHS, RHS)];
|
|
if (Result == 0) Result = new SCEVUDivExpr(LHS, RHS);
|
|
return Result;
|
|
}
|
|
|
|
|
|
/// SCEVAddRecExpr::get - Get a add recurrence expression for the
|
|
/// specified loop. Simplify the expression as much as possible.
|
|
SCEVHandle ScalarEvolution::getAddRecExpr(const SCEVHandle &Start,
|
|
const SCEVHandle &Step, const Loop *L) {
|
|
std::vector<SCEVHandle> Operands;
|
|
Operands.push_back(Start);
|
|
if (SCEVAddRecExpr *StepChrec = dyn_cast<SCEVAddRecExpr>(Step))
|
|
if (StepChrec->getLoop() == L) {
|
|
Operands.insert(Operands.end(), StepChrec->op_begin(),
|
|
StepChrec->op_end());
|
|
return getAddRecExpr(Operands, L);
|
|
}
|
|
|
|
Operands.push_back(Step);
|
|
return getAddRecExpr(Operands, L);
|
|
}
|
|
|
|
/// SCEVAddRecExpr::get - Get a add recurrence expression for the
|
|
/// specified loop. Simplify the expression as much as possible.
|
|
SCEVHandle ScalarEvolution::getAddRecExpr(std::vector<SCEVHandle> &Operands,
|
|
const Loop *L) {
|
|
if (Operands.size() == 1) return Operands[0];
|
|
|
|
if (Operands.back()->isZero()) {
|
|
Operands.pop_back();
|
|
return getAddRecExpr(Operands, L); // {X,+,0} --> X
|
|
}
|
|
|
|
// Canonicalize nested AddRecs in by nesting them in order of loop depth.
|
|
if (SCEVAddRecExpr *NestedAR = dyn_cast<SCEVAddRecExpr>(Operands[0])) {
|
|
const Loop* NestedLoop = NestedAR->getLoop();
|
|
if (L->getLoopDepth() < NestedLoop->getLoopDepth()) {
|
|
std::vector<SCEVHandle> NestedOperands(NestedAR->op_begin(),
|
|
NestedAR->op_end());
|
|
SCEVHandle NestedARHandle(NestedAR);
|
|
Operands[0] = NestedAR->getStart();
|
|
NestedOperands[0] = getAddRecExpr(Operands, L);
|
|
return getAddRecExpr(NestedOperands, NestedLoop);
|
|
}
|
|
}
|
|
|
|
SCEVAddRecExpr *&Result =
|
|
(*SCEVAddRecExprs)[std::make_pair(L, std::vector<SCEV*>(Operands.begin(),
|
|
Operands.end()))];
|
|
if (Result == 0) Result = new SCEVAddRecExpr(Operands, L);
|
|
return Result;
|
|
}
|
|
|
|
SCEVHandle ScalarEvolution::getSMaxExpr(const SCEVHandle &LHS,
|
|
const SCEVHandle &RHS) {
|
|
std::vector<SCEVHandle> Ops;
|
|
Ops.push_back(LHS);
|
|
Ops.push_back(RHS);
|
|
return getSMaxExpr(Ops);
|
|
}
|
|
|
|
SCEVHandle ScalarEvolution::getSMaxExpr(std::vector<SCEVHandle> Ops) {
|
|
assert(!Ops.empty() && "Cannot get empty smax!");
|
|
if (Ops.size() == 1) return Ops[0];
|
|
|
|
// Sort by complexity, this groups all similar expression types together.
|
|
GroupByComplexity(Ops);
|
|
|
|
// If there are any constants, fold them together.
|
|
unsigned Idx = 0;
|
|
if (SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
|
|
++Idx;
|
|
assert(Idx < Ops.size());
|
|
while (SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
|
|
// We found two constants, fold them together!
|
|
ConstantInt *Fold = ConstantInt::get(
|
|
APIntOps::smax(LHSC->getValue()->getValue(),
|
|
RHSC->getValue()->getValue()));
|
|
Ops[0] = getConstant(Fold);
|
|
Ops.erase(Ops.begin()+1); // Erase the folded element
|
|
if (Ops.size() == 1) return Ops[0];
|
|
LHSC = cast<SCEVConstant>(Ops[0]);
|
|
}
|
|
|
|
// If we are left with a constant -inf, strip it off.
|
|
if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(true)) {
|
|
Ops.erase(Ops.begin());
|
|
--Idx;
|
|
}
|
|
}
|
|
|
|
if (Ops.size() == 1) return Ops[0];
|
|
|
|
// Find the first SMax
|
|
while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scSMaxExpr)
|
|
++Idx;
|
|
|
|
// Check to see if one of the operands is an SMax. If so, expand its operands
|
|
// onto our operand list, and recurse to simplify.
|
|
if (Idx < Ops.size()) {
|
|
bool DeletedSMax = false;
|
|
while (SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(Ops[Idx])) {
|
|
Ops.insert(Ops.end(), SMax->op_begin(), SMax->op_end());
|
|
Ops.erase(Ops.begin()+Idx);
|
|
DeletedSMax = true;
|
|
}
|
|
|
|
if (DeletedSMax)
|
|
return getSMaxExpr(Ops);
|
|
}
|
|
|
|
// Okay, check to see if the same value occurs in the operand list twice. If
|
|
// so, delete one. Since we sorted the list, these values are required to
|
|
// be adjacent.
|
|
for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
|
|
if (Ops[i] == Ops[i+1]) { // X smax Y smax Y --> X smax Y
|
|
Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
|
|
--i; --e;
|
|
}
|
|
|
|
if (Ops.size() == 1) return Ops[0];
|
|
|
|
assert(!Ops.empty() && "Reduced smax down to nothing!");
|
|
|
|
// Okay, it looks like we really DO need an smax expr. Check to see if we
|
|
// already have one, otherwise create a new one.
|
|
std::vector<SCEV*> SCEVOps(Ops.begin(), Ops.end());
|
|
SCEVCommutativeExpr *&Result = (*SCEVCommExprs)[std::make_pair(scSMaxExpr,
|
|
SCEVOps)];
|
|
if (Result == 0) Result = new SCEVSMaxExpr(Ops);
|
|
return Result;
|
|
}
|
|
|
|
SCEVHandle ScalarEvolution::getUMaxExpr(const SCEVHandle &LHS,
|
|
const SCEVHandle &RHS) {
|
|
std::vector<SCEVHandle> Ops;
|
|
Ops.push_back(LHS);
|
|
Ops.push_back(RHS);
|
|
return getUMaxExpr(Ops);
|
|
}
|
|
|
|
SCEVHandle ScalarEvolution::getUMaxExpr(std::vector<SCEVHandle> Ops) {
|
|
assert(!Ops.empty() && "Cannot get empty umax!");
|
|
if (Ops.size() == 1) return Ops[0];
|
|
|
|
// Sort by complexity, this groups all similar expression types together.
|
|
GroupByComplexity(Ops);
|
|
|
|
// If there are any constants, fold them together.
|
|
unsigned Idx = 0;
|
|
if (SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
|
|
++Idx;
|
|
assert(Idx < Ops.size());
|
|
while (SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
|
|
// We found two constants, fold them together!
|
|
ConstantInt *Fold = ConstantInt::get(
|
|
APIntOps::umax(LHSC->getValue()->getValue(),
|
|
RHSC->getValue()->getValue()));
|
|
Ops[0] = getConstant(Fold);
|
|
Ops.erase(Ops.begin()+1); // Erase the folded element
|
|
if (Ops.size() == 1) return Ops[0];
|
|
LHSC = cast<SCEVConstant>(Ops[0]);
|
|
}
|
|
|
|
// If we are left with a constant zero, strip it off.
|
|
if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(false)) {
|
|
Ops.erase(Ops.begin());
|
|
--Idx;
|
|
}
|
|
}
|
|
|
|
if (Ops.size() == 1) return Ops[0];
|
|
|
|
// Find the first UMax
|
|
while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scUMaxExpr)
|
|
++Idx;
|
|
|
|
// Check to see if one of the operands is a UMax. If so, expand its operands
|
|
// onto our operand list, and recurse to simplify.
|
|
if (Idx < Ops.size()) {
|
|
bool DeletedUMax = false;
|
|
while (SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(Ops[Idx])) {
|
|
Ops.insert(Ops.end(), UMax->op_begin(), UMax->op_end());
|
|
Ops.erase(Ops.begin()+Idx);
|
|
DeletedUMax = true;
|
|
}
|
|
|
|
if (DeletedUMax)
|
|
return getUMaxExpr(Ops);
|
|
}
|
|
|
|
// Okay, check to see if the same value occurs in the operand list twice. If
|
|
// so, delete one. Since we sorted the list, these values are required to
|
|
// be adjacent.
|
|
for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
|
|
if (Ops[i] == Ops[i+1]) { // X umax Y umax Y --> X umax Y
|
|
Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
|
|
--i; --e;
|
|
}
|
|
|
|
if (Ops.size() == 1) return Ops[0];
|
|
|
|
assert(!Ops.empty() && "Reduced umax down to nothing!");
|
|
|
|
// Okay, it looks like we really DO need a umax expr. Check to see if we
|
|
// already have one, otherwise create a new one.
|
|
std::vector<SCEV*> SCEVOps(Ops.begin(), Ops.end());
|
|
SCEVCommutativeExpr *&Result = (*SCEVCommExprs)[std::make_pair(scUMaxExpr,
|
|
SCEVOps)];
|
|
if (Result == 0) Result = new SCEVUMaxExpr(Ops);
|
|
return Result;
|
|
}
|
|
|
|
SCEVHandle ScalarEvolution::getUnknown(Value *V) {
|
|
if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
|
|
return getConstant(CI);
|
|
SCEVUnknown *&Result = (*SCEVUnknowns)[V];
|
|
if (Result == 0) Result = new SCEVUnknown(V);
|
|
return Result;
|
|
}
|
|
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// ScalarEvolutionsImpl Definition and Implementation
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
/// ScalarEvolutionsImpl - This class implements the main driver for the scalar
|
|
/// evolution code.
|
|
///
|
|
namespace {
|
|
struct VISIBILITY_HIDDEN ScalarEvolutionsImpl {
|
|
/// SE - A reference to the public ScalarEvolution object.
|
|
ScalarEvolution &SE;
|
|
|
|
/// F - The function we are analyzing.
|
|
///
|
|
Function &F;
|
|
|
|
/// LI - The loop information for the function we are currently analyzing.
|
|
///
|
|
LoopInfo &LI;
|
|
|
|
/// UnknownValue - This SCEV is used to represent unknown trip counts and
|
|
/// things.
|
|
SCEVHandle UnknownValue;
|
|
|
|
/// Scalars - This is a cache of the scalars we have analyzed so far.
|
|
///
|
|
std::map<Value*, SCEVHandle> Scalars;
|
|
|
|
/// BackedgeTakenCounts - Cache the backedge-taken count of the loops for
|
|
/// this function as they are computed.
|
|
std::map<const Loop*, SCEVHandle> BackedgeTakenCounts;
|
|
|
|
/// ConstantEvolutionLoopExitValue - This map contains entries for all of
|
|
/// the PHI instructions that we attempt to compute constant evolutions for.
|
|
/// This allows us to avoid potentially expensive recomputation of these
|
|
/// properties. An instruction maps to null if we are unable to compute its
|
|
/// exit value.
|
|
std::map<PHINode*, Constant*> ConstantEvolutionLoopExitValue;
|
|
|
|
public:
|
|
ScalarEvolutionsImpl(ScalarEvolution &se, Function &f, LoopInfo &li)
|
|
: SE(se), F(f), LI(li), UnknownValue(new SCEVCouldNotCompute()) {}
|
|
|
|
/// getSCEV - Return an existing SCEV if it exists, otherwise analyze the
|
|
/// expression and create a new one.
|
|
SCEVHandle getSCEV(Value *V);
|
|
|
|
/// hasSCEV - Return true if the SCEV for this value has already been
|
|
/// computed.
|
|
bool hasSCEV(Value *V) const {
|
|
return Scalars.count(V);
|
|
}
|
|
|
|
/// setSCEV - Insert the specified SCEV into the map of current SCEVs for
|
|
/// the specified value.
