mirror of
https://github.com/c64scene-ar/llvm-6502.git
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135375 91177308-0d34-0410-b5e6-96231b3b80d8
1129 lines
38 KiB
C++
1129 lines
38 KiB
C++
//===- LazyValueInfo.cpp - Value constraint analysis ----------------------===//
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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 defines the interface for lazy computation of value constraint
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// information.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "lazy-value-info"
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#include "llvm/Analysis/LazyValueInfo.h"
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#include "llvm/Analysis/ValueTracking.h"
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#include "llvm/Constants.h"
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#include "llvm/Instructions.h"
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#include "llvm/IntrinsicInst.h"
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#include "llvm/Analysis/ConstantFolding.h"
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#include "llvm/Target/TargetData.h"
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#include "llvm/Support/CFG.h"
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#include "llvm/Support/ConstantRange.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Support/ValueHandle.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/DenseSet.h"
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#include "llvm/ADT/STLExtras.h"
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#include <map>
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#include <stack>
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using namespace llvm;
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char LazyValueInfo::ID = 0;
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INITIALIZE_PASS(LazyValueInfo, "lazy-value-info",
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"Lazy Value Information Analysis", false, true)
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namespace llvm {
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FunctionPass *createLazyValueInfoPass() { return new LazyValueInfo(); }
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}
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//===----------------------------------------------------------------------===//
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// LVILatticeVal
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//===----------------------------------------------------------------------===//
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/// LVILatticeVal - This is the information tracked by LazyValueInfo for each
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/// value.
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///
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/// FIXME: This is basically just for bringup, this can be made a lot more rich
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/// in the future.
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///
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namespace {
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class LVILatticeVal {
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enum LatticeValueTy {
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/// undefined - This Value has no known value yet.
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undefined,
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/// constant - This Value has a specific constant value.
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constant,
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/// notconstant - This Value is known to not have the specified value.
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notconstant,
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/// constantrange - The Value falls within this range.
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constantrange,
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/// overdefined - This value is not known to be constant, and we know that
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/// it has a value.
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overdefined
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};
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/// Val: This stores the current lattice value along with the Constant* for
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/// the constant if this is a 'constant' or 'notconstant' value.
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LatticeValueTy Tag;
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Constant *Val;
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ConstantRange Range;
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public:
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LVILatticeVal() : Tag(undefined), Val(0), Range(1, true) {}
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static LVILatticeVal get(Constant *C) {
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LVILatticeVal Res;
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if (!isa<UndefValue>(C))
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Res.markConstant(C);
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return Res;
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}
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static LVILatticeVal getNot(Constant *C) {
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LVILatticeVal Res;
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if (!isa<UndefValue>(C))
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Res.markNotConstant(C);
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return Res;
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}
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static LVILatticeVal getRange(ConstantRange CR) {
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LVILatticeVal Res;
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Res.markConstantRange(CR);
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return Res;
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}
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bool isUndefined() const { return Tag == undefined; }
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bool isConstant() const { return Tag == constant; }
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bool isNotConstant() const { return Tag == notconstant; }
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bool isConstantRange() const { return Tag == constantrange; }
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bool isOverdefined() const { return Tag == overdefined; }
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Constant *getConstant() const {
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assert(isConstant() && "Cannot get the constant of a non-constant!");
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return Val;
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}
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Constant *getNotConstant() const {
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assert(isNotConstant() && "Cannot get the constant of a non-notconstant!");
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return Val;
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}
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ConstantRange getConstantRange() const {
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assert(isConstantRange() &&
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"Cannot get the constant-range of a non-constant-range!");
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return Range;
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}
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/// markOverdefined - Return true if this is a change in status.
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bool markOverdefined() {
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if (isOverdefined())
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return false;
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Tag = overdefined;
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return true;
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}
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/// markConstant - Return true if this is a change in status.
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bool markConstant(Constant *V) {
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assert(V && "Marking constant with NULL");
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if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
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return markConstantRange(ConstantRange(CI->getValue()));
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if (isa<UndefValue>(V))
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return false;
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assert((!isConstant() || getConstant() == V) &&
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"Marking constant with different value");
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assert(isUndefined());
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Tag = constant;
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Val = V;
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return true;
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}
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/// markNotConstant - Return true if this is a change in status.
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bool markNotConstant(Constant *V) {
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assert(V && "Marking constant with NULL");
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if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
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return markConstantRange(ConstantRange(CI->getValue()+1, CI->getValue()));
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if (isa<UndefValue>(V))
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return false;
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assert((!isConstant() || getConstant() != V) &&
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"Marking constant !constant with same value");
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assert((!isNotConstant() || getNotConstant() == V) &&
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"Marking !constant with different value");
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assert(isUndefined() || isConstant());
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Tag = notconstant;
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Val = V;
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return true;
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}
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/// markConstantRange - Return true if this is a change in status.
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bool markConstantRange(const ConstantRange NewR) {
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if (isConstantRange()) {
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if (NewR.isEmptySet())
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return markOverdefined();
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bool changed = Range == NewR;
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Range = NewR;
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return changed;
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}
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assert(isUndefined());
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if (NewR.isEmptySet())
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return markOverdefined();
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Tag = constantrange;
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Range = NewR;
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return true;
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}
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/// mergeIn - Merge the specified lattice value into this one, updating this
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/// one and returning true if anything changed.
