From 2c47368a7d843486a59e12a08595297003e3cb2d Mon Sep 17 00:00:00 2001 From: Duncan Sands Date: Thu, 28 Jan 2010 17:22:42 +0000 Subject: [PATCH] Fix PR6165. The bug was that LHSKnownZero was being and'd with DemandedMask when it should have been and'd with LowBits. Fix that and while there beef up the logic in the case of a negative LHS. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@94745 91177308-0d34-0410-b5e6-96231b3b80d8 --- .../InstCombine/InstCombineSimplifyDemanded.cpp | 13 +++++++++++-- .../Transforms/InstCombine/2010-01-28-NegativeSRem.ll | 19 +++++++++++++++++++ 2 files changed, 30 insertions(+), 2 deletions(-) create mode 100644 test/Transforms/InstCombine/2010-01-28-NegativeSRem.ll diff --git a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp index 74a1b6803d4..ec1ed664961 100644 --- a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp +++ b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp @@ -681,10 +681,19 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, LHSKnownZero, LHSKnownOne, Depth+1)) return I; + // The low bits of LHS are unchanged by the srem. + KnownZero |= LHSKnownZero & LowBits; + KnownOne |= LHSKnownOne & LowBits; + + // If LHS is non-negative or has all low bits zero, then the upper bits + // are all zero. if (LHSKnownZero[BitWidth-1] || ((LHSKnownZero & LowBits) == LowBits)) - LHSKnownZero |= ~LowBits; + KnownZero |= ~LowBits; - KnownZero |= LHSKnownZero & DemandedMask; + // If LHS is negative and not all low bits are zero, then the upper bits + // are all one. + if (LHSKnownOne[BitWidth-1] && ((LHSKnownOne & LowBits) != 0)) + KnownOne |= ~LowBits; assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?"); } diff --git a/test/Transforms/InstCombine/2010-01-28-NegativeSRem.ll b/test/Transforms/InstCombine/2010-01-28-NegativeSRem.ll new file mode 100644 index 00000000000..4ab9bf0c3f5 --- /dev/null +++ b/test/Transforms/InstCombine/2010-01-28-NegativeSRem.ll @@ -0,0 +1,19 @@ +; RUN: opt < %s -instcombine -S | FileCheck %s +; PR6165 + +define i32 @f() { +entry: + br label %BB1 + +BB1: ; preds = %BB1, %entry +; CHECK: BB1: + %x = phi i32 [ -29, %entry ], [ 0, %BB1 ] ; [#uses=2] + %rem = srem i32 %x, 2 ; [#uses=1] + %t = icmp eq i32 %rem, -1 ; [#uses=1] + br i1 %t, label %BB2, label %BB1 +; CHECK-NOT: br i1 false + +BB2: ; preds = %BB1 +; CHECK: BB2: + ret i32 %x +} -- 2.11.0