|
|
void setSCEV(Value *V, const SCEVHandle &H) {
|
|
bool isNew = Scalars.insert(std::make_pair(V, H)).second;
|
|
assert(isNew && "This entry already existed!");
|
|
isNew = false;
|
|
}
|
|
|
|
|
|
/// getSCEVAtScope - Compute the value of the specified expression within
|
|
/// the indicated loop (which may be null to indicate in no loop). If the
|
|
/// expression cannot be evaluated, return UnknownValue itself.
|
|
SCEVHandle getSCEVAtScope(SCEV *V, const Loop *L);
|
|
|
|
|
|
/// isLoopGuardedByCond - Test whether entry to the loop is protected by
|
|
/// a conditional between LHS and RHS.
|
|
bool isLoopGuardedByCond(const Loop *L, ICmpInst::Predicate Pred,
|
|
SCEV *LHS, SCEV *RHS);
|
|
|
|
/// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop
|
|
/// has an analyzable loop-invariant backedge-taken count.
|
|
bool hasLoopInvariantBackedgeTakenCount(const Loop *L);
|
|
|
|
/// forgetLoopBackedgeTakenCount - This method should be called by the
|
|
/// client when it has changed a loop in a way that may effect
|
|
/// ScalarEvolution's ability to compute a trip count, or if the loop
|
|
/// is deleted.
|
|
void forgetLoopBackedgeTakenCount(const Loop *L);
|
|
|
|
/// getBackedgeTakenCount - If the specified loop has a predictable
|
|
/// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute
|
|
/// object. The backedge-taken count is the number of times the loop header
|
|
/// will be branched to from within the loop. This is one less than the
|
|
/// trip count of the loop, since it doesn't count the first iteration,
|
|
/// when the header is branched to from outside the loop.
|
|
///
|
|
/// Note that it is not valid to call this method on a loop without a
|
|
/// loop-invariant backedge-taken count (see
|
|
/// hasLoopInvariantBackedgeTakenCount).
|
|
///
|
|
SCEVHandle getBackedgeTakenCount(const Loop *L);
|
|
|
|
/// deleteValueFromRecords - This method should be called by the
|
|
/// client before it removes a value from the program, to make sure
|
|
/// that no dangling references are left around.
|
|
void deleteValueFromRecords(Value *V);
|
|
|
|
private:
|
|
/// createSCEV - We know that there is no SCEV for the specified value.
|
|
/// Analyze the expression.
|
|
SCEVHandle createSCEV(Value *V);
|
|
|
|
/// createNodeForPHI - Provide the special handling we need to analyze PHI
|
|
/// SCEVs.
|
|
SCEVHandle createNodeForPHI(PHINode *PN);
|
|
|
|
/// ReplaceSymbolicValueWithConcrete - This looks up the computed SCEV value
|
|
/// for the specified instruction and replaces any references to the
|
|
/// symbolic value SymName with the specified value. This is used during
|
|
/// PHI resolution.
|
|
void ReplaceSymbolicValueWithConcrete(Instruction *I,
|
|
const SCEVHandle &SymName,
|
|
const SCEVHandle &NewVal);
|
|
|
|
/// ComputeBackedgeTakenCount - Compute the number of times the specified
|
|
/// loop will iterate.
|
|
SCEVHandle ComputeBackedgeTakenCount(const Loop *L);
|
|
|
|
/// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition
|
|
/// of 'icmp op load X, cst', try to see if we can compute the trip count.
|
|
SCEVHandle
|
|
ComputeLoadConstantCompareBackedgeTakenCount(LoadInst *LI,
|
|
Constant *RHS,
|
|
const Loop *L,
|
|
ICmpInst::Predicate p);
|
|
|
|
/// ComputeBackedgeTakenCountExhaustively - If the trip is known to execute
|
|
/// a constant number of times (the condition evolves only from constants),
|
|
/// try to evaluate a few iterations of the loop until we get the exit
|
|
/// condition gets a value of ExitWhen (true or false). If we cannot
|
|
/// evaluate the trip count of the loop, return UnknownValue.
|
|
SCEVHandle ComputeBackedgeTakenCountExhaustively(const Loop *L, Value *Cond,
|
|
bool ExitWhen);
|
|
|
|
/// HowFarToZero - Return the number of times a backedge comparing the
|
|
/// specified value to zero will execute. If not computable, return
|
|
/// UnknownValue.
|
|
SCEVHandle HowFarToZero(SCEV *V, const Loop *L);
|
|
|
|
/// HowFarToNonZero - Return the number of times a backedge checking the
|
|
/// specified value for nonzero will execute. If not computable, return
|
|
/// UnknownValue.
|
|
SCEVHandle HowFarToNonZero(SCEV *V, const Loop *L);
|
|
|
|
/// HowManyLessThans - Return the number of times a backedge containing the
|
|
/// specified less-than comparison will execute. If not computable, return
|
|
/// UnknownValue. isSigned specifies whether the less-than is signed.
|
|
SCEVHandle HowManyLessThans(SCEV *LHS, SCEV *RHS, const Loop *L,
|
|
bool isSigned);
|
|
|
|
/// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB
|
|
/// (which may not be an immediate predecessor) which has exactly one
|
|
/// successor from which BB is reachable, or null if no such block is
|
|
/// found.
|
|
BasicBlock* getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB);
|
|
|
|
/// getConstantEvolutionLoopExitValue - If we know that the specified Phi is
|
|
/// in the header of its containing loop, we know the loop executes a
|
|
/// constant number of times, and the PHI node is just a recurrence
|
|
/// involving constants, fold it.
|
|
Constant *getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& BEs,
|
|
const Loop *L);
|
|
};
|
|
}
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// Basic SCEV Analysis and PHI Idiom Recognition Code
|
|
//
|
|
|
|
/// deleteValueFromRecords - This method should be called by the
|
|
/// client before it removes an instruction from the program, to make sure
|
|
/// that no dangling references are left around.
|
|
void ScalarEvolutionsImpl::deleteValueFromRecords(Value *V) {
|
|
SmallVector<Value *, 16> Worklist;
|
|
|
|
if (Scalars.erase(V)) {
|
|
if (PHINode *PN = dyn_cast<PHINode>(V))
|
|
ConstantEvolutionLoopExitValue.erase(PN);
|
|
Worklist.push_back(V);
|
|
}
|
|
|
|
while (!Worklist.empty()) {
|
|
Value *VV = Worklist.back();
|
|
Worklist.pop_back();
|
|
|
|
for (Instruction::use_iterator UI = VV->use_begin(), UE = VV->use_end();
|
|
UI != UE; ++UI) {
|
|
Instruction *Inst = cast<Instruction>(*UI);
|
|
if (Scalars.erase(Inst)) {
|
|
if (PHINode *PN = dyn_cast<PHINode>(VV))
|
|
ConstantEvolutionLoopExitValue.erase(PN);
|
|
Worklist.push_back(Inst);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
/// getSCEV - Return an existing SCEV if it exists, otherwise analyze the
|
|
/// expression and create a new one.
|
|
SCEVHandle ScalarEvolutionsImpl::getSCEV(Value *V) {
|
|
assert(V->getType() != Type::VoidTy && "Can't analyze void expressions!");
|
|
|
|
std::map<Value*, SCEVHandle>::iterator I = Scalars.find(V);
|
|
if (I != Scalars.end()) return I->second;
|
|
SCEVHandle S = createSCEV(V);
|
|
Scalars.insert(std::make_pair(V, S));
|
|
return S;
|
|
}
|
|
|
|
/// ReplaceSymbolicValueWithConcrete - This looks up the computed SCEV value for
|
|
/// the specified instruction and replaces any references to the symbolic value
|
|
/// SymName with the specified value. This is used during PHI resolution.
|
|
void ScalarEvolutionsImpl::
|
|
ReplaceSymbolicValueWithConcrete(Instruction *I, const SCEVHandle &SymName,
|
|
const SCEVHandle &NewVal) {
|
|
std::map<Value*, SCEVHandle>::iterator SI = Scalars.find(I);
|
|
if (SI == Scalars.end()) return;
|
|
|
|
SCEVHandle NV =
|
|
SI->second->replaceSymbolicValuesWithConcrete(SymName, NewVal, SE);
|
|
if (NV == SI->second) return; // No change.
|
|
|
|
SI->second = NV; // Update the scalars map!
|
|
|
|
// Any instruction values that use this instruction might also need to be
|
|
// updated!
|
|
for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
|
|
UI != E; ++UI)
|
|
ReplaceSymbolicValueWithConcrete(cast<Instruction>(*UI), SymName, NewVal);
|
|
}
|
|
|
|
/// createNodeForPHI - PHI nodes have two cases. Either the PHI node exists in
|
|
/// a loop header, making it a potential recurrence, or it doesn't.
|
|
///
|
|
SCEVHandle ScalarEvolutionsImpl::createNodeForPHI(PHINode *PN) {
|
|
if (PN->getNumIncomingValues() == 2) // The loops have been canonicalized.
|
|
if (const Loop *L = LI.getLoopFor(PN->getParent()))
|
|
if (L->getHeader() == PN->getParent()) {
|
|
// If it lives in the loop header, it has two incoming values, one
|
|
// from outside the loop, and one from inside.
|
|
unsigned IncomingEdge = L->contains(PN->getIncomingBlock(0));
|
|
unsigned BackEdge = IncomingEdge^1;
|
|
|
|
// While we are analyzing this PHI node, handle its value symbolically.
|
|
SCEVHandle SymbolicName = SE.getUnknown(PN);
|
|
assert(Scalars.find(PN) == Scalars.end() &&
|
|
"PHI node already processed?");
|
|
Scalars.insert(std::make_pair(PN, SymbolicName));
|
|
|
|
// Using this symbolic name for the PHI, analyze the value coming around
|
|
// the back-edge.
|
|
SCEVHandle BEValue = getSCEV(PN->getIncomingValue(BackEdge));
|
|
|
|
// NOTE: If BEValue is loop invariant, we know that the PHI node just
|
|
// has a special value for the first iteration of the loop.
|
|
|
|
// If the value coming around the backedge is an add with the symbolic
|
|
// value we just inserted, then we found a simple induction variable!
|
|
if (SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(BEValue)) {
|
|
// If there is a single occurrence of the symbolic value, replace it
|
|
// with a recurrence.
|
|
unsigned FoundIndex = Add->getNumOperands();
|
|
for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
|
|
if (Add->getOperand(i) == SymbolicName)
|
|
if (FoundIndex == e) {
|
|
FoundIndex = i;
|
|
break;
|
|
}
|
|
|
|
if (FoundIndex != Add->getNumOperands()) {
|
|
// Create an add with everything but the specified operand.
|
|
std::vector<SCEVHandle> Ops;
|
|
for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
|
|
if (i != FoundIndex)
|
|
Ops.push_back(Add->getOperand(i));
|
|
SCEVHandle Accum = SE.getAddExpr(Ops);
|
|
|
|
// This is not a valid addrec if the step amount is varying each
|
|
// loop iteration, but is not itself an addrec in this loop.
|
|
if (Accum->isLoopInvariant(L) ||
|
|
(isa<SCEVAddRecExpr>(Accum) &&
|
|
cast<SCEVAddRecExpr>(Accum)->getLoop() == L)) {
|
|
SCEVHandle StartVal = getSCEV(PN->getIncomingValue(IncomingEdge));
|
|
SCEVHandle PHISCEV = SE.getAddRecExpr(StartVal, Accum, L);
|
|
|
|
// Okay, for the entire analysis of this edge we assumed the PHI
|
|
// to be symbolic. We now need to go back and update all of the
|
|
// entries for the scalars that use the PHI (except for the PHI
|
|
// itself) to use the new analyzed value instead of the "symbolic"
|
|
// value.
|
|
ReplaceSymbolicValueWithConcrete(PN, SymbolicName, PHISCEV);
|
|
return PHISCEV;
|
|
}
|
|
}
|
|
} else if (SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(BEValue)) {
|
|
// Otherwise, this could be a loop like this:
|
|
// i = 0; for (j = 1; ..; ++j) { .... i = j; }
|
|
// In this case, j = {1,+,1} and BEValue is j.
|
|
// Because the other in-value of i (0) fits the evolution of BEValue
|
|
// i really is an addrec evolution.