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bool mergeIn(const LVILatticeVal &RHS) {
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if (RHS.isUndefined() || isOverdefined()) return false;
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if (RHS.isOverdefined()) return markOverdefined();
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if (isUndefined()) {
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Tag = RHS.Tag;
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Val = RHS.Val;
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Range = RHS.Range;
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return true;
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}
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if (isConstant()) {
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if (RHS.isConstant()) {
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if (Val == RHS.Val)
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return false;
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return markOverdefined();
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}
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if (RHS.isNotConstant()) {
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if (Val == RHS.Val)
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return markOverdefined();
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// Unless we can prove that the two Constants are different, we must
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// move to overdefined.
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// FIXME: use TargetData for smarter constant folding.
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if (ConstantInt *Res = dyn_cast<ConstantInt>(
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ConstantFoldCompareInstOperands(CmpInst::ICMP_NE,
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getConstant(),
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RHS.getNotConstant())))
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if (Res->isOne())
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return markNotConstant(RHS.getNotConstant());
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return markOverdefined();
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}
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// RHS is a ConstantRange, LHS is a non-integer Constant.
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// FIXME: consider the case where RHS is a range [1, 0) and LHS is
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// a function. The correct result is to pick up RHS.
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return markOverdefined();
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}
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if (isNotConstant()) {
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if (RHS.isConstant()) {
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if (Val == RHS.Val)
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return markOverdefined();
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// Unless we can prove that the two Constants are different, we must
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// move to overdefined.
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// FIXME: use TargetData for smarter constant folding.
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if (ConstantInt *Res = dyn_cast<ConstantInt>(
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ConstantFoldCompareInstOperands(CmpInst::ICMP_NE,
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getNotConstant(),
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RHS.getConstant())))
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if (Res->isOne())
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return false;
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return markOverdefined();
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}
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if (RHS.isNotConstant()) {
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if (Val == RHS.Val)
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return false;
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return markOverdefined();
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}
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return markOverdefined();
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}
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assert(isConstantRange() && "New LVILattice type?");
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if (!RHS.isConstantRange())
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return markOverdefined();
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ConstantRange NewR = Range.unionWith(RHS.getConstantRange());
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if (NewR.isFullSet())
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return markOverdefined();
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return markConstantRange(NewR);
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}
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};
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} // end anonymous namespace.
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namespace llvm {
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raw_ostream &operator<<(raw_ostream &OS, const LVILatticeVal &Val)
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LLVM_ATTRIBUTE_USED;
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raw_ostream &operator<<(raw_ostream &OS, const LVILatticeVal &Val) {
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if (Val.isUndefined())
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return OS << "undefined";
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if (Val.isOverdefined())
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return OS << "overdefined";
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if (Val.isNotConstant())
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return OS << "notconstant<" << *Val.getNotConstant() << '>';
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else if (Val.isConstantRange())
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return OS << "constantrange<" << Val.getConstantRange().getLower() << ", "
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<< Val.getConstantRange().getUpper() << '>';
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return OS << "constant<" << *Val.getConstant() << '>';
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}
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}
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//===----------------------------------------------------------------------===//
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// LazyValueInfoCache Decl
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//===----------------------------------------------------------------------===//
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namespace {
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/// LVIValueHandle - A callback value handle update the cache when
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/// values are erased.
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class LazyValueInfoCache;
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struct LVIValueHandle : public CallbackVH {
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LazyValueInfoCache *Parent;
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LVIValueHandle(Value *V, LazyValueInfoCache *P)
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: CallbackVH(V), Parent(P) { }
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void deleted();
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void allUsesReplacedWith(Value *V) {
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deleted();
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}
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};
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}
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namespace llvm {
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template<>
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struct DenseMapInfo<LVIValueHandle> {
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typedef DenseMapInfo<Value*> PointerInfo;
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static inline LVIValueHandle getEmptyKey() {
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return LVIValueHandle(PointerInfo::getEmptyKey(),
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static_cast<LazyValueInfoCache*>(0));
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}
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static inline LVIValueHandle getTombstoneKey() {
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return LVIValueHandle(PointerInfo::getTombstoneKey(),
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static_cast<LazyValueInfoCache*>(0));
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}
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static unsigned getHashValue(const LVIValueHandle &Val) {
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return PointerInfo::getHashValue(Val);
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}
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static bool isEqual(const LVIValueHandle &LHS, const LVIValueHandle &RHS) {
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return LHS == RHS;
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}
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};
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template<>
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struct DenseMapInfo<std::pair<AssertingVH<BasicBlock>, Value*> > {
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typedef std::pair<AssertingVH<BasicBlock>, Value*> PairTy;
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typedef DenseMapInfo<AssertingVH<BasicBlock> > APointerInfo;
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typedef DenseMapInfo<Value*> BPointerInfo;
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static inline PairTy getEmptyKey() {
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return std::make_pair(APointerInfo::getEmptyKey(),
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BPointerInfo::getEmptyKey());
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}
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static inline PairTy getTombstoneKey() {
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return std::make_pair(APointerInfo::getTombstoneKey(),
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BPointerInfo::getTombstoneKey());
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}
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static unsigned getHashValue( const PairTy &Val) {
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return APointerInfo::getHashValue(Val.first) ^
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BPointerInfo::getHashValue(Val.second);
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}
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static bool isEqual(const PairTy &LHS, const PairTy &RHS) {
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return APointerInfo::isEqual(LHS.first, RHS.first) &&
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BPointerInfo::isEqual(LHS.second, RHS.second);
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}
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};
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}
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namespace {
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/// LazyValueInfoCache - This is the cache kept by LazyValueInfo which
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/// maintains information about queries across the clients' queries.
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class LazyValueInfoCache {
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/// ValueCacheEntryTy - This is all of the cached block information for
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/// exactly one Value*. The entries are sorted by the BasicBlock* of the
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/// entries, allowing us to do a lookup with a binary search.
