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Implement PR1143 (at -m64) by making basicaa look through extensions. We

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previously already handled it at -m32 because there were no i32->i64 
extensions for addressing.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@89959 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2009-11-26 18:53:33 +00:00
parent b18004c13c
commit 1ce0eaa25f
3 changed files with 45 additions and 3 deletions
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25
lib/Analysis/ValueTracking.cpp
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@ -950,8 +950,10 @@ bool llvm::CannotBeNegativeZero(const Value *V, unsigned Depth) {
/// GetLinearExpression - Analyze the specified value as a linear expression:
/// "A*V + B". Return the scale and offset values as APInts and return V as a
/// Value*. The incoming Value is known to be a scalar integer.
/// "A*V + B", where A and B are constant integers. Return the scale and offset
/// values as APInts and return V as a Value*. The incoming Value is known to
/// 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) {
assert(isa<IntegerType>(V->getType()) && "Not an integer value");
@ -984,6 +986,20 @@ static Value *GetLinearExpression(Value *V, APInt &Scale, APInt &Offset,
}
}
// Since clients don't care about the high bits of the value, just scales and
// offsets, we can look through extensions.
if (isa<SExtInst>(V) || isa<ZExtInst>(V)) {
Value *CastOp = cast<CastInst>(V)->getOperand(0);
unsigned OldWidth = Scale.getBitWidth();
unsigned SmallWidth = CastOp->getType()->getPrimitiveSizeInBits();
Scale.trunc(SmallWidth);
Offset.trunc(SmallWidth);
Value *Result = GetLinearExpression(CastOp, Scale, Offset, TD);
Scale.zext(OldWidth);
Offset.zext(OldWidth);
return Result;
}
Scale = 1;
Offset = 0;
return V;
@ -993,6 +1009,11 @@ static Value *GetLinearExpression(Value *V, APInt &Scale, APInt &Offset,
/// into a base pointer with a constant offset and a number of scaled symbolic
/// offsets.
///
/// The scaled symbolic offsets (represented by pairs of a Value* and a scale in
/// the VarIndices vector) are Value*'s that are known to be scaled by the
/// specified amount, but which may have other unrepresented high bits. As such,
/// the gep cannot necessarily be reconstructed from its decomposed form.
///
/// When TargetData is around, this function is capable of analyzing everything
/// that Value::getUnderlyingObject() can look through. When not, it just looks
/// through pointer casts.