From ef5debac4302cd479ddd9e784a5b5acc8c2b9804 Mon Sep 17 00:00:00 2001 From: Simon Pilgrim Date: Mon, 13 Jan 2020 12:01:56 +0000 Subject: [SelectionDAG] ComputeKnownBits add getValidMinimumShiftAmountConstant() ISD::SHL support As mentioned on D72573 --- llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp | 3 +++ 1 file changed, 3 insertions(+) (limited to 'llvm/lib/CodeGen') diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp index 4fa438a2795..59180597130 100644 --- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp @@ -2834,6 +2834,9 @@ KnownBits SelectionDAG::computeKnownBits(SDValue Op, const APInt &DemandedElts, Known.One <<= Shift; // Low bits are known zero. Known.Zero.setLowBits(Shift); + } else if (const APInt *ShMinAmt = getValidMinimumShiftAmountConstant(Op)) { + // Minimum shift low bits are known zero. + Known.Zero.setLowBits(ShMinAmt->getZExtValue()); } else { // No matter the shift amount, the trailing zeros will stay zero. Known = computeKnownBits(Op.getOperand(0), DemandedElts, Depth + 1); -- cgit v1.2.3