|
|
if (AddRec->getLoop() == L && AddRec->isAffine()) {
|
|
SCEVHandle StartVal = getSCEV(PN->getIncomingValue(IncomingEdge));
|
|
|
|
// If StartVal = j.start - j.stride, we can use StartVal as the
|
|
// initial step of the addrec evolution.
|
|
if (StartVal == SE.getMinusSCEV(AddRec->getOperand(0),
|
|
AddRec->getOperand(1))) {
|
|
SCEVHandle PHISCEV =
|
|
SE.getAddRecExpr(StartVal, AddRec->getOperand(1), L);
|
|
|
|
// Okay, for the entire analysis of this edge we assumed the PHI
|
|
// to be symbolic. We now need to go back and update all of the
|
|
// entries for the scalars that use the PHI (except for the PHI
|
|
// itself) to use the new analyzed value instead of the "symbolic"
|
|
// value.
|
|
ReplaceSymbolicValueWithConcrete(PN, SymbolicName, PHISCEV);
|
|
return PHISCEV;
|
|
}
|
|
}
|
|
}
|
|
|
|
return SymbolicName;
|
|
}
|
|
|
|
// If it's not a loop phi, we can't handle it yet.
|
|
return SE.getUnknown(PN);
|
|
}
|
|
|
|
/// GetMinTrailingZeros - Determine the minimum number of zero bits that S is
|
|
/// guaranteed to end in (at every loop iteration). It is, at the same time,
|
|
/// the minimum number of times S is divisible by 2. For example, given {4,+,8}
|
|
/// it returns 2. If S is guaranteed to be 0, it returns the bitwidth of S.
|
|
static uint32_t GetMinTrailingZeros(SCEVHandle S) {
|
|
if (SCEVConstant *C = dyn_cast<SCEVConstant>(S))
|
|
return C->getValue()->getValue().countTrailingZeros();
|
|
|
|
if (SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(S))
|
|
return std::min(GetMinTrailingZeros(T->getOperand()), T->getBitWidth());
|
|
|
|
if (SCEVZeroExtendExpr *E = dyn_cast<SCEVZeroExtendExpr>(S)) {
|
|
uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
|
|
return OpRes == E->getOperand()->getBitWidth() ? E->getBitWidth() : OpRes;
|
|
}
|
|
|
|
if (SCEVSignExtendExpr *E = dyn_cast<SCEVSignExtendExpr>(S)) {
|
|
uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
|
|
return OpRes == E->getOperand()->getBitWidth() ? E->getBitWidth() : OpRes;
|
|
}
|
|
|
|
if (SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(S)) {
|
|
// The result is the min of all operands results.
|
|
uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
|
|
for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
|
|
MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
|
|
return MinOpRes;
|
|
}
|
|
|
|
if (SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S)) {
|
|
// The result is the sum of all operands results.
|
|
uint32_t SumOpRes = GetMinTrailingZeros(M->getOperand(0));
|
|
uint32_t BitWidth = M->getBitWidth();
|
|
for (unsigned i = 1, e = M->getNumOperands();
|
|
SumOpRes != BitWidth && i != e; ++i)
|
|
SumOpRes = std::min(SumOpRes + GetMinTrailingZeros(M->getOperand(i)),
|
|
BitWidth);
|
|
return SumOpRes;
|
|
}
|
|
|
|
if (SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) {
|
|
// The result is the min of all operands results.
|
|
uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
|
|
for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
|
|
MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
|
|
return MinOpRes;
|
|
}
|
|
|
|
if (SCEVSMaxExpr *M = dyn_cast<SCEVSMaxExpr>(S)) {
|
|
// The result is the min of all operands results.
|
|
uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
|
|
for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
|
|
MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
|
|
return MinOpRes;
|
|
}
|
|
|
|
if (SCEVUMaxExpr *M = dyn_cast<SCEVUMaxExpr>(S)) {
|
|
// The result is the min of all operands results.
|
|
uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
|
|
for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
|
|
MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
|
|
return MinOpRes;
|
|
}
|
|
|
|
// SCEVUDivExpr, SCEVUnknown
|
|
return 0;
|
|
}
|
|
|
|
/// createSCEV - We know that there is no SCEV for the specified value.
|
|
/// Analyze the expression.
|
|
///
|
|
SCEVHandle ScalarEvolutionsImpl::createSCEV(Value *V) {
|
|
if (!isa<IntegerType>(V->getType()))
|
|
return SE.getUnknown(V);
|
|
|
|
unsigned Opcode = Instruction::UserOp1;
|
|
if (Instruction *I = dyn_cast<Instruction>(V))
|
|
Opcode = I->getOpcode();
|
|
else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
|
|
Opcode = CE->getOpcode();
|
|
else
|
|
return SE.getUnknown(V);
|
|
|
|
User *U = cast<User>(V);
|
|
switch (Opcode) {
|
|
case Instruction::Add:
|
|
return SE.getAddExpr(getSCEV(U->getOperand(0)),
|
|
getSCEV(U->getOperand(1)));
|
|
case Instruction::Mul:
|
|
return SE.getMulExpr(getSCEV(U->getOperand(0)),
|
|
getSCEV(U->getOperand(1)));
|
|
case Instruction::UDiv:
|
|
return SE.getUDivExpr(getSCEV(U->getOperand(0)),
|
|
getSCEV(U->getOperand(1)));
|
|
case Instruction::Sub:
|
|
return SE.getMinusSCEV(getSCEV(U->getOperand(0)),
|
|
getSCEV(U->getOperand(1)));
|
|
case Instruction::Or:
|
|
// If the RHS of the Or is a constant, we may have something like:
|
|
// X*4+1 which got turned into X*4|1. Handle this as an Add so loop
|
|
// optimizations will transparently handle this case.
|
|
//
|
|
// In order for this transformation to be safe, the LHS must be of the
|
|
// form X*(2^n) and the Or constant must be less than 2^n.
|
|
if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
|
|
SCEVHandle LHS = getSCEV(U->getOperand(0));
|
|
const APInt &CIVal = CI->getValue();
|
|
if (GetMinTrailingZeros(LHS) >=
|
|
(CIVal.getBitWidth() - CIVal.countLeadingZeros()))
|
|
return SE.getAddExpr(LHS, getSCEV(U->getOperand(1)));
|
|
}
|
|
break;
|
|
case Instruction::Xor:
|
|
if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
|
|
// If the RHS of the xor is a signbit, then this is just an add.
|
|
// Instcombine turns add of signbit into xor as a strength reduction step.
|
|
if (CI->getValue().isSignBit())
|
|
return SE.getAddExpr(getSCEV(U->getOperand(0)),
|
|
getSCEV(U->getOperand(1)));
|
|
|
|
// If the RHS of xor is -1, then this is a not operation.
|
|
else if (CI->isAllOnesValue())
|
|
return SE.getNotSCEV(getSCEV(U->getOperand(0)));
|
|
}
|
|
break;
|
|
|
|
case Instruction::Shl:
|
|
// Turn shift left of a constant amount into a multiply.
|
|
if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
|
|
uint32_t BitWidth = cast<IntegerType>(V->getType())->getBitWidth();
|
|
Constant *X = ConstantInt::get(
|
|
APInt(BitWidth, 1).shl(SA->getLimitedValue(BitWidth)));
|
|
return SE.getMulExpr(getSCEV(U->getOperand(0)), getSCEV(X));
|
|
}
|
|
break;
|
|
|
|
case Instruction::LShr:
|
|
// Turn logical shift right of a constant into a unsigned divide.
|
|
if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
|
|
uint32_t BitWidth = cast<IntegerType>(V->getType())->getBitWidth();
|
|
Constant *X = ConstantInt::get(
|
|
APInt(BitWidth, 1).shl(SA->getLimitedValue(BitWidth)));
|
|
return SE.getUDivExpr(getSCEV(U->getOperand(0)), getSCEV(X));
|
|
}
|
|
break;
|
|
|
|
case Instruction::Trunc:
|
|
return SE.getTruncateExpr(getSCEV(U->getOperand(0)), U->getType());
|
|
|
|
case Instruction::ZExt:
|
|
return SE.getZeroExtendExpr(getSCEV(U->getOperand(0)), U->getType());
|
|
|
|
case Instruction::SExt:
|
|
return SE.getSignExtendExpr(getSCEV(U->getOperand(0)), U->getType());
|
|
|
|
case Instruction::BitCast:
|
|
// BitCasts are no-op casts so we just eliminate the cast.
|
|
if (U->getType()->isInteger() &&
|
|
U->getOperand(0)->getType()->isInteger())
|
|
return getSCEV(U->getOperand(0));
|
|
break;
|
|
|
|
case Instruction::PHI:
|
|
return createNodeForPHI(cast<PHINode>(U));
|
|
|
|
case Instruction::Select:
|
|
// This could be a smax or umax that was lowered earlier.
|
|
// Try to recover it.
|
|
if (ICmpInst *ICI = dyn_cast<ICmpInst>(U->getOperand(0))) {
|
|
Value *LHS = ICI->getOperand(0);
|
|
Value *RHS = ICI->getOperand(1);
|
|
switch (ICI->getPredicate()) {
|
|
case ICmpInst::ICMP_SLT:
|
|
case ICmpInst::ICMP_SLE:
|
|
std::swap(LHS, RHS);
|
|
// fall through
|
|
case ICmpInst::ICMP_SGT:
|
|
case ICmpInst::ICMP_SGE:
|
|
if (LHS == U->getOperand(1) && RHS == U->getOperand(2))
|
|
return SE.getSMaxExpr(getSCEV(LHS), getSCEV(RHS));
|
|
else if (LHS == U->getOperand(2) && RHS == U->getOperand(1))
|
|
// ~smax(~x, ~y) == smin(x, y).
|
|
return SE.getNotSCEV(SE.getSMaxExpr(
|
|
SE.getNotSCEV(getSCEV(LHS)),
|
|
SE.getNotSCEV(getSCEV(RHS))));
|
|
break;
|
|
case ICmpInst::ICMP_ULT:
|
|
case ICmpInst::ICMP_ULE:
|
|
std::swap(LHS, RHS);
|
|
// fall through
|
|
case ICmpInst::ICMP_UGT:
|
|
case ICmpInst::ICMP_UGE:
|
|
if (LHS == U->getOperand(1) && RHS == U->getOperand(2))
|
|
return SE.getUMaxExpr(getSCEV(LHS), getSCEV(RHS));
|
|
else if (LHS == U->getOperand(2) && RHS == U->getOperand(1))
|
|
// ~umax(~x, ~y) == umin(x, y)
|
|
return SE.getNotSCEV(SE.getUMaxExpr(SE.getNotSCEV(getSCEV(LHS)),
|
|
SE.getNotSCEV(getSCEV(RHS))));
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
|
|
default: // We cannot analyze this expression.
|
|
break;
|
|
}
|
|
|
|
return SE.getUnknown(V);
|
|
}
|
|
|
|
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// Iteration Count Computation Code
|
|
//
|
|
|
|
/// getBackedgeTakenCount - If the specified loop has a predictable
|
|
/// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute
|
|
/// object. The backedge-taken count is the number of times the loop header
|
|
/// will be branched to from within the loop. This is one less than the
|
|
/// trip count of the loop, since it doesn't count the first iteration,
|
|
/// when the header is branched to from outside the loop.
|
|
///
|
|
/// Note that it is not valid to call this method on a loop without a
|
|
/// loop-invariant backedge-taken count (see
|
|
/// hasLoopInvariantBackedgeTakenCount).
|
|
///
|
|
SCEVHandle ScalarEvolutionsImpl::getBackedgeTakenCount(const Loop *L) {
|
|
std::map<const Loop*, SCEVHandle>::iterator I = BackedgeTakenCounts.find(L);
|
|
if (I == BackedgeTakenCounts.end()) {
|
|
SCEVHandle ItCount = ComputeBackedgeTakenCount(L);
|
|
I = BackedgeTakenCounts.insert(std::make_pair(L, ItCount)).first;
|
|
if (ItCount != UnknownValue) {
|
|
assert(ItCount->isLoopInvariant(L) &&
|
|
"Computed trip count isn't loop invariant for loop!");
|
|
++NumTripCountsComputed;
|
|
} else if (isa<PHINode>(L->getHeader()->begin())) {
|
|
// Only count loops that have phi nodes as not being computable.