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typedef std::map<AssertingVH<BasicBlock>, LVILatticeVal> ValueCacheEntryTy;
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/// ValueCache - This is all of the cached information for all values,
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/// mapped from Value* to key information.
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DenseMap<LVIValueHandle, ValueCacheEntryTy> ValueCache;
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/// OverDefinedCache - This tracks, on a per-block basis, the set of
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/// values that are over-defined at the end of that block. This is required
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/// for cache updating.
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typedef std::pair<AssertingVH<BasicBlock>, Value*> OverDefinedPairTy;
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DenseSet<OverDefinedPairTy> OverDefinedCache;
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/// BlockValueStack - This stack holds the state of the value solver
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/// during a query. It basically emulates the callstack of the naive
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/// recursive value lookup process.
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std::stack<std::pair<BasicBlock*, Value*> > BlockValueStack;
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friend struct LVIValueHandle;
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/// OverDefinedCacheUpdater - A helper object that ensures that the
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/// OverDefinedCache is updated whenever solveBlockValue returns.
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struct OverDefinedCacheUpdater {
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LazyValueInfoCache *Parent;
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Value *Val;
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BasicBlock *BB;
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LVILatticeVal &BBLV;
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OverDefinedCacheUpdater(Value *V, BasicBlock *B, LVILatticeVal &LV,
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LazyValueInfoCache *P)
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: Parent(P), Val(V), BB(B), BBLV(LV) { }
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bool markResult(bool changed) {
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if (changed && BBLV.isOverdefined())
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Parent->OverDefinedCache.insert(std::make_pair(BB, Val));
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return changed;
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}
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};
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LVILatticeVal getBlockValue(Value *Val, BasicBlock *BB);
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bool getEdgeValue(Value *V, BasicBlock *F, BasicBlock *T,
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LVILatticeVal &Result);
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bool hasBlockValue(Value *Val, BasicBlock *BB);
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// These methods process one work item and may add more. A false value
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// returned means that the work item was not completely processed and must
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// be revisited after going through the new items.
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bool solveBlockValue(Value *Val, BasicBlock *BB);
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bool solveBlockValueNonLocal(LVILatticeVal &BBLV,
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Value *Val, BasicBlock *BB);
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bool solveBlockValuePHINode(LVILatticeVal &BBLV,
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PHINode *PN, BasicBlock *BB);
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bool solveBlockValueConstantRange(LVILatticeVal &BBLV,
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Instruction *BBI, BasicBlock *BB);
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void solve();
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ValueCacheEntryTy &lookup(Value *V) {
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return ValueCache[LVIValueHandle(V, this)];
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}
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public:
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/// getValueInBlock - This is the query interface to determine the lattice
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/// value for the specified Value* at the end of the specified block.
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LVILatticeVal getValueInBlock(Value *V, BasicBlock *BB);
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/// getValueOnEdge - This is the query interface to determine the lattice
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/// value for the specified Value* that is true on the specified edge.
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LVILatticeVal getValueOnEdge(Value *V, BasicBlock *FromBB,BasicBlock *ToBB);
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/// threadEdge - This is the update interface to inform the cache that an
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/// edge from PredBB to OldSucc has been threaded to be from PredBB to
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/// NewSucc.
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void threadEdge(BasicBlock *PredBB,BasicBlock *OldSucc,BasicBlock *NewSucc);
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/// eraseBlock - This is part of the update interface to inform the cache
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/// that a block has been deleted.
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void eraseBlock(BasicBlock *BB);
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/// clear - Empty the cache.
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void clear() {
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ValueCache.clear();
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OverDefinedCache.clear();
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}
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};
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} // end anonymous namespace
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void LVIValueHandle::deleted() {
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typedef std::pair<AssertingVH<BasicBlock>, Value*> OverDefinedPairTy;
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SmallVector<OverDefinedPairTy, 4> ToErase;
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for (DenseSet<OverDefinedPairTy>::iterator
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I = Parent->OverDefinedCache.begin(),
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E = Parent->OverDefinedCache.end();
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I != E; ++I) {
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if (I->second == getValPtr())
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ToErase.push_back(*I);
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}
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for (SmallVector<OverDefinedPairTy, 4>::iterator I = ToErase.begin(),
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E = ToErase.end(); I != E; ++I)
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Parent->OverDefinedCache.erase(*I);
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// This erasure deallocates *this, so it MUST happen after we're done
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// using any and all members of *this.
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Parent->ValueCache.erase(*this);
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}
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void LazyValueInfoCache::eraseBlock(BasicBlock *BB) {
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SmallVector<OverDefinedPairTy, 4> ToErase;
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for (DenseSet<OverDefinedPairTy>::iterator I = OverDefinedCache.begin(),
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E = OverDefinedCache.end(); I != E; ++I) {
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if (I->first == BB)
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ToErase.push_back(*I);
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}
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for (SmallVector<OverDefinedPairTy, 4>::iterator I = ToErase.begin(),
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E = ToErase.end(); I != E; ++I)
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OverDefinedCache.erase(*I);
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for (DenseMap<LVIValueHandle, ValueCacheEntryTy>::iterator
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I = ValueCache.begin(), E = ValueCache.end(); I != E; ++I)
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I->second.erase(BB);
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}
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void LazyValueInfoCache::solve() {
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while (!BlockValueStack.empty()) {
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std::pair<BasicBlock*, Value*> &e = BlockValueStack.top();
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if (solveBlockValue(e.second, e.first))
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BlockValueStack.pop();
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}
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}
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bool LazyValueInfoCache::hasBlockValue(Value *Val, BasicBlock *BB) {
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// If already a constant, there is nothing to compute.
