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Always compute all the bits in ComputeMaskedBits.

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This allows us to keep passing reduced masks to SimplifyDemandedBits, but
know about all the bits if SimplifyDemandedBits fails. This allows instcombine
to simplify cases like the one in the included testcase.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154011 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Rafael Espindola
2012-04-04 12:51:34 +00:00
parent 00b73a5e44
commit 26c8dcc692
35 changed files with 265 additions and 417 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lib/Analysis/ScalarEvolution.cpp
+3 -6
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@@ -3261,9 +3261,8 @@ ScalarEvolution::GetMinTrailingZeros(const SCEV *S) {
if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
// For a SCEVUnknown, ask ValueTracking.
unsigned BitWidth = getTypeSizeInBits(U->getType());
APInt Mask = APInt::getAllOnesValue(BitWidth);
APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
ComputeMaskedBits(U->getValue(), Mask, Zeros, Ones);
ComputeMaskedBits(U->getValue(), Zeros, Ones);
return Zeros.countTrailingOnes();
}
@@ -3401,9 +3400,8 @@ ScalarEvolution::getUnsignedRange(const SCEV *S) {
if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
// For a SCEVUnknown, ask ValueTracking.
APInt Mask = APInt::getAllOnesValue(BitWidth);
APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
ComputeMaskedBits(U->getValue(), Mask, Zeros, Ones, TD);
ComputeMaskedBits(U->getValue(), Zeros, Ones, TD);
if (Ones == ~Zeros + 1)
return setUnsignedRange(U, ConservativeResult);
return setUnsignedRange(U,
@@ -3660,9 +3658,8 @@ const SCEV *ScalarEvolution::createSCEV(Value *V) {
// knew about to reconstruct a low-bits mask value.
unsigned LZ = A.countLeadingZeros();
unsigned BitWidth = A.getBitWidth();
APInt AllOnes = APInt::getAllOnesValue(BitWidth);
APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
ComputeMaskedBits(U->getOperand(0), AllOnes, KnownZero, KnownOne, TD);
ComputeMaskedBits(U->getOperand(0), KnownZero, KnownOne, TD);
APInt EffectiveMask = APInt::getLowBitsSet(BitWidth, BitWidth - LZ);