|
|
++NumTripCountsNotComputed;
|
|
}
|
|
}
|
|
return I->second;
|
|
}
|
|
|
|
/// forgetLoopBackedgeTakenCount - This method should be called by the
|
|
/// client when it has changed a loop in a way that may effect
|
|
/// ScalarEvolution's ability to compute a trip count, or if the loop
|
|
/// is deleted.
|
|
void ScalarEvolutionsImpl::forgetLoopBackedgeTakenCount(const Loop *L) {
|
|
BackedgeTakenCounts.erase(L);
|
|
}
|
|
|
|
/// ComputeBackedgeTakenCount - Compute the number of times the backedge
|
|
/// of the specified loop will execute.
|
|
SCEVHandle ScalarEvolutionsImpl::ComputeBackedgeTakenCount(const Loop *L) {
|
|
// If the loop has a non-one exit block count, we can't analyze it.
|
|
SmallVector<BasicBlock*, 8> ExitBlocks;
|
|
L->getExitBlocks(ExitBlocks);
|
|
if (ExitBlocks.size() != 1) return UnknownValue;
|
|
|
|
// Okay, there is one exit block. Try to find the condition that causes the
|
|
// loop to be exited.
|
|
BasicBlock *ExitBlock = ExitBlocks[0];
|
|
|
|
BasicBlock *ExitingBlock = 0;
|
|
for (pred_iterator PI = pred_begin(ExitBlock), E = pred_end(ExitBlock);
|
|
PI != E; ++PI)
|
|
if (L->contains(*PI)) {
|
|
if (ExitingBlock == 0)
|
|
ExitingBlock = *PI;
|
|
else
|
|
return UnknownValue; // More than one block exiting!
|
|
}
|
|
assert(ExitingBlock && "No exits from loop, something is broken!");
|
|
|
|
// Okay, we've computed the exiting block. See what condition causes us to
|
|
// exit.
|
|
//
|
|
// FIXME: we should be able to handle switch instructions (with a single exit)
|
|
BranchInst *ExitBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
|
|
if (ExitBr == 0) return UnknownValue;
|
|
assert(ExitBr->isConditional() && "If unconditional, it can't be in loop!");
|
|
|
|
// At this point, we know we have a conditional branch that determines whether
|
|
// the loop is exited. However, we don't know if the branch is executed each
|
|
// time through the loop. If not, then the execution count of the branch will
|
|
// not be equal to the trip count of the loop.
|
|
//
|
|
// Currently we check for this by checking to see if the Exit branch goes to
|
|
// the loop header. If so, we know it will always execute the same number of
|
|
// times as the loop. We also handle the case where the exit block *is* the
|
|
// loop header. This is common for un-rotated loops. More extensive analysis
|
|
// could be done to handle more cases here.
|
|
if (ExitBr->getSuccessor(0) != L->getHeader() &&
|
|
ExitBr->getSuccessor(1) != L->getHeader() &&
|
|
ExitBr->getParent() != L->getHeader())
|
|
return UnknownValue;
|
|
|
|
ICmpInst *ExitCond = dyn_cast<ICmpInst>(ExitBr->getCondition());
|
|
|
|
// If it's not an integer comparison then compute it the hard way.
|
|
// Note that ICmpInst deals with pointer comparisons too so we must check
|
|
// the type of the operand.
|
|
if (ExitCond == 0 || isa<PointerType>(ExitCond->getOperand(0)->getType()))
|
|
return ComputeBackedgeTakenCountExhaustively(L, ExitBr->getCondition(),
|
|
ExitBr->getSuccessor(0) == ExitBlock);
|
|
|
|
// If the condition was exit on true, convert the condition to exit on false
|
|
ICmpInst::Predicate Cond;
|
|
if (ExitBr->getSuccessor(1) == ExitBlock)
|
|
Cond = ExitCond->getPredicate();
|
|
else
|
|
Cond = ExitCond->getInversePredicate();
|
|
|
|
// Handle common loops like: for (X = "string"; *X; ++X)
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(ExitCond->getOperand(0)))
|
|
if (Constant *RHS = dyn_cast<Constant>(ExitCond->getOperand(1))) {
|
|
SCEVHandle ItCnt =
|
|
ComputeLoadConstantCompareBackedgeTakenCount(LI, RHS, L, Cond);
|
|
if (!isa<SCEVCouldNotCompute>(ItCnt)) return ItCnt;
|
|
}
|
|
|
|
SCEVHandle LHS = getSCEV(ExitCond->getOperand(0));
|
|
SCEVHandle RHS = getSCEV(ExitCond->getOperand(1));
|
|
|
|
// Try to evaluate any dependencies out of the loop.
|
|
SCEVHandle Tmp = getSCEVAtScope(LHS, L);
|
|
if (!isa<SCEVCouldNotCompute>(Tmp)) LHS = Tmp;
|
|
Tmp = getSCEVAtScope(RHS, L);
|
|
if (!isa<SCEVCouldNotCompute>(Tmp)) RHS = Tmp;
|
|
|
|
// At this point, we would like to compute how many iterations of the
|
|
// loop the predicate will return true for these inputs.
|
|
if (LHS->isLoopInvariant(L) && !RHS->isLoopInvariant(L)) {
|
|
// If there is a loop-invariant, force it into the RHS.
|
|
std::swap(LHS, RHS);
|
|
Cond = ICmpInst::getSwappedPredicate(Cond);
|
|
}
|
|
|
|
// FIXME: think about handling pointer comparisons! i.e.:
|
|
// while (P != P+100) ++P;
|
|
|
|
// If we have a comparison of a chrec against a constant, try to use value
|
|
// ranges to answer this query.
|
|
if (SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS))
|
|
if (SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS))
|
|
if (AddRec->getLoop() == L) {
|
|
// Form the comparison range using the constant of the correct type so
|
|
// that the ConstantRange class knows to do a signed or unsigned
|
|
// comparison.
|
|
ConstantInt *CompVal = RHSC->getValue();
|
|
const Type *RealTy = ExitCond->getOperand(0)->getType();
|
|
CompVal = dyn_cast<ConstantInt>(
|
|
ConstantExpr::getBitCast(CompVal, RealTy));
|
|
if (CompVal) {
|
|
// Form the constant range.
|
|
ConstantRange CompRange(
|
|
ICmpInst::makeConstantRange(Cond, CompVal->getValue()));
|
|
|
|
SCEVHandle Ret = AddRec->getNumIterationsInRange(CompRange, SE);
|
|
if (!isa<SCEVCouldNotCompute>(Ret)) return Ret;
|
|
}
|
|
}
|
|
|
|
switch (Cond) {
|
|
case ICmpInst::ICMP_NE: { // while (X != Y)
|
|
// Convert to: while (X-Y != 0)
|
|
SCEVHandle TC = HowFarToZero(SE.getMinusSCEV(LHS, RHS), L);
|
|
if (!isa<SCEVCouldNotCompute>(TC)) return TC;
|
|
break;
|
|
}
|
|
case ICmpInst::ICMP_EQ: {
|
|
// Convert to: while (X-Y == 0) // while (X == Y)
|
|
SCEVHandle TC = HowFarToNonZero(SE.getMinusSCEV(LHS, RHS), L);
|
|
if (!isa<SCEVCouldNotCompute>(TC)) return TC;
|
|
break;
|
|
}
|
|
case ICmpInst::ICMP_SLT: {
|
|
SCEVHandle TC = HowManyLessThans(LHS, RHS, L, true);
|
|
if (!isa<SCEVCouldNotCompute>(TC)) return TC;
|
|
break;
|
|
}
|
|
case ICmpInst::ICMP_SGT: {
|
|
SCEVHandle TC = HowManyLessThans(SE.getNotSCEV(LHS),
|
|
SE.getNotSCEV(RHS), L, true);
|
|
if (!isa<SCEVCouldNotCompute>(TC)) return TC;
|
|
break;
|
|
}
|
|
case ICmpInst::ICMP_ULT: {
|
|
SCEVHandle TC = HowManyLessThans(LHS, RHS, L, false);
|
|
if (!isa<SCEVCouldNotCompute>(TC)) return TC;
|
|
break;
|
|
}
|
|
case ICmpInst::ICMP_UGT: {
|
|
SCEVHandle TC = HowManyLessThans(SE.getNotSCEV(LHS),
|
|
SE.getNotSCEV(RHS), L, false);
|
|
if (!isa<SCEVCouldNotCompute>(TC)) return TC;
|
|
break;
|
|
}
|
|
default:
|
|
#if 0
|
|
cerr << "ComputeBackedgeTakenCount ";
|
|
if (ExitCond->getOperand(0)->getType()->isUnsigned())
|
|
cerr << "[unsigned] ";
|
|
cerr << *LHS << " "
|
|
<< Instruction::getOpcodeName(Instruction::ICmp)
|
|
<< " " << *RHS << "\n";
|
|
#endif
|
|
break;
|
|
}
|
|
return
|
|
ComputeBackedgeTakenCountExhaustively(L, ExitCond,
|
|
ExitBr->getSuccessor(0) == ExitBlock);
|
|
}
|
|
|
|
static ConstantInt *
|
|
EvaluateConstantChrecAtConstant(const SCEVAddRecExpr *AddRec, ConstantInt *C,
|
|
ScalarEvolution &SE) {
|
|
SCEVHandle InVal = SE.getConstant(C);
|
|
SCEVHandle Val = AddRec->evaluateAtIteration(InVal, SE);
|
|
assert(isa<SCEVConstant>(Val) &&
|
|
"Evaluation of SCEV at constant didn't fold correctly?");
|
|
return cast<SCEVConstant>(Val)->getValue();
|
|
}
|
|
|
|
/// GetAddressedElementFromGlobal - Given a global variable with an initializer
|
|
/// and a GEP expression (missing the pointer index) indexing into it, return
|
|
/// the addressed element of the initializer or null if the index expression is
|
|
/// invalid.
|
|
static Constant *
|
|
GetAddressedElementFromGlobal(GlobalVariable *GV,
|
|
const std::vector<ConstantInt*> &Indices) {
|
|
Constant *Init = GV->getInitializer();
|
|
for (unsigned i = 0, e = Indices.size(); i != e; ++i) {
|
|
uint64_t Idx = Indices[i]->getZExtValue();
|
|
if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) {
|
|
assert(Idx < CS->getNumOperands() && "Bad struct index!");
|
|
Init = cast<Constant>(CS->getOperand(Idx));
|
|
} else if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) {
|
|
if (Idx >= CA->getNumOperands()) return 0; // Bogus program
|
|
Init = cast<Constant>(CA->getOperand(Idx));
|
|
} else if (isa<ConstantAggregateZero>(Init)) {
|
|
if (const StructType *STy = dyn_cast<StructType>(Init->getType())) {
|
|
assert(Idx < STy->getNumElements() && "Bad struct index!");
|
|
Init = Constant::getNullValue(STy->getElementType(Idx));
|
|
} else if (const ArrayType *ATy = dyn_cast<ArrayType>(Init->getType())) {
|
|
if (Idx >= ATy->getNumElements()) return 0; // Bogus program
|
|
Init = Constant::getNullValue(ATy->getElementType());
|
|
} else {
|
|
assert(0 && "Unknown constant aggregate type!");
|
|
}
|
|
return 0;
|
|
} else {
|
|
return 0; // Unknown initializer type
|
|
}
|
|
}
|
|
return Init;
|
|
}
|
|
|
|
/// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition of
|
|
/// 'icmp op load X, cst', try to see if we can compute the backedge
|
|
/// execution count.
|
|
SCEVHandle ScalarEvolutionsImpl::
|
|
ComputeLoadConstantCompareBackedgeTakenCount(LoadInst *LI, Constant *RHS,
|
|
const Loop *L,
|
|
ICmpInst::Predicate predicate) {
|
|
if (LI->isVolatile()) return UnknownValue;
|
|
|
|
// Check to see if the loaded pointer is a getelementptr of a global.
|
|
GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(LI->getOperand(0));
|
|
if (!GEP) return UnknownValue;
|
|
|
|
// Make sure that it is really a constant global we are gepping, with an
|
|
// initializer, and make sure the first IDX is really 0.