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if (isa<Constant>(Val))
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return true;
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LVIValueHandle ValHandle(Val, this);
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if (!ValueCache.count(ValHandle)) return false;
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return ValueCache[ValHandle].count(BB);
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}
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LVILatticeVal LazyValueInfoCache::getBlockValue(Value *Val, BasicBlock *BB) {
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// If already a constant, there is nothing to compute.
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if (Constant *VC = dyn_cast<Constant>(Val))
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return LVILatticeVal::get(VC);
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return lookup(Val)[BB];
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}
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bool LazyValueInfoCache::solveBlockValue(Value *Val, BasicBlock *BB) {
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if (isa<Constant>(Val))
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return true;
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ValueCacheEntryTy &Cache = lookup(Val);
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LVILatticeVal &BBLV = Cache[BB];
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// OverDefinedCacheUpdater is a helper object that will update
|
|
// the OverDefinedCache for us when this method exits. Make sure to
|
|
// call markResult on it as we exist, passing a bool to indicate if the
|
|
// cache needs updating, i.e. if we have solve a new value or not.
|
|
OverDefinedCacheUpdater ODCacheUpdater(Val, BB, BBLV, this);
|
|
|
|
// If we've already computed this block's value, return it.
|
|
if (!BBLV.isUndefined()) {
|
|
DEBUG(dbgs() << " reuse BB '" << BB->getName() << "' val=" << BBLV <<'\n');
|
|
|
|
// Since we're reusing a cached value here, we don't need to update the
|
|
// OverDefinedCahce. The cache will have been properly updated
|
|
// whenever the cached value was inserted.
|
|
ODCacheUpdater.markResult(false);
|
|
return true;
|
|
}
|
|
|
|
// Otherwise, this is the first time we're seeing this block. Reset the
|
|
// lattice value to overdefined, so that cycles will terminate and be
|
|
// conservatively correct.
|
|
BBLV.markOverdefined();
|
|
|
|
Instruction *BBI = dyn_cast<Instruction>(Val);
|
|
if (BBI == 0 || BBI->getParent() != BB) {
|
|
return ODCacheUpdater.markResult(solveBlockValueNonLocal(BBLV, Val, BB));
|
|
}
|
|
|
|
if (PHINode *PN = dyn_cast<PHINode>(BBI)) {
|
|
return ODCacheUpdater.markResult(solveBlockValuePHINode(BBLV, PN, BB));
|
|
}
|
|
|
|
if (AllocaInst *AI = dyn_cast<AllocaInst>(BBI)) {
|
|
BBLV = LVILatticeVal::getNot(ConstantPointerNull::get(AI->getType()));
|
|
return ODCacheUpdater.markResult(true);
|
|
}
|
|
|
|
// We can only analyze the definitions of certain classes of instructions
|
|
// (integral binops and casts at the moment), so bail if this isn't one.
|
|
LVILatticeVal Result;
|
|
if ((!isa<BinaryOperator>(BBI) && !isa<CastInst>(BBI)) ||
|
|
!BBI->getType()->isIntegerTy()) {
|
|
DEBUG(dbgs() << " compute BB '" << BB->getName()
|
|
<< "' - overdefined because inst def found.\n");
|
|
BBLV.markOverdefined();
|
|
return ODCacheUpdater.markResult(true);
|
|
}
|
|
|
|
// FIXME: We're currently limited to binops with a constant RHS. This should
|
|
// be improved.
|
|
BinaryOperator *BO = dyn_cast<BinaryOperator>(BBI);
|
|
if (BO && !isa<ConstantInt>(BO->getOperand(1))) {
|
|
DEBUG(dbgs() << " compute BB '" << BB->getName()
|
|
<< "' - overdefined because inst def found.\n");
|
|
|
|
BBLV.markOverdefined();
|
|
return ODCacheUpdater.markResult(true);
|
|
}
|
|
|
|
return ODCacheUpdater.markResult(solveBlockValueConstantRange(BBLV, BBI, BB));
|
|
}
|
|
|
|
static bool InstructionDereferencesPointer(Instruction *I, Value *Ptr) {
|
|
if (LoadInst *L = dyn_cast<LoadInst>(I)) {
|
|
return L->getPointerAddressSpace() == 0 &&
|
|
GetUnderlyingObject(L->getPointerOperand()) ==
|
|
GetUnderlyingObject(Ptr);
|
|
}
|
|
if (StoreInst *S = dyn_cast<StoreInst>(I)) {
|
|
return S->getPointerAddressSpace() == 0 &&
|
|
GetUnderlyingObject(S->getPointerOperand()) ==
|
|
GetUnderlyingObject(Ptr);
|
|
}
|
|
if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(I)) {
|
|
if (MI->isVolatile()) return false;
|
|
|
|
// FIXME: check whether it has a valuerange that excludes zero?
|
|
ConstantInt *Len = dyn_cast<ConstantInt>(MI->getLength());
|
|
if (!Len || Len->isZero()) return false;
|
|
|
|
if (MI->getDestAddressSpace() == 0)
|
|
if (MI->getRawDest() == Ptr || MI->getDest() == Ptr)
|
|
return true;
|
|
if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI))
|
|
if (MTI->getSourceAddressSpace() == 0)
|
|
if (MTI->getRawSource() == Ptr || MTI->getSource() == Ptr)
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
bool LazyValueInfoCache::solveBlockValueNonLocal(LVILatticeVal &BBLV,
|
|
Value *Val, BasicBlock *BB) {
|
|
LVILatticeVal Result; // Start Undefined.
