diff options
Diffstat (limited to 'llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp')
| -rw-r--r-- | llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp index 1e5e0724f08..4fa438a2795 100644 --- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp @@ -2834,6 +2834,12 @@ KnownBits SelectionDAG::computeKnownBits(SDValue Op, const APInt &DemandedElts, Known.One <<= Shift; // Low bits are known zero. Known.Zero.setLowBits(Shift); + } else { + // No matter the shift amount, the trailing zeros will stay zero. + Known = computeKnownBits(Op.getOperand(0), DemandedElts, Depth + 1); + Known.Zero = + APInt::getLowBitsSet(BitWidth, Known.countMinTrailingZeros()); + Known.One.clearAllBits(); } break; case ISD::SRL: @@ -2847,6 +2853,11 @@ KnownBits SelectionDAG::computeKnownBits(SDValue Op, const APInt &DemandedElts, } else if (const APInt *ShMinAmt = getValidMinimumShiftAmountConstant(Op)) { // Minimum shift high bits are known zero. Known.Zero.setHighBits(ShMinAmt->getZExtValue()); + } else { + // No matter the shift amount, the leading zeros will stay zero. + Known = computeKnownBits(Op.getOperand(0), DemandedElts, Depth + 1); + Known.Zero = APInt::getHighBitsSet(BitWidth, Known.countMinLeadingZeros()); + Known.One.clearAllBits(); } break; case ISD::SRA: |