|
|
GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
|
|
if (!GV || !GV->isConstant() || !GV->hasInitializer() ||
|
|
GEP->getNumOperands() < 3 || !isa<Constant>(GEP->getOperand(1)) ||
|
|
!cast<Constant>(GEP->getOperand(1))->isNullValue())
|
|
return UnknownValue;
|
|
|
|
// Okay, we allow one non-constant index into the GEP instruction.
|
|
Value *VarIdx = 0;
|
|
std::vector<ConstantInt*> Indexes;
|
|
unsigned VarIdxNum = 0;
|
|
for (unsigned i = 2, e = GEP->getNumOperands(); i != e; ++i)
|
|
if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) {
|
|
Indexes.push_back(CI);
|
|
} else if (!isa<ConstantInt>(GEP->getOperand(i))) {
|
|
if (VarIdx) return UnknownValue; // Multiple non-constant idx's.
|
|
VarIdx = GEP->getOperand(i);
|
|
VarIdxNum = i-2;
|
|
Indexes.push_back(0);
|
|
}
|
|
|
|
// Okay, we know we have a (load (gep GV, 0, X)) comparison with a constant.
|
|
// Check to see if X is a loop variant variable value now.
|
|
SCEVHandle Idx = getSCEV(VarIdx);
|
|
SCEVHandle Tmp = getSCEVAtScope(Idx, L);
|
|
if (!isa<SCEVCouldNotCompute>(Tmp)) Idx = Tmp;
|
|
|
|
// We can only recognize very limited forms of loop index expressions, in
|
|
// particular, only affine AddRec's like {C1,+,C2}.
|
|
SCEVAddRecExpr *IdxExpr = dyn_cast<SCEVAddRecExpr>(Idx);
|
|
if (!IdxExpr || !IdxExpr->isAffine() || IdxExpr->isLoopInvariant(L) ||
|
|
!isa<SCEVConstant>(IdxExpr->getOperand(0)) ||
|
|
!isa<SCEVConstant>(IdxExpr->getOperand(1)))
|
|
return UnknownValue;
|
|
|
|
unsigned MaxSteps = MaxBruteForceIterations;
|
|
for (unsigned IterationNum = 0; IterationNum != MaxSteps; ++IterationNum) {
|
|
ConstantInt *ItCst =
|
|
ConstantInt::get(IdxExpr->getType(), IterationNum);
|
|
ConstantInt *Val = EvaluateConstantChrecAtConstant(IdxExpr, ItCst, SE);
|
|
|
|
// Form the GEP offset.
|
|
Indexes[VarIdxNum] = Val;
|
|
|
|
Constant *Result = GetAddressedElementFromGlobal(GV, Indexes);
|
|
if (Result == 0) break; // Cannot compute!
|
|
|
|
// Evaluate the condition for this iteration.
|
|
Result = ConstantExpr::getICmp(predicate, Result, RHS);
|
|
if (!isa<ConstantInt>(Result)) break; // Couldn't decide for sure
|
|
if (cast<ConstantInt>(Result)->getValue().isMinValue()) {
|
|
#if 0
|
|
cerr << "\n***\n*** Computed loop count " << *ItCst
|
|
<< "\n*** From global " << *GV << "*** BB: " << *L->getHeader()
|
|
<< "***\n";
|
|
#endif
|
|
++NumArrayLenItCounts;
|
|
return SE.getConstant(ItCst); // Found terminating iteration!
|
|
}
|
|
}
|
|
return UnknownValue;
|
|
}
|
|
|
|
|
|
/// CanConstantFold - Return true if we can constant fold an instruction of the
|
|
/// specified type, assuming that all operands were constants.
|
|
static bool CanConstantFold(const Instruction *I) {
|
|
if (isa<BinaryOperator>(I) || isa<CmpInst>(I) ||
|
|
isa<SelectInst>(I) || isa<CastInst>(I) || isa<GetElementPtrInst>(I))
|
|
return true;
|
|
|
|
if (const CallInst *CI = dyn_cast<CallInst>(I))
|
|
if (const Function *F = CI->getCalledFunction())
|
|
return canConstantFoldCallTo(F);
|
|
return false;
|
|
}
|
|
|
|
/// getConstantEvolvingPHI - Given an LLVM value and a loop, return a PHI node
|
|
/// in the loop that V is derived from. We allow arbitrary operations along the
|
|
/// way, but the operands of an operation must either be constants or a value
|
|
/// derived from a constant PHI. If this expression does not fit with these
|
|
/// constraints, return null.
|
|
static PHINode *getConstantEvolvingPHI(Value *V, const Loop *L) {
|
|
// If this is not an instruction, or if this is an instruction outside of the
|
|
// loop, it can't be derived from a loop PHI.
|
|
Instruction *I = dyn_cast<Instruction>(V);
|
|
if (I == 0 || !L->contains(I->getParent())) return 0;
|
|
|
|
if (PHINode *PN = dyn_cast<PHINode>(I)) {
|
|
if (L->getHeader() == I->getParent())
|
|
return PN;
|
|
else
|
|
// We don't currently keep track of the control flow needed to evaluate
|
|
// PHIs, so we cannot handle PHIs inside of loops.
|
|
return 0;
|
|
}
|
|
|
|
// If we won't be able to constant fold this expression even if the operands
|
|
// are constants, return early.
|
|
if (!CanConstantFold(I)) return 0;
|
|
|
|
// Otherwise, we can evaluate this instruction if all of its operands are
|
|
// constant or derived from a PHI node themselves.
|
|
PHINode *PHI = 0;
|
|
for (unsigned Op = 0, e = I->getNumOperands(); Op != e; ++Op)
|
|
if (!(isa<Constant>(I->getOperand(Op)) ||
|
|
isa<GlobalValue>(I->getOperand(Op)))) {
|
|
PHINode *P = getConstantEvolvingPHI(I->getOperand(Op), L);
|
|
if (P == 0) return 0; // Not evolving from PHI
|
|
if (PHI == 0)
|
|
PHI = P;
|
|
else if (PHI != P)
|
|
return 0; // Evolving from multiple different PHIs.
|
|
}
|
|
|
|
// This is a expression evolving from a constant PHI!
|
|
return PHI;
|
|
}
|
|
|
|
/// EvaluateExpression - Given an expression that passes the
|
|
/// getConstantEvolvingPHI predicate, evaluate its value assuming the PHI node
|
|
/// in the loop has the value PHIVal. If we can't fold this expression for some
|
|
/// reason, return null.
|
|
static Constant *EvaluateExpression(Value *V, Constant *PHIVal) {
|
|
if (isa<PHINode>(V)) return PHIVal;
|
|
if (Constant *C = dyn_cast<Constant>(V)) return C;
|
|
Instruction *I = cast<Instruction>(V);
|
|
|
|
std::vector<Constant*> Operands;
|
|
Operands.resize(I->getNumOperands());
|
|
|
|
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
|
|
Operands[i] = EvaluateExpression(I->getOperand(i), PHIVal);
|
|
if (Operands[i] == 0) return 0;
|
|
}
|
|
|
|
if (const CmpInst *CI = dyn_cast<CmpInst>(I))
|
|
return ConstantFoldCompareInstOperands(CI->getPredicate(),
|
|
&Operands[0], Operands.size());
|
|
else
|
|
return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
|
|
&Operands[0], Operands.size());
|
|
}
|
|
|
|
/// getConstantEvolutionLoopExitValue - If we know that the specified Phi is
|
|
/// in the header of its containing loop, we know the loop executes a
|
|
/// constant number of times, and the PHI node is just a recurrence
|
|
/// involving constants, fold it.
|
|
Constant *ScalarEvolutionsImpl::
|
|
getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& BEs, const Loop *L){
|
|
std::map<PHINode*, Constant*>::iterator I =
|
|
ConstantEvolutionLoopExitValue.find(PN);
|
|
if (I != ConstantEvolutionLoopExitValue.end())
|
|
return I->second;
|
|
|
|
if (BEs.ugt(APInt(BEs.getBitWidth(),MaxBruteForceIterations)))
|
|
return ConstantEvolutionLoopExitValue[PN] = 0; // Not going to evaluate it.
|
|
|
|
Constant *&RetVal = ConstantEvolutionLoopExitValue[PN];
|
|
|
|
// Since the loop is canonicalized, the PHI node must have two entries. One
|
|
// entry must be a constant (coming in from outside of the loop), and the
|
|
// second must be derived from the same PHI.
|
|
bool SecondIsBackedge = L->contains(PN->getIncomingBlock(1));
|
|
Constant *StartCST =
|
|
dyn_cast<Constant>(PN->getIncomingValue(!SecondIsBackedge));
|
|
if (StartCST == 0)
|
|
return RetVal = 0; // Must be a constant.
|
|
|
|
Value *BEValue = PN->getIncomingValue(SecondIsBackedge);
|
|
PHINode *PN2 = getConstantEvolvingPHI(BEValue, L);
|
|
if (PN2 != PN)
|
|
return RetVal = 0; // Not derived from same PHI.
|
|
|
|
// Execute the loop symbolically to determine the exit value.
|
|
if (BEs.getActiveBits() >= 32)
|
|
return RetVal = 0; // More than 2^32-1 iterations?? Not doing it!
|
|
|
|
unsigned NumIterations = BEs.getZExtValue(); // must be in range
|
|
unsigned IterationNum = 0;
|
|
for (Constant *PHIVal = StartCST; ; ++IterationNum) {
|
|
if (IterationNum == NumIterations)
|
|
return RetVal = PHIVal; // Got exit value!
|
|
|
|
// Compute the value of the PHI node for the next iteration.
|
|
Constant *NextPHI = EvaluateExpression(BEValue, PHIVal);
|
|
if (NextPHI == PHIVal)
|
|
return RetVal = NextPHI; // Stopped evolving!
|
|
if (NextPHI == 0)
|
|
return 0; // Couldn't evaluate!
|
|
PHIVal = NextPHI;
|
|
}
|
|
}
|
|
|
|
/// ComputeBackedgeTakenCountExhaustively - If the trip is known to execute a
|
|
/// constant number of times (the condition evolves only from constants),
|
|
/// try to evaluate a few iterations of the loop until we get the exit
|
|
/// condition gets a value of ExitWhen (true or false). If we cannot
|
|
/// evaluate the trip count of the loop, return UnknownValue.
|
|
SCEVHandle ScalarEvolutionsImpl::
|
|
ComputeBackedgeTakenCountExhaustively(const Loop *L, Value *Cond, bool ExitWhen) {
|
|
PHINode *PN = getConstantEvolvingPHI(Cond, L);
|
|
if (PN == 0) return UnknownValue;
|
|
|
|
// Since the loop is canonicalized, the PHI node must have two entries. One
|
|
// entry must be a constant (coming in from outside of the loop), and the
|
|
// second must be derived from the same PHI.
|
|
bool SecondIsBackedge = L->contains(PN->getIncomingBlock(1));
|
|
Constant *StartCST =
|
|
dyn_cast<Constant>(PN->getIncomingValue(!SecondIsBackedge));
|
|
if (StartCST == 0) return UnknownValue; // Must be a constant.
|
|
|
|
Value *BEValue = PN->getIncomingValue(SecondIsBackedge);
|
|
PHINode *PN2 = getConstantEvolvingPHI(BEValue, L);
|
|
if (PN2 != PN) return UnknownValue; // Not derived from same PHI.
|
|
|
|
// Okay, we find a PHI node that defines the trip count of this loop. Execute
|
|
// the loop symbolically to determine when the condition gets a value of
|
|
// "ExitWhen".
|
|
unsigned IterationNum = 0;
|
|
unsigned MaxIterations = MaxBruteForceIterations; // Limit analysis.
|
|
for (Constant *PHIVal = StartCST;
|
|
IterationNum != MaxIterations; ++IterationNum) {
|
|
ConstantInt *CondVal =
|
|
dyn_cast_or_null<ConstantInt>(EvaluateExpression(Cond, PHIVal));
|
|
|
|
// Couldn't symbolically evaluate.
|
|
if (!CondVal) return UnknownValue;
|
|
|
|
if (CondVal->getValue() == uint64_t(ExitWhen)) {
|
|
ConstantEvolutionLoopExitValue[PN] = PHIVal;
|
|
++NumBruteForceTripCountsComputed;
|
|
return SE.getConstant(ConstantInt::get(Type::Int32Ty, IterationNum));
|
|
}
|
|
|
|
// Compute the value of the PHI node for the next iteration.