|
|
|
|
// If this is a pointer, and there's a load from that pointer in this BB,
|
|
// then we know that the pointer can't be NULL.
|
|
bool NotNull = false;
|
|
if (Val->getType()->isPointerTy()) {
|
|
if (isa<AllocaInst>(Val)) {
|
|
NotNull = true;
|
|
} else {
|
|
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();BI != BE;++BI){
|
|
if (InstructionDereferencesPointer(BI, Val)) {
|
|
NotNull = true;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// If this is the entry block, we must be asking about an argument. The
|
|
// value is overdefined.
|
|
if (BB == &BB->getParent()->getEntryBlock()) {
|
|
assert(isa<Argument>(Val) && "Unknown live-in to the entry block");
|
|
if (NotNull) {
|
|
PointerType *PTy = cast<PointerType>(Val->getType());
|
|
Result = LVILatticeVal::getNot(ConstantPointerNull::get(PTy));
|
|
} else {
|
|
Result.markOverdefined();
|
|
}
|
|
BBLV = Result;
|
|
return true;
|
|
}
|
|
|
|
// Loop over all of our predecessors, merging what we know from them into
|
|
// result.
|
|
bool EdgesMissing = false;
|
|
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
|
|
LVILatticeVal EdgeResult;
|
|
EdgesMissing |= !getEdgeValue(Val, *PI, BB, EdgeResult);
|
|
if (EdgesMissing)
|
|
continue;
|
|
|
|
Result.mergeIn(EdgeResult);
|
|
|
|
// If we hit overdefined, exit early. The BlockVals entry is already set
|
|
// to overdefined.
|
|
if (Result.isOverdefined()) {
|
|
DEBUG(dbgs() << " compute BB '" << BB->getName()
|
|
<< "' - overdefined because of pred.\n");
|
|
// If we previously determined that this is a pointer that can't be null
|
|
// then return that rather than giving up entirely.
|
|
if (NotNull) {
|
|
PointerType *PTy = cast<PointerType>(Val->getType());
|
|
Result = LVILatticeVal::getNot(ConstantPointerNull::get(PTy));
|
|
}
|
|
|
|
BBLV = Result;
|
|
return true;
|
|
}
|
|
}
|
|
if (EdgesMissing)
|
|
return false;
|
|
|
|
// Return the merged value, which is more precise than 'overdefined'.
|
|
assert(!Result.isOverdefined());
|
|
BBLV = Result;
|
|
return true;
|
|
}
|
|
|
|
bool LazyValueInfoCache::solveBlockValuePHINode(LVILatticeVal &BBLV,
|
|
PHINode *PN, BasicBlock *BB) {
|
|
LVILatticeVal Result; // Start Undefined.
|
|
|
|
// Loop over all of our predecessors, merging what we know from them into
|
|
// result.
|
|
bool EdgesMissing = false;
|
|
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
|
|
BasicBlock *PhiBB = PN->getIncomingBlock(i);
|
|
Value *PhiVal = PN->getIncomingValue(i);
|
|
LVILatticeVal EdgeResult;
|
|
EdgesMissing |= !getEdgeValue(PhiVal, PhiBB, BB, EdgeResult);
|
|
if (EdgesMissing)
|
|
continue;
|
|
|
|
Result.mergeIn(EdgeResult);
|
|
|
|
// If we hit overdefined, exit early. The BlockVals entry is already set
|
|
// to overdefined.
|
|
if (Result.isOverdefined()) {
|
|
DEBUG(dbgs() << " compute BB '" << BB->getName()
|
|
<< "' - overdefined because of pred.\n");
|
|
|
|
BBLV = Result;
|
|
return true;
|
|
}
|
|
}
|
|
if (EdgesMissing)
|
|
return false;
|
|
|
|
// Return the merged value, which is more precise than 'overdefined'.
|
|
assert(!Result.isOverdefined() && "Possible PHI in entry block?");
|
|
BBLV = Result;
|
|
return true;
|
|
}
|
|
|
|
bool LazyValueInfoCache::solveBlockValueConstantRange(LVILatticeVal &BBLV,
|
|
Instruction *BBI,
|
|
BasicBlock *BB) {
|
|
// Figure out the range of the LHS. If that fails, bail.
|
|
if (!hasBlockValue(BBI->getOperand(0), BB)) {
|
|
BlockValueStack.push(std::make_pair(BB, BBI->getOperand(0)));
|
|
return false;
|
|
}
|
|
|
|
LVILatticeVal LHSVal = getBlockValue(BBI->getOperand(0), BB);
|
|
if (!LHSVal.isConstantRange()) {
|
|
BBLV.markOverdefined();
|
|
return true;
|
|
}
|
|
|
|
ConstantRange LHSRange = LHSVal.getConstantRange();
|
|
ConstantRange RHSRange(1);
|
|
IntegerType *ResultTy = cast<IntegerType>(BBI->getType());
|
|
if (isa<BinaryOperator>(BBI)) {
|
|
if (ConstantInt *RHS = dyn_cast<ConstantInt>(BBI->getOperand(1))) {
|
|
RHSRange = ConstantRange(RHS->getValue());
|
|
} else {
|
|
BBLV.markOverdefined();
|
|
return true;
|
|
}
|
|
}
|
|
|
|
// NOTE: We're currently limited by the set of operations that ConstantRange
|
|
// can evaluate symbolically. Enhancing that set will allows us to analyze
|
|
// more definitions.
