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Add computeMaskedBitsLoad back, as it was the change to instsimplify that

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caused the slowdown last time.

llvm-svn: 153747
This commit is contained in:
Rafael Espindola 2012-03-30 15:52:11 +00:00
parent 0365dc97a8
commit 4578d5e45a
1 changed files with 26 additions and 0 deletions
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26
lib/Analysis/ValueTracking.cpp
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@ -20,8 +20,10 @@
#include "llvm/GlobalAlias.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/LLVMContext.h"
#include "llvm/Metadata.h"
#include "llvm/Operator.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Support/ConstantRange.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/PatternMatch.h"
@ -195,6 +197,26 @@ static void ComputeMaskedBitsMul(Value *Op0, Value *Op1, bool NSW,
KnownOne.setBit(BitWidth - 1);
}
static void computeMaskedBitsLoad(const MDNode &Ranges, const APInt &Mask,
APInt &KnownZero) {
unsigned BitWidth = Mask.getBitWidth();
unsigned NumRanges = Ranges.getNumOperands() / 2;
assert(NumRanges >= 1);
// Use the high end of the ranges to find leading zeros.
unsigned MinLeadingZeros = BitWidth;
for (unsigned i = 0; i < NumRanges; ++i) {
ConstantInt *Lower = cast<ConstantInt>(Ranges.getOperand(2*i + 0));
ConstantInt *Upper = cast<ConstantInt>(Ranges.getOperand(2*i + 1));
ConstantRange Range(Lower->getValue(), Upper->getValue());
if (Range.isWrappedSet())
MinLeadingZeros = 0; // -1 has no zeros
unsigned LeadingZeros = (Upper->getValue() - 1).countLeadingZeros();
MinLeadingZeros = std::min(LeadingZeros, MinLeadingZeros);
}
KnownZero = Mask & APInt::getHighBitsSet(BitWidth, MinLeadingZeros);
}
/// ComputeMaskedBits - Determine which of the bits specified in Mask are
/// known to be either zero or one and return them in the KnownZero/KnownOne
/// bit sets. This code only analyzes bits in Mask, in order to short-circuit
@ -315,6 +337,10 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask,
APInt KnownZero2(KnownZero), KnownOne2(KnownOne);
switch (I->getOpcode()) {
default: break;
case Instruction::Load:
if (MDNode *MD = cast<LoadInst>(I)->getMetadata(LLVMContext::MD_range))
computeMaskedBitsLoad(*MD, Mask, KnownZero);
return;
case Instruction::And: {
// If either the LHS or the RHS are Zero, the result is zero.
ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, TD, Depth+1);