From 49623fa77a35de343e89ea2d8159ce719473ce71 Mon Sep 17 00:00:00 2001 From: Simon Pilgrim Date: Fri, 13 Nov 2020 10:47:56 +0000 Subject: [PATCH] [ValueTracking] computeKnownBitsFromShiftOperator use KnownBits direct for constant shift amounts. Let KnownBits shift handlers deal with out-of-range shift amounts. --- llvm/lib/Analysis/ValueTracking.cpp | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp index b369f2697e5c..0a18718fd9b5 100644 --- a/llvm/lib/Analysis/ValueTracking.cpp +++ b/llvm/lib/Analysis/ValueTracking.cpp @@ -993,8 +993,7 @@ static void computeKnownBitsFromShiftOperator( computeKnownBits(I->getOperand(1), DemandedElts, Known, Depth + 1, Q); if (Known.isConstant()) { - unsigned ShiftAmt = Known.getConstant().getLimitedValue(BitWidth - 1); - Known = KF(Known2, KnownBits::makeConstant(APInt(32, ShiftAmt))); + Known = KF(Known2, Known); // If the known bits conflict, this must be an overflowing left shift, so // the shift result is poison. We can return anything we want. Choose 0 for