|
|
Constant *NextPHI = EvaluateExpression(BEValue, PHIVal);
|
|
if (NextPHI == 0 || NextPHI == PHIVal)
|
|
return UnknownValue; // Couldn't evaluate or not making progress...
|
|
PHIVal = NextPHI;
|
|
}
|
|
|
|
// Too many iterations were needed to evaluate.
|
|
return UnknownValue;
|
|
}
|
|
|
|
/// getSCEVAtScope - Compute the value of the specified expression within the
|
|
/// indicated loop (which may be null to indicate in no loop). If the
|
|
/// expression cannot be evaluated, return UnknownValue.
|
|
SCEVHandle ScalarEvolutionsImpl::getSCEVAtScope(SCEV *V, const Loop *L) {
|
|
// FIXME: this should be turned into a virtual method on SCEV!
|
|
|
|
if (isa<SCEVConstant>(V)) return V;
|
|
|
|
// If this instruction is evolved from a constant-evolving PHI, compute the
|
|
// exit value from the loop without using SCEVs.
|
|
if (SCEVUnknown *SU = dyn_cast<SCEVUnknown>(V)) {
|
|
if (Instruction *I = dyn_cast<Instruction>(SU->getValue())) {
|
|
const Loop *LI = this->LI[I->getParent()];
|
|
if (LI && LI->getParentLoop() == L) // Looking for loop exit value.
|
|
if (PHINode *PN = dyn_cast<PHINode>(I))
|
|
if (PN->getParent() == LI->getHeader()) {
|
|
// Okay, there is no closed form solution for the PHI node. Check
|
|
// to see if the loop that contains it has a known backedge-taken
|
|
// count. If so, we may be able to force computation of the exit
|
|
// value.
|
|
SCEVHandle BackedgeTakenCount = getBackedgeTakenCount(LI);
|
|
if (SCEVConstant *BTCC =
|
|
dyn_cast<SCEVConstant>(BackedgeTakenCount)) {
|
|
// Okay, we know how many times the containing loop executes. If
|
|
// this is a constant evolving PHI node, get the final value at
|
|
// the specified iteration number.
|
|
Constant *RV = getConstantEvolutionLoopExitValue(PN,
|
|
BTCC->getValue()->getValue(),
|
|
LI);
|
|
if (RV) return SE.getUnknown(RV);
|
|
}
|
|
}
|
|
|
|
// Okay, this is an expression that we cannot symbolically evaluate
|
|
// into a SCEV. Check to see if it's possible to symbolically evaluate
|
|
// the arguments into constants, and if so, try to constant propagate the
|
|
// result. This is particularly useful for computing loop exit values.
|
|
if (CanConstantFold(I)) {
|
|
std::vector<Constant*> Operands;
|
|
Operands.reserve(I->getNumOperands());
|
|
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
|
|
Value *Op = I->getOperand(i);
|
|
if (Constant *C = dyn_cast<Constant>(Op)) {
|
|
Operands.push_back(C);
|
|
} else {
|
|
// If any of the operands is non-constant and if they are
|
|
// non-integer, don't even try to analyze them with scev techniques.
|
|
if (!isa<IntegerType>(Op->getType()))
|
|
return V;
|
|
|
|
SCEVHandle OpV = getSCEVAtScope(getSCEV(Op), L);
|
|
if (SCEVConstant *SC = dyn_cast<SCEVConstant>(OpV))
|
|
Operands.push_back(ConstantExpr::getIntegerCast(SC->getValue(),
|
|
Op->getType(),
|
|
false));
|
|
else if (SCEVUnknown *SU = dyn_cast<SCEVUnknown>(OpV)) {
|
|
if (Constant *C = dyn_cast<Constant>(SU->getValue()))
|
|
Operands.push_back(ConstantExpr::getIntegerCast(C,
|
|
Op->getType(),
|
|
false));
|
|
else
|
|
return V;
|
|
} else {
|
|
return V;
|
|
}
|
|
}
|
|
}
|
|
|
|
Constant *C;
|
|
if (const CmpInst *CI = dyn_cast<CmpInst>(I))
|
|
C = ConstantFoldCompareInstOperands(CI->getPredicate(),
|
|
&Operands[0], Operands.size());
|
|
else
|
|
C = ConstantFoldInstOperands(I->getOpcode(), I->getType(),
|
|
&Operands[0], Operands.size());
|
|
return SE.getUnknown(C);
|
|
}
|
|
}
|
|
|
|
// This is some other type of SCEVUnknown, just return it.
|
|
return V;
|
|
}
|
|
|
|
if (SCEVCommutativeExpr *Comm = dyn_cast<SCEVCommutativeExpr>(V)) {
|
|
// Avoid performing the look-up in the common case where the specified
|
|
// expression has no loop-variant portions.
|
|
for (unsigned i = 0, e = Comm->getNumOperands(); i != e; ++i) {
|
|
SCEVHandle OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
|
|
if (OpAtScope != Comm->getOperand(i)) {
|
|
if (OpAtScope == UnknownValue) return UnknownValue;
|
|
// Okay, at least one of these operands is loop variant but might be
|
|
// foldable. Build a new instance of the folded commutative expression.
|
|
std::vector<SCEVHandle> NewOps(Comm->op_begin(), Comm->op_begin()+i);
|
|
NewOps.push_back(OpAtScope);
|
|
|
|
for (++i; i != e; ++i) {
|
|
OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
|
|
if (OpAtScope == UnknownValue) return UnknownValue;
|
|
NewOps.push_back(OpAtScope);
|
|
}
|
|
if (isa<SCEVAddExpr>(Comm))
|
|
return SE.getAddExpr(NewOps);
|
|
if (isa<SCEVMulExpr>(Comm))
|
|
return SE.getMulExpr(NewOps);
|
|
if (isa<SCEVSMaxExpr>(Comm))
|
|
return SE.getSMaxExpr(NewOps);
|
|
if (isa<SCEVUMaxExpr>(Comm))
|
|
return SE.getUMaxExpr(NewOps);
|
|
assert(0 && "Unknown commutative SCEV type!");
|
|
}
|
|
}
|
|
// If we got here, all operands are loop invariant.
|
|
return Comm;
|
|
}
|
|
|
|
if (SCEVUDivExpr *Div = dyn_cast<SCEVUDivExpr>(V)) {
|
|
SCEVHandle LHS = getSCEVAtScope(Div->getLHS(), L);
|
|
if (LHS == UnknownValue) return LHS;
|
|
SCEVHandle RHS = getSCEVAtScope(Div->getRHS(), L);
|
|
if (RHS == UnknownValue) return RHS;
|
|
if (LHS == Div->getLHS() && RHS == Div->getRHS())
|
|
return Div; // must be loop invariant
|
|
return SE.getUDivExpr(LHS, RHS);
|
|
}
|
|
|
|
// If this is a loop recurrence for a loop that does not contain L, then we
|
|
// are dealing with the final value computed by the loop.
|
|
if (SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V)) {
|
|
if (!L || !AddRec->getLoop()->contains(L->getHeader())) {
|
|
// To evaluate this recurrence, we need to know how many times the AddRec
|
|
// loop iterates. Compute this now.
|
|
SCEVHandle BackedgeTakenCount = getBackedgeTakenCount(AddRec->getLoop());
|
|
if (BackedgeTakenCount == UnknownValue) return UnknownValue;
|
|
|
|
// Then, evaluate the AddRec.
|
|
return AddRec->evaluateAtIteration(BackedgeTakenCount, SE);
|
|
}
|
|
return UnknownValue;
|
|
}
|
|
|
|
//assert(0 && "Unknown SCEV type!");
|
|
return UnknownValue;
|
|
}
|
|
|
|
/// SolveLinEquationWithOverflow - Finds the minimum unsigned root of the
|
|
/// following equation:
|
|
///
|
|
/// A * X = B (mod N)
|
|
///
|
|
/// where N = 2^BW and BW is the common bit width of A and B. The signedness of
|
|
/// A and B isn't important.
|
|
///
|
|
/// If the equation does not have a solution, SCEVCouldNotCompute is returned.
|
|
static SCEVHandle SolveLinEquationWithOverflow(const APInt &A, const APInt &B,
|
|
ScalarEvolution &SE) {
|
|
uint32_t BW = A.getBitWidth();
|
|
assert(BW == B.getBitWidth() && "Bit widths must be the same.");
|
|
assert(A != 0 && "A must be non-zero.");
|
|
|
|
// 1. D = gcd(A, N)
|
|
//
|
|
// The gcd of A and N may have only one prime factor: 2. The number of
|
|
// trailing zeros in A is its multiplicity
|
|
uint32_t Mult2 = A.countTrailingZeros();
|
|
// D = 2^Mult2
|
|
|
|
// 2. Check if B is divisible by D.
|
|
//
|
|
// B is divisible by D if and only if the multiplicity of prime factor 2 for B
|
|
// is not less than multiplicity of this prime factor for D.
|
|
if (B.countTrailingZeros() < Mult2)
|
|
return new SCEVCouldNotCompute();
|
|
|
|
// 3. Compute I: the multiplicative inverse of (A / D) in arithmetic
|
|
// modulo (N / D).
|
|
//
|
|
// (N / D) may need BW+1 bits in its representation. Hence, we'll use this
|
|
// bit width during computations.
|
|
APInt AD = A.lshr(Mult2).zext(BW + 1); // AD = A / D
|
|
APInt Mod(BW + 1, 0);
|
|
Mod.set(BW - Mult2); // Mod = N / D
|
|
APInt I = AD.multiplicativeInverse(Mod);
|
|
|
|
// 4. Compute the minimum unsigned root of the equation:
|
|
// I * (B / D) mod (N / D)
|
|
APInt Result = (I * B.lshr(Mult2).zext(BW + 1)).urem(Mod);
|
|
|
|
// The result is guaranteed to be less than 2^BW so we may truncate it to BW
|
|
// bits.
|
|
return SE.getConstant(Result.trunc(BW));
|
|
}
|
|
|
|
/// SolveQuadraticEquation - Find the roots of the quadratic equation for the
|
|
/// given quadratic chrec {L,+,M,+,N}. This returns either the two roots (which
|
|
/// might be the same) or two SCEVCouldNotCompute objects.
|
|
///
|
|
static std::pair<SCEVHandle,SCEVHandle>
|
|
SolveQuadraticEquation(const SCEVAddRecExpr *AddRec, ScalarEvolution &SE) {
|
|
assert(AddRec->getNumOperands() == 3 && "This is not a quadratic chrec!");
|
|
SCEVConstant *LC = dyn_cast<SCEVConstant>(AddRec->getOperand(0));
|
|
SCEVConstant *MC = dyn_cast<SCEVConstant>(AddRec->getOperand(1));
|
|
SCEVConstant *NC = dyn_cast<SCEVConstant>(AddRec->getOperand(2));
|
|
|
|
// We currently can only solve this if the coefficients are constants.
|
|
if (!LC || !MC || !NC) {
|
|
SCEV *CNC = new SCEVCouldNotCompute();
|
|
return std::make_pair(CNC, CNC);
|
|
}
|
|
|
|
uint32_t BitWidth = LC->getValue()->getValue().getBitWidth();
|
|
const APInt &L = LC->getValue()->getValue();
|
|
const APInt &M = MC->getValue()->getValue();
|
|
const APInt &N = NC->getValue()->getValue();
|
|
APInt Two(BitWidth, 2);
|
|
APInt Four(BitWidth, 4);
|
|
|
|
{
|
|
using namespace APIntOps;
|
|
const APInt& C = L;
|
|
// Convert from chrec coefficients to polynomial coefficients AX^2+BX+C
|
|
// The B coefficient is M-N/2
|
|
APInt B(M);
|
|
B -= sdiv(N,Two);
|
|
|
|
// The A coefficient is N/2
|
|
APInt A(N.sdiv(Two));
|
|
|
|
// Compute the B^2-4ac term.
|
|
APInt SqrtTerm(B);
|
|
SqrtTerm *= B;
|
|
SqrtTerm -= Four * (A * C);
|
|
|
|
// Compute sqrt(B^2-4ac). This is guaranteed to be the nearest
|
|
// integer value or else APInt::sqrt() will assert.