|
|
LVILatticeVal Result;
|
|
switch (BBI->getOpcode()) {
|
|
case Instruction::Add:
|
|
Result.markConstantRange(LHSRange.add(RHSRange));
|
|
break;
|
|
case Instruction::Sub:
|
|
Result.markConstantRange(LHSRange.sub(RHSRange));
|
|
break;
|
|
case Instruction::Mul:
|
|
Result.markConstantRange(LHSRange.multiply(RHSRange));
|
|
break;
|
|
case Instruction::UDiv:
|
|
Result.markConstantRange(LHSRange.udiv(RHSRange));
|
|
break;
|
|
case Instruction::Shl:
|
|
Result.markConstantRange(LHSRange.shl(RHSRange));
|
|
break;
|
|
case Instruction::LShr:
|
|
Result.markConstantRange(LHSRange.lshr(RHSRange));
|
|
break;
|
|
case Instruction::Trunc:
|
|
Result.markConstantRange(LHSRange.truncate(ResultTy->getBitWidth()));
|
|
break;
|
|
case Instruction::SExt:
|
|
Result.markConstantRange(LHSRange.signExtend(ResultTy->getBitWidth()));
|
|
break;
|
|
case Instruction::ZExt:
|
|
Result.markConstantRange(LHSRange.zeroExtend(ResultTy->getBitWidth()));
|
|
break;
|
|
case Instruction::BitCast:
|
|
Result.markConstantRange(LHSRange);
|
|
break;
|
|
case Instruction::And:
|
|
Result.markConstantRange(LHSRange.binaryAnd(RHSRange));
|
|
break;
|
|
case Instruction::Or:
|
|
Result.markConstantRange(LHSRange.binaryOr(RHSRange));
|
|
break;
|
|
|
|
// Unhandled instructions are overdefined.
|
|
default:
|
|
DEBUG(dbgs() << " compute BB '" << BB->getName()
|
|
<< "' - overdefined because inst def found.\n");
|
|
Result.markOverdefined();
|
|
break;
|
|
}
|
|
|
|
BBLV = Result;
|
|
return true;
|
|
}
|
|
|
|
/// getEdgeValue - This method attempts to infer more complex
|
|
bool LazyValueInfoCache::getEdgeValue(Value *Val, BasicBlock *BBFrom,
|
|
BasicBlock *BBTo, LVILatticeVal &Result) {
|
|
// If already a constant, there is nothing to compute.
|
|
if (Constant *VC = dyn_cast<Constant>(Val)) {
|
|
Result = LVILatticeVal::get(VC);
|
|
return true;
|
|
}
|
|
|
|
// TODO: Handle more complex conditionals. If (v == 0 || v2 < 1) is false, we
|
|
// know that v != 0.
|
|
if (BranchInst *BI = dyn_cast<BranchInst>(BBFrom->getTerminator())) {
|
|
// If this is a conditional branch and only one successor goes to BBTo, then
|
|
// we maybe able to infer something from the condition.
|
|
if (BI->isConditional() &&
|
|
BI->getSuccessor(0) != BI->getSuccessor(1)) {
|
|
bool isTrueDest = BI->getSuccessor(0) == BBTo;
|
|
assert(BI->getSuccessor(!isTrueDest) == BBTo &&
|
|
"BBTo isn't a successor of BBFrom");
|
|
|
|
// If V is the condition of the branch itself, then we know exactly what
|
|
// it is.
|
|
if (BI->getCondition() == Val) {
|
|
Result = LVILatticeVal::get(ConstantInt::get(
|
|
Type::getInt1Ty(Val->getContext()), isTrueDest));
|
|
return true;
|
|
}
|
|
|
|
// If the condition of the branch is an equality comparison, we may be
|
|
// able to infer the value.
|
|
ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition());
|
|
if (ICI && ICI->getOperand(0) == Val &&
|
|
isa<Constant>(ICI->getOperand(1))) {
|
|
if (ICI->isEquality()) {
|
|
// We know that V has the RHS constant if this is a true SETEQ or
|
|
// false SETNE.
|
|
if (isTrueDest == (ICI->getPredicate() == ICmpInst::ICMP_EQ))
|
|
Result = LVILatticeVal::get(cast<Constant>(ICI->getOperand(1)));
|
|
else
|
|
Result = LVILatticeVal::getNot(cast<Constant>(ICI->getOperand(1)));
|
|
return true;
|
|
}
|
|
|
|
if (ConstantInt *CI = dyn_cast<ConstantInt>(ICI->getOperand(1))) {
|
|
// Calculate the range of values that would satisfy the comparison.
|
|
ConstantRange CmpRange(CI->getValue(), CI->getValue()+1);
|
|
ConstantRange TrueValues =
|
|
ConstantRange::makeICmpRegion(ICI->getPredicate(), CmpRange);
|
|
|
|
// If we're interested in the false dest, invert the condition.
|
|
if (!isTrueDest) TrueValues = TrueValues.inverse();
|
|
|
|
// Figure out the possible values of the query BEFORE this branch.
|
|
if (!hasBlockValue(Val, BBFrom)) {
|
|
BlockValueStack.push(std::make_pair(BBFrom, Val));
|
|
return false;
|
|
}
|
|
|
|
LVILatticeVal InBlock = getBlockValue(Val, BBFrom);
|
|
if (!InBlock.isConstantRange()) {
|
|
Result = LVILatticeVal::getRange(TrueValues);
|
|
return true;
|
|
}
|
|
|
|
// Find all potential values that satisfy both the input and output
|
|
// conditions.
