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limit the recursion depth of GetLinearExpression. This

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fixes a crash analyzing consumer-lame, which had an "%X = add %X, 1"
in unreachable code.

llvm-svn: 90000
This commit is contained in:
Chris Lattner 2009-11-27 08:32:52 +00:00
parent a466dbe80a
commit e7056c8cde
1 changed files with 13 additions and 6 deletions
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19
lib/Analysis/ValueTracking.cpp
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@ -955,8 +955,15 @@ bool llvm::CannotBeNegativeZero(const Value *V, unsigned Depth) {
/// have IntegerType. Note that this looks through extends, so the high bits
/// may not be represented in the result.
static Value *GetLinearExpression(Value *V, APInt &Scale, APInt &Offset,
const TargetData *TD) {
const TargetData *TD, unsigned Depth) {
assert(isa<IntegerType>(V->getType()) && "Not an integer value");
// Limit our recursion depth.
if (Depth == 6) {
Scale = 1;
Offset = 0;
return V;
}
if (BinaryOperator *BOp = dyn_cast<BinaryOperator>(V)) {
if (ConstantInt *RHSC = dyn_cast<ConstantInt>(BOp->getOperand(1))) {
@ -969,16 +976,16 @@ static Value *GetLinearExpression(Value *V, APInt &Scale, APInt &Offset,
break;
// FALL THROUGH.
case Instruction::Add:
V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, TD);
V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, TD, Depth+1);
Offset += RHSC->getValue();
return V;
case Instruction::Mul:
V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, TD);
V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, TD, Depth+1);
Offset *= RHSC->getValue();
Scale *= RHSC->getValue();
return V;
case Instruction::Shl:
V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, TD);
V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, TD, Depth+1);
Offset <<= RHSC->getValue().getLimitedValue();
Scale <<= RHSC->getValue().getLimitedValue();
return V;
@ -994,7 +1001,7 @@ static Value *GetLinearExpression(Value *V, APInt &Scale, APInt &Offset,
unsigned SmallWidth = CastOp->getType()->getPrimitiveSizeInBits();
Scale.trunc(SmallWidth);
Offset.trunc(SmallWidth);
Value *Result = GetLinearExpression(CastOp, Scale, Offset, TD);
Value *Result = GetLinearExpression(CastOp, Scale, Offset, TD, Depth+1);
Scale.zext(OldWidth);
Offset.zext(OldWidth);
return Result;
@ -1088,7 +1095,7 @@ const Value *llvm::DecomposeGEPExpression(const Value *V, int64_t &BaseOffs,
// Use GetLinearExpression to decompose the index into a C1*V+C2 form.
unsigned Width = cast<IntegerType>(Index->getType())->getBitWidth();
APInt IndexScale(Width, 0), IndexOffset(Width, 0);
Index = GetLinearExpression(Index, IndexScale, IndexOffset, TD);
Index = GetLinearExpression(Index, IndexScale, IndexOffset, TD, 0);
// The GEP index scale ("Scale") scales C1*V+C2, yielding (C1*V+C2)*Scale.
// This gives us an aggregate computation of (C1*Scale)*V + C2*Scale.