diff options
Diffstat (limited to 'lib/Analysis/ValueTracking.cpp')
| -rw-r--r-- | lib/Analysis/ValueTracking.cpp | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp index 19fde0e419..491224a4b6 100644 --- a/lib/Analysis/ValueTracking.cpp +++ b/lib/Analysis/ValueTracking.cpp @@ -470,7 +470,7 @@ void llvm::ComputeMaskedBits(Value *V, APInt &KnownZero, APInt &KnownOne, return; } case Instruction::Shl: - // (shl X, C1) & C2 == 0 if (X & C2 >>u C1) == 0 + // (shl X, C1) & C2 == 0 iff (X & C2 >>u C1) == 0 if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) { uint64_t ShiftAmt = SA->getLimitedValue(BitWidth); ComputeMaskedBits(I->getOperand(0), KnownZero, KnownOne, TD, Depth+1); @@ -482,7 +482,7 @@ void llvm::ComputeMaskedBits(Value *V, APInt &KnownZero, APInt &KnownOne, } break; case Instruction::LShr: - // (ushr X, C1) & C2 == 0 if (-1 >> C1) & C2 == 0 + // (ushr X, C1) & C2 == 0 iff (-1 >> C1) & C2 == 0 if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) { // Compute the new bits that are at the top now. uint64_t ShiftAmt = SA->getLimitedValue(BitWidth); @@ -498,7 +498,7 @@ void llvm::ComputeMaskedBits(Value *V, APInt &KnownZero, APInt &KnownOne, } break; case Instruction::AShr: - // (ashr X, C1) & C2 == 0 if (-1 >> C1) & C2 == 0 + // (ashr X, C1) & C2 == 0 iff (-1 >> C1) & C2 == 0 if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) { // Compute the new bits that are at the top now. uint64_t ShiftAmt = SA->getLimitedValue(BitWidth-1); |