|
|
ConstantRange PossibleValues =
|
|
TrueValues.intersectWith(InBlock.getConstantRange());
|
|
|
|
Result = LVILatticeVal::getRange(PossibleValues);
|
|
return true;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// If the edge was formed by a switch on the value, then we may know exactly
|
|
// what it is.
|
|
if (SwitchInst *SI = dyn_cast<SwitchInst>(BBFrom->getTerminator())) {
|
|
if (SI->getCondition() == Val) {
|
|
// We don't know anything in the default case.
|
|
if (SI->getDefaultDest() == BBTo) {
|
|
Result.markOverdefined();
|
|
return true;
|
|
}
|
|
|
|
// We only know something if there is exactly one value that goes from
|
|
// BBFrom to BBTo.
|
|
unsigned NumEdges = 0;
|
|
ConstantInt *EdgeVal = 0;
|
|
for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i) {
|
|
if (SI->getSuccessor(i) != BBTo) continue;
|
|
if (NumEdges++) break;
|
|
EdgeVal = SI->getCaseValue(i);
|
|
}
|
|
assert(EdgeVal && "Missing successor?");
|
|
if (NumEdges == 1) {
|
|
Result = LVILatticeVal::get(EdgeVal);
|
|
return true;
|
|
}
|
|
}
|
|
}
|
|
|
|
// Otherwise see if the value is known in the block.
|
|
if (hasBlockValue(Val, BBFrom)) {
|
|
Result = getBlockValue(Val, BBFrom);
|
|
return true;
|
|
}
|
|
BlockValueStack.push(std::make_pair(BBFrom, Val));
|
|
return false;
|
|
}
|
|
|
|
LVILatticeVal LazyValueInfoCache::getValueInBlock(Value *V, BasicBlock *BB) {
|
|
DEBUG(dbgs() << "LVI Getting block end value " << *V << " at '"
|
|
<< BB->getName() << "'\n");
|
|
|
|
BlockValueStack.push(std::make_pair(BB, V));
|
|
solve();
|
|
LVILatticeVal Result = getBlockValue(V, BB);
|
|
|
|
DEBUG(dbgs() << " Result = " << Result << "\n");
|
|
return Result;
|
|
}
|
|
|
|
LVILatticeVal LazyValueInfoCache::
|
|
getValueOnEdge(Value *V, BasicBlock *FromBB, BasicBlock *ToBB) {
|
|
DEBUG(dbgs() << "LVI Getting edge value " << *V << " from '"
|
|
<< FromBB->getName() << "' to '" << ToBB->getName() << "'\n");
|
|
|
|
LVILatticeVal Result;
|
|
if (!getEdgeValue(V, FromBB, ToBB, Result)) {
|
|
solve();
|
|
bool WasFastQuery = getEdgeValue(V, FromBB, ToBB, Result);
|
|
(void)WasFastQuery;
|
|
assert(WasFastQuery && "More work to do after problem solved?");
|
|
}
|
|
|
|
DEBUG(dbgs() << " Result = " << Result << "\n");
|
|
return Result;
|
|
}
|
|
|
|
void LazyValueInfoCache::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
|
|
BasicBlock *NewSucc) {
|
|
// When an edge in the graph has been threaded, values that we could not
|
|
// determine a value for before (i.e. were marked overdefined) may be possible
|
|
// to solve now. We do NOT try to proactively update these values. Instead,
|
|
// we clear their entries from the cache, and allow lazy updating to recompute
|
|
// them when needed.
|
|
|
|
// The updating process is fairly simple: we need to dropped cached info
|
|
// for all values that were marked overdefined in OldSucc, and for those same
|
|
// values in any successor of OldSucc (except NewSucc) in which they were
|
|
// also marked overdefined.
|
|
std::vector<BasicBlock*> worklist;
|
|
worklist.push_back(OldSucc);
|
|
|
|
DenseSet<Value*> ClearSet;
|
|
for (DenseSet<OverDefinedPairTy>::iterator I = OverDefinedCache.begin(),
|
|
E = OverDefinedCache.end(); I != E; ++I) {
|
|
if (I->first == OldSucc)
|
|
ClearSet.insert(I->second);
|
|
}
|
|
|
|
// Use a worklist to perform a depth-first search of OldSucc's successors.
|
|
// NOTE: We do not need a visited list since any blocks we have already
|
|
// visited will have had their overdefined markers cleared already, and we
|
|
// thus won't loop to their successors.
|
|
while (!worklist.empty()) {
|
|
BasicBlock *ToUpdate = worklist.back();
|
|
worklist.pop_back();
|
|
|
|
// Skip blocks only accessible through NewSucc.
|
|
if (ToUpdate == NewSucc) continue;
|
|
|
|
bool changed = false;
|
|
for (DenseSet<Value*>::iterator I = ClearSet.begin(), E = ClearSet.end();
|
|
I != E; ++I) {
|
|
// If a value was marked overdefined in OldSucc, and is here too...
|
|
DenseSet<OverDefinedPairTy>::iterator OI =
|
|
OverDefinedCache.find(std::make_pair(ToUpdate, *I));
|
|
if (OI == OverDefinedCache.end()) continue;
|
|
|
|
// Remove it from the caches.
|
|
ValueCacheEntryTy &Entry = ValueCache[LVIValueHandle(*I, this)];
|
|
ValueCacheEntryTy::iterator CI = Entry.find(ToUpdate);
|
|
|
|
assert(CI != Entry.end() && "Couldn't find entry to update?");
|
|
Entry.erase(CI);
|
|
OverDefinedCache.erase(OI);
|
|
|
|
// If we removed anything, then we potentially need to update
|
|
// blocks successors too.
|
|
changed = true;
|
|
}
|
|
|
|
if (!changed) continue;
|
|
|
|
worklist.insert(worklist.end(), succ_begin(ToUpdate), succ_end(ToUpdate));
|
|
}
|
|
}
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// LazyValueInfo Impl
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
/// getCache - This lazily constructs the LazyValueInfoCache.
|
|
static LazyValueInfoCache &getCache(void *&PImpl) {
|
|
if (!PImpl)
|
|
PImpl = new LazyValueInfoCache();
|
|
return *static_cast<LazyValueInfoCache*>(PImpl);
|
|
}
|
|
|
|
bool LazyValueInfo::runOnFunction(Function &F) {
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if (PImpl)
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getCache(PImpl).clear();
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TD = getAnalysisIfAvailable<TargetData>();
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// Fully lazy.