|
|
APInt SqrtVal(SqrtTerm.sqrt());
|
|
|
|
// Compute the two solutions for the quadratic formula.
|
|
// The divisions must be performed as signed divisions.
|
|
APInt NegB(-B);
|
|
APInt TwoA( A << 1 );
|
|
if (TwoA.isMinValue()) {
|
|
SCEV *CNC = new SCEVCouldNotCompute();
|
|
return std::make_pair(CNC, CNC);
|
|
}
|
|
|
|
ConstantInt *Solution1 = ConstantInt::get((NegB + SqrtVal).sdiv(TwoA));
|
|
ConstantInt *Solution2 = ConstantInt::get((NegB - SqrtVal).sdiv(TwoA));
|
|
|
|
return std::make_pair(SE.getConstant(Solution1),
|
|
SE.getConstant(Solution2));
|
|
} // end APIntOps namespace
|
|
}
|
|
|
|
/// HowFarToZero - Return the number of times a backedge comparing the specified
|
|
/// value to zero will execute. If not computable, return UnknownValue
|
|
SCEVHandle ScalarEvolutionsImpl::HowFarToZero(SCEV *V, const Loop *L) {
|
|
// If the value is a constant
|
|
if (SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
|
|
// If the value is already zero, the branch will execute zero times.
|
|
if (C->getValue()->isZero()) return C;
|
|
return UnknownValue; // Otherwise it will loop infinitely.
|
|
}
|
|
|
|
SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V);
|
|
if (!AddRec || AddRec->getLoop() != L)
|
|
return UnknownValue;
|
|
|
|
if (AddRec->isAffine()) {
|
|
// If this is an affine expression, the execution count of this branch is
|
|
// the minimum unsigned root of the following equation:
|
|
//
|
|
// Start + Step*N = 0 (mod 2^BW)
|
|
//
|
|
// equivalent to:
|
|
//
|
|
// Step*N = -Start (mod 2^BW)
|
|
//
|
|
// where BW is the common bit width of Start and Step.
|
|
|
|
// Get the initial value for the loop.
|
|
SCEVHandle Start = getSCEVAtScope(AddRec->getStart(), L->getParentLoop());
|
|
if (isa<SCEVCouldNotCompute>(Start)) return UnknownValue;
|
|
|
|
SCEVHandle Step = getSCEVAtScope(AddRec->getOperand(1), L->getParentLoop());
|
|
|
|
if (SCEVConstant *StepC = dyn_cast<SCEVConstant>(Step)) {
|
|
// For now we handle only constant steps.
|
|
|
|
// First, handle unitary steps.
|
|
if (StepC->getValue()->equalsInt(1)) // 1*N = -Start (mod 2^BW), so:
|
|
return SE.getNegativeSCEV(Start); // N = -Start (as unsigned)
|
|
if (StepC->getValue()->isAllOnesValue()) // -1*N = -Start (mod 2^BW), so:
|
|
return Start; // N = Start (as unsigned)
|
|
|
|
// Then, try to solve the above equation provided that Start is constant.
|
|
if (SCEVConstant *StartC = dyn_cast<SCEVConstant>(Start))
|
|
return SolveLinEquationWithOverflow(StepC->getValue()->getValue(),
|
|
-StartC->getValue()->getValue(),SE);
|
|
}
|
|
} else if (AddRec->isQuadratic() && AddRec->getType()->isInteger()) {
|
|
// If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of
|
|
// the quadratic equation to solve it.
|
|
std::pair<SCEVHandle,SCEVHandle> Roots = SolveQuadraticEquation(AddRec, SE);
|
|
SCEVConstant *R1 = dyn_cast<SCEVConstant>(Roots.first);
|
|
SCEVConstant *R2 = dyn_cast<SCEVConstant>(Roots.second);
|
|
if (R1) {
|
|
#if 0
|
|
cerr << "HFTZ: " << *V << " - sol#1: " << *R1
|
|
<< " sol#2: " << *R2 << "\n";
|
|
#endif
|
|
// Pick the smallest positive root value.
|
|
if (ConstantInt *CB =
|
|
dyn_cast<ConstantInt>(ConstantExpr::getICmp(ICmpInst::ICMP_ULT,
|
|
R1->getValue(), R2->getValue()))) {
|
|
if (CB->getZExtValue() == false)
|
|
std::swap(R1, R2); // R1 is the minimum root now.
|
|
|
|
// We can only use this value if the chrec ends up with an exact zero
|
|
// value at this index. When solving for "X*X != 5", for example, we
|
|
// should not accept a root of 2.
|
|
SCEVHandle Val = AddRec->evaluateAtIteration(R1, SE);
|
|
if (Val->isZero())
|
|
return R1; // We found a quadratic root!
|
|
}
|
|
}
|
|
}
|
|
|
|
return UnknownValue;
|
|
}
|
|
|
|
/// HowFarToNonZero - Return the number of times a backedge checking the
|
|
/// specified value for nonzero will execute. If not computable, return
|
|
/// UnknownValue
|
|
SCEVHandle ScalarEvolutionsImpl::HowFarToNonZero(SCEV *V, const Loop *L) {
|
|
// Loops that look like: while (X == 0) are very strange indeed. We don't
|
|
// handle them yet except for the trivial case. This could be expanded in the
|
|
// future as needed.
|
|
|
|
// If the value is a constant, check to see if it is known to be non-zero
|
|
// already. If so, the backedge will execute zero times.
|
|
if (SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
|
|
if (!C->getValue()->isNullValue())
|
|
return SE.getIntegerSCEV(0, C->getType());
|
|
return UnknownValue; // Otherwise it will loop infinitely.
|
|
}
|
|
|
|
// We could implement others, but I really doubt anyone writes loops like
|
|
// this, and if they did, they would already be constant folded.
|
|
return UnknownValue;
|
|
}
|
|
|
|
/// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB
|
|
/// (which may not be an immediate predecessor) which has exactly one
|
|
/// successor from which BB is reachable, or null if no such block is
|
|
/// found.
|
|
///
|
|
BasicBlock *
|
|
ScalarEvolutionsImpl::getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB) {
|
|
// If the block has a unique predecessor, the predecessor must have
|
|
// no other successors from which BB is reachable.
|
|
if (BasicBlock *Pred = BB->getSinglePredecessor())
|
|
return Pred;
|
|
|
|
// A loop's header is defined to be a block that dominates the loop.
|
|
// If the loop has a preheader, it must be a block that has exactly
|
|
// one successor that can reach BB. This is slightly more strict
|
|
// than necessary, but works if critical edges are split.
|
|
if (Loop *L = LI.getLoopFor(BB))
|
|
return L->getLoopPreheader();
|
|
|
|
return 0;
|
|
}
|
|
|
|
/// isLoopGuardedByCond - Test whether entry to the loop is protected by
|
|
/// a conditional between LHS and RHS.
|
|
bool ScalarEvolutionsImpl::isLoopGuardedByCond(const Loop *L,
|
|
ICmpInst::Predicate Pred,
|
|
SCEV *LHS, SCEV *RHS) {
|
|
BasicBlock *Preheader = L->getLoopPreheader();
|
|
BasicBlock *PreheaderDest = L->getHeader();
|
|
|
|
// Starting at the preheader, climb up the predecessor chain, as long as
|
|
// there are predecessors that can be found that have unique successors
|
|
// leading to the original header.
|
|
for (; Preheader;
|
|
PreheaderDest = Preheader,
|
|
Preheader = getPredecessorWithUniqueSuccessorForBB(Preheader)) {
|
|
|
|
BranchInst *LoopEntryPredicate =
|
|
dyn_cast<BranchInst>(Preheader->getTerminator());
|
|
if (!LoopEntryPredicate ||
|
|
LoopEntryPredicate->isUnconditional())
|
|
continue;
|
|
|
|
ICmpInst *ICI = dyn_cast<ICmpInst>(LoopEntryPredicate->getCondition());
|
|
if (!ICI) continue;
|
|
|
|
// Now that we found a conditional branch that dominates the loop, check to
|
|
// see if it is the comparison we are looking for.
|
|
Value *PreCondLHS = ICI->getOperand(0);
|
|
Value *PreCondRHS = ICI->getOperand(1);
|
|
ICmpInst::Predicate Cond;
|
|
if (LoopEntryPredicate->getSuccessor(0) == PreheaderDest)
|
|
Cond = ICI->getPredicate();
|
|
else
|
|
Cond = ICI->getInversePredicate();
|
|
|
|
if (Cond == Pred)
|
|
; // An exact match.
|
|
else if (!ICmpInst::isTrueWhenEqual(Cond) && Pred == ICmpInst::ICMP_NE)
|
|
; // The actual condition is beyond sufficient.
|
|
else
|
|
// Check a few special cases.
|
|
switch (Cond) {
|
|
case ICmpInst::ICMP_UGT:
|
|
if (Pred == ICmpInst::ICMP_ULT) {
|
|
std::swap(PreCondLHS, PreCondRHS);
|
|
Cond = ICmpInst::ICMP_ULT;
|
|
break;
|
|
}
|
|
continue;
|
|
case ICmpInst::ICMP_SGT:
|
|
if (Pred == ICmpInst::ICMP_SLT) {
|
|
std::swap(PreCondLHS, PreCondRHS);
|
|
Cond = ICmpInst::ICMP_SLT;
|
|
break;
|
|
}
|
|
continue;
|
|
case ICmpInst::ICMP_NE:
|
|
// Expressions like (x >u 0) are often canonicalized to (x != 0),
|
|
// so check for this case by checking if the NE is comparing against
|
|
// a minimum or maximum constant.
|
|
if (!ICmpInst::isTrueWhenEqual(Pred))
|
|
if (ConstantInt *CI = dyn_cast<ConstantInt>(PreCondRHS)) {
|
|
const APInt &A = CI->getValue();
|
|
switch (Pred) {
|
|
case ICmpInst::ICMP_SLT:
|
|
if (A.isMaxSignedValue()) break;
|
|
continue;
|
|
case ICmpInst::ICMP_SGT:
|
|
if (A.isMinSignedValue()) break;
|
|
continue;
|
|
case ICmpInst::ICMP_ULT:
|
|
if (A.isMaxValue()) break;
|
|
continue;
|
|
case ICmpInst::ICMP_UGT:
|
|
if (A.isMinValue()) break;
|
|
continue;
|
|
default:
|
|
continue;
|
|
}
|
|
Cond = ICmpInst::ICMP_NE;
|
|
// NE is symmetric but the original comparison may not be. Swap
|
|
// the operands if necessary so that they match below.
|
|
if (isa<SCEVConstant>(LHS))
|
|
std::swap(PreCondLHS, PreCondRHS);
|
|
break;
|
|
}
|
|
continue;
|
|
default:
|
|
// We weren't able to reconcile the condition.
|
|
continue;
|
|
}
|
|
|
|
if (!PreCondLHS->getType()->isInteger()) continue;
|
|
|
|
SCEVHandle PreCondLHSSCEV = getSCEV(PreCondLHS);
|
|
SCEVHandle PreCondRHSSCEV = getSCEV(PreCondRHS);
|
|
if ((LHS == PreCondLHSSCEV && RHS == PreCondRHSSCEV) ||
|
|
(LHS == SE.getNotSCEV(PreCondRHSSCEV) &&
|
|
RHS == SE.getNotSCEV(PreCondLHSSCEV)))
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
/// HowManyLessThans - Return the number of times a backedge containing the
|
|
/// specified less-than comparison will execute. If not computable, return
|
|
/// UnknownValue.
|
|
SCEVHandle ScalarEvolutionsImpl::
|
|
HowManyLessThans(SCEV *LHS, SCEV *RHS, const Loop *L, bool isSigned) {
|
|
// Only handle: "ADDREC < LoopInvariant".
|
|
if (!RHS->isLoopInvariant(L)) return UnknownValue;
|
|
|
|
SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS);
|
|
if (!AddRec || AddRec->getLoop() != L)
|
|
return UnknownValue;
|
|
|
|
if (AddRec->isAffine()) {
|
|
// FORNOW: We only support unit strides.