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return false;
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}
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void LazyValueInfo::releaseMemory() {
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// If the cache was allocated, free it.
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if (PImpl) {
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delete &getCache(PImpl);
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PImpl = 0;
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}
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}
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Constant *LazyValueInfo::getConstant(Value *V, BasicBlock *BB) {
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LVILatticeVal Result = getCache(PImpl).getValueInBlock(V, BB);
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if (Result.isConstant())
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return Result.getConstant();
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if (Result.isConstantRange()) {
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ConstantRange CR = Result.getConstantRange();
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if (const APInt *SingleVal = CR.getSingleElement())
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return ConstantInt::get(V->getContext(), *SingleVal);
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}
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return 0;
|
|
}
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|
|
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/// getConstantOnEdge - Determine whether the specified value is known to be a
|
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/// constant on the specified edge. Return null if not.
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Constant *LazyValueInfo::getConstantOnEdge(Value *V, BasicBlock *FromBB,
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BasicBlock *ToBB) {
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LVILatticeVal Result = getCache(PImpl).getValueOnEdge(V, FromBB, ToBB);
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|
|
|
if (Result.isConstant())
|
|
return Result.getConstant();
|
|
if (Result.isConstantRange()) {
|
|
ConstantRange CR = Result.getConstantRange();
|
|
if (const APInt *SingleVal = CR.getSingleElement())
|
|
return ConstantInt::get(V->getContext(), *SingleVal);
|
|
}
|
|
return 0;
|
|
}
|
|
|
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/// getPredicateOnEdge - Determine whether the specified value comparison
|
|
/// with a constant is known to be true or false on the specified CFG edge.
|
|
/// Pred is a CmpInst predicate.
|
|
LazyValueInfo::Tristate
|
|
LazyValueInfo::getPredicateOnEdge(unsigned Pred, Value *V, Constant *C,
|
|
BasicBlock *FromBB, BasicBlock *ToBB) {
|
|
LVILatticeVal Result = getCache(PImpl).getValueOnEdge(V, FromBB, ToBB);
|
|
|
|
// If we know the value is a constant, evaluate the conditional.
|
|
Constant *Res = 0;
|
|
if (Result.isConstant()) {
|
|
Res = ConstantFoldCompareInstOperands(Pred, Result.getConstant(), C, TD);
|
|
if (ConstantInt *ResCI = dyn_cast<ConstantInt>(Res))
|
|
return ResCI->isZero() ? False : True;
|
|
return Unknown;
|
|
}
|
|
|
|
if (Result.isConstantRange()) {
|
|
ConstantInt *CI = dyn_cast<ConstantInt>(C);
|
|
if (!CI) return Unknown;
|
|
|
|
ConstantRange CR = Result.getConstantRange();
|
|
if (Pred == ICmpInst::ICMP_EQ) {
|
|
if (!CR.contains(CI->getValue()))
|
|
return False;
|
|
|
|
if (CR.isSingleElement() && CR.contains(CI->getValue()))
|
|
return True;
|
|
} else if (Pred == ICmpInst::ICMP_NE) {
|
|
if (!CR.contains(CI->getValue()))
|
|
return True;
|
|
|
|
if (CR.isSingleElement() && CR.contains(CI->getValue()))
|
|
return False;
|
|
}
|
|
|
|
// Handle more complex predicates.
|
|
ConstantRange TrueValues =
|
|
ICmpInst::makeConstantRange((ICmpInst::Predicate)Pred, CI->getValue());
|
|
if (TrueValues.contains(CR))
|
|
return True;
|
|
if (TrueValues.inverse().contains(CR))
|
|
return False;
|
|
return Unknown;
|
|
}
|
|
|
|
if (Result.isNotConstant()) {
|
|
// If this is an equality comparison, we can try to fold it knowing that
|
|
// "V != C1".
|
|
if (Pred == ICmpInst::ICMP_EQ) {
|
|
// !C1 == C -> false iff C1 == C.
|
|
Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
|
|
Result.getNotConstant(), C, TD);
|
|
if (Res->isNullValue())
|
|
return False;
|
|
} else if (Pred == ICmpInst::ICMP_NE) {
|
|
// !C1 != C -> true iff C1 == C.
|
|
Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
|
|
Result.getNotConstant(), C, TD);
|
|
if (Res->isNullValue())
|
|
return True;
|
|
}
|
|
return Unknown;
|
|
}
|
|
|
|
return Unknown;
|
|
}
|
|
|
|
void LazyValueInfo::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
|
|
BasicBlock *NewSucc) {
|
|
if (PImpl) getCache(PImpl).threadEdge(PredBB, OldSucc, NewSucc);
|
|
}
|
|
|
|
void LazyValueInfo::eraseBlock(BasicBlock *BB) {
|
|
if (PImpl) getCache(PImpl).eraseBlock(BB);
|
|
}
|