|
|
SCEVHandle One = SE.getIntegerSCEV(1, RHS->getType());
|
|
if (AddRec->getOperand(1) != One)
|
|
return UnknownValue;
|
|
|
|
// We know the LHS is of the form {n,+,1} and the RHS is some loop-invariant
|
|
// m. So, we count the number of iterations in which {n,+,1} < m is true.
|
|
// Note that we cannot simply return max(m-n,0) because it's not safe to
|
|
// treat m-n as signed nor unsigned due to overflow possibility.
|
|
|
|
// First, we get the value of the LHS in the first iteration: n
|
|
SCEVHandle Start = AddRec->getOperand(0);
|
|
|
|
if (isLoopGuardedByCond(L,
|
|
isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
|
|
SE.getMinusSCEV(AddRec->getOperand(0), One), RHS)) {
|
|
// Since we know that the condition is true in order to enter the loop,
|
|
// we know that it will run exactly m-n times.
|
|
return SE.getMinusSCEV(RHS, Start);
|
|
} else {
|
|
// Then, we get the value of the LHS in the first iteration in which the
|
|
// above condition doesn't hold. This equals to max(m,n).
|
|
SCEVHandle End = isSigned ? SE.getSMaxExpr(RHS, Start)
|
|
: SE.getUMaxExpr(RHS, Start);
|
|
|
|
// Finally, we subtract these two values to get the number of times the
|
|
// backedge is executed: max(m,n)-n.
|
|
return SE.getMinusSCEV(End, Start);
|
|
}
|
|
}
|
|
|
|
return UnknownValue;
|
|
}
|
|
|
|
/// getNumIterationsInRange - Return the number of iterations of this loop that
|
|
/// produce values in the specified constant range. Another way of looking at
|
|
/// this is that it returns the first iteration number where the value is not in
|
|
/// the condition, thus computing the exit count. If the iteration count can't
|
|
/// be computed, an instance of SCEVCouldNotCompute is returned.
|
|
SCEVHandle SCEVAddRecExpr::getNumIterationsInRange(ConstantRange Range,
|
|
ScalarEvolution &SE) const {
|
|
if (Range.isFullSet()) // Infinite loop.
|
|
return new SCEVCouldNotCompute();
|
|
|
|
// If the start is a non-zero constant, shift the range to simplify things.
|
|
if (SCEVConstant *SC = dyn_cast<SCEVConstant>(getStart()))
|
|
if (!SC->getValue()->isZero()) {
|
|
std::vector<SCEVHandle> Operands(op_begin(), op_end());
|
|
Operands[0] = SE.getIntegerSCEV(0, SC->getType());
|
|
SCEVHandle Shifted = SE.getAddRecExpr(Operands, getLoop());
|
|
if (SCEVAddRecExpr *ShiftedAddRec = dyn_cast<SCEVAddRecExpr>(Shifted))
|
|
return ShiftedAddRec->getNumIterationsInRange(
|
|
Range.subtract(SC->getValue()->getValue()), SE);
|
|
// This is strange and shouldn't happen.
|
|
return new SCEVCouldNotCompute();
|
|
}
|
|
|
|
// The only time we can solve this is when we have all constant indices.
|
|
// Otherwise, we cannot determine the overflow conditions.
|
|
for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
|
|
if (!isa<SCEVConstant>(getOperand(i)))
|
|
return new SCEVCouldNotCompute();
|
|
|
|
|
|
// Okay at this point we know that all elements of the chrec are constants and
|
|
// that the start element is zero.
|
|
|
|
// First check to see if the range contains zero. If not, the first
|
|
// iteration exits.
|
|
if (!Range.contains(APInt(getBitWidth(),0)))
|
|
return SE.getConstant(ConstantInt::get(getType(),0));
|
|
|
|
if (isAffine()) {
|
|
// If this is an affine expression then we have this situation:
|
|
// Solve {0,+,A} in Range === Ax in Range
|
|
|
|
// We know that zero is in the range. If A is positive then we know that
|
|
// the upper value of the range must be the first possible exit value.
|
|
// If A is negative then the lower of the range is the last possible loop
|
|
// value. Also note that we already checked for a full range.
|
|
APInt One(getBitWidth(),1);
|
|
APInt A = cast<SCEVConstant>(getOperand(1))->getValue()->getValue();
|
|
APInt End = A.sge(One) ? (Range.getUpper() - One) : Range.getLower();
|
|
|
|
// The exit value should be (End+A)/A.
|
|
APInt ExitVal = (End + A).udiv(A);
|
|
ConstantInt *ExitValue = ConstantInt::get(ExitVal);
|
|
|
|
// Evaluate at the exit value. If we really did fall out of the valid
|
|
// range, then we computed our trip count, otherwise wrap around or other
|
|
// things must have happened.
|
|
ConstantInt *Val = EvaluateConstantChrecAtConstant(this, ExitValue, SE);
|
|
if (Range.contains(Val->getValue()))
|
|
return new SCEVCouldNotCompute(); // Something strange happened
|
|
|
|
// Ensure that the previous value is in the range. This is a sanity check.
|
|
assert(Range.contains(
|
|
EvaluateConstantChrecAtConstant(this,
|
|
ConstantInt::get(ExitVal - One), SE)->getValue()) &&
|
|
"Linear scev computation is off in a bad way!");
|
|
return SE.getConstant(ExitValue);
|
|
} else if (isQuadratic()) {
|
|
// If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of the
|
|
// quadratic equation to solve it. To do this, we must frame our problem in
|
|
// terms of figuring out when zero is crossed, instead of when
|
|
// Range.getUpper() is crossed.
|
|
std::vector<SCEVHandle> NewOps(op_begin(), op_end());
|
|
NewOps[0] = SE.getNegativeSCEV(SE.getConstant(Range.getUpper()));
|
|
SCEVHandle NewAddRec = SE.getAddRecExpr(NewOps, getLoop());
|
|
|
|
// Next, solve the constructed addrec
|
|
std::pair<SCEVHandle,SCEVHandle> Roots =
|
|
SolveQuadraticEquation(cast<SCEVAddRecExpr>(NewAddRec), SE);
|
|
SCEVConstant *R1 = dyn_cast<SCEVConstant>(Roots.first);
|
|
SCEVConstant *R2 = dyn_cast<SCEVConstant>(Roots.second);
|
|
if (R1) {
|
|
// Pick the smallest positive root value.
|
|
if (ConstantInt *CB =
|
|
dyn_cast<ConstantInt>(ConstantExpr::getICmp(ICmpInst::ICMP_ULT,
|
|
R1->getValue(), R2->getValue()))) {
|
|
if (CB->getZExtValue() == false)
|
|
std::swap(R1, R2); // R1 is the minimum root now.
|
|
|
|
// Make sure the root is not off by one. The returned iteration should
|
|
// not be in the range, but the previous one should be. When solving
|
|
// for "X*X < 5", for example, we should not return a root of 2.
|
|
ConstantInt *R1Val = EvaluateConstantChrecAtConstant(this,
|
|
R1->getValue(),
|
|
SE);
|
|
if (Range.contains(R1Val->getValue())) {
|
|
// The next iteration must be out of the range...
|
|
ConstantInt *NextVal = ConstantInt::get(R1->getValue()->getValue()+1);
|
|
|
|
R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
|
|
if (!Range.contains(R1Val->getValue()))
|
|
return SE.getConstant(NextVal);
|
|
return new SCEVCouldNotCompute(); // Something strange happened
|
|
}
|
|
|
|
// If R1 was not in the range, then it is a good return value. Make
|
|
// sure that R1-1 WAS in the range though, just in case.
|
|
ConstantInt *NextVal = ConstantInt::get(R1->getValue()->getValue()-1);
|
|
R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
|
|
if (Range.contains(R1Val->getValue()))
|
|
return R1;
|
|
return new SCEVCouldNotCompute(); // Something strange happened
|
|
}
|
|
}
|
|
}
|
|
|
|
return new SCEVCouldNotCompute();
|
|
}
|
|
|
|
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// ScalarEvolution Class Implementation
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
bool ScalarEvolution::runOnFunction(Function &F) {
|
|
Impl = new ScalarEvolutionsImpl(*this, F, getAnalysis<LoopInfo>());
|
|
return false;
|
|
}
|
|
|
|
void ScalarEvolution::releaseMemory() {
|
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delete (ScalarEvolutionsImpl*)Impl;
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Impl = 0;
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}
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void ScalarEvolution::getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesAll();
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AU.addRequiredTransitive<LoopInfo>();
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}
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SCEVHandle ScalarEvolution::getSCEV(Value *V) const {
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return ((ScalarEvolutionsImpl*)Impl)->getSCEV(V);
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}
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/// hasSCEV - Return true if the SCEV for this value has already been
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/// computed.
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bool ScalarEvolution::hasSCEV(Value *V) const {
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return ((ScalarEvolutionsImpl*)Impl)->hasSCEV(V);
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}
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/// setSCEV - Insert the specified SCEV into the map of current SCEVs for
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/// the specified value.
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void ScalarEvolution::setSCEV(Value *V, const SCEVHandle &H) {
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((ScalarEvolutionsImpl*)Impl)->setSCEV(V, H);
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}
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bool ScalarEvolution::isLoopGuardedByCond(const Loop *L,
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ICmpInst::Predicate Pred,
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SCEV *LHS, SCEV *RHS) {
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return ((ScalarEvolutionsImpl*)Impl)->isLoopGuardedByCond(L, Pred,
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LHS, RHS);
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}
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SCEVHandle ScalarEvolution::getBackedgeTakenCount(const Loop *L) const {
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return ((ScalarEvolutionsImpl*)Impl)->getBackedgeTakenCount(L);
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}
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bool ScalarEvolution::hasLoopInvariantBackedgeTakenCount(const Loop *L) const {
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return !isa<SCEVCouldNotCompute>(getBackedgeTakenCount(L));
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}
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void ScalarEvolution::forgetLoopBackedgeTakenCount(const Loop *L) {
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return ((ScalarEvolutionsImpl*)Impl)->forgetLoopBackedgeTakenCount(L);
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}
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SCEVHandle ScalarEvolution::getSCEVAtScope(Value *V, const Loop *L) const {
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return ((ScalarEvolutionsImpl*)Impl)->getSCEVAtScope(getSCEV(V), L);
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}
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void ScalarEvolution::deleteValueFromRecords(Value *V) const {
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return ((ScalarEvolutionsImpl*)Impl)->deleteValueFromRecords(V);
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}
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static void PrintLoopInfo(std::ostream &OS, const ScalarEvolution *SE,
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const Loop *L) {
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// Print all inner loops first
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for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
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PrintLoopInfo(OS, SE, *I);
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OS << "Loop " << L->getHeader()->getName() << ": ";
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SmallVector<BasicBlock*, 8> ExitBlocks;
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L->getExitBlocks(ExitBlocks);
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if (ExitBlocks.size() != 1)
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OS << "<multiple exits> ";
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if (SE->hasLoopInvariantBackedgeTakenCount(L)) {
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OS << "backedge-taken count is " << *SE->getBackedgeTakenCount(L);
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} else {
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OS << "Unpredictable backedge-taken count. ";
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}
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OS << "\n";
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}
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void ScalarEvolution::print(std::ostream &OS, const Module* ) const {
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Function &F = ((ScalarEvolutionsImpl*)Impl)->F;
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LoopInfo &LI = ((ScalarEvolutionsImpl*)Impl)->LI;
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OS << "Classifying expressions for: " << F.getName() << "\n";
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for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
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if (I->getType()->isInteger()) {
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OS << *I;
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OS << " --> ";
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SCEVHandle SV = getSCEV(&*I);
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SV->print(OS);
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OS << "\t\t";
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if (const Loop *L = LI.getLoopFor((*I).getParent())) {
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OS << "Exits: ";
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SCEVHandle ExitValue = getSCEVAtScope(&*I, L->getParentLoop());
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if (isa<SCEVCouldNotCompute>(ExitValue)) {
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OS << "<<Unknown>>";
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} else {
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OS << *ExitValue;
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}
|
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}
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OS << "\n";
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}
|
|
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OS << "Determining loop execution counts for: " << F.getName() << "\n";
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|
for (LoopInfo::iterator I = LI.begin(), E = LI.end(); I != E; ++I)
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PrintLoopInfo(OS, this, *I);
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}
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