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| author | Benjamin Kramer <benny.kra@googlemail.com> | 2013-05-09 16:32:32 +0000 |
|---|---|---|
| committer | Benjamin Kramer <benny.kra@googlemail.com> | 2013-05-09 16:32:32 +0000 |
| commit | a6ff92a975f2d6ef6a0db7aeaee3ee9fd046307a (patch) | |
| tree | 26ad2cbb1ac595d2837ddec0bbfd14ef507b1dca | |
| parent | 4fcf82f3163f34ddc5c659ceb20e87057a287e10 (diff) | |
| download | llvm-a6ff92a975f2d6ef6a0db7aeaee3ee9fd046307a.tar.gz llvm-a6ff92a975f2d6ef6a0db7aeaee3ee9fd046307a.tar.bz2 llvm-a6ff92a975f2d6ef6a0db7aeaee3ee9fd046307a.tar.xz | |
InstCombine: Don't just copy known bits from the first operand of an srem.
That's obviously wrong. Conservatively restrict it to the sign bit, which
matches the original intention of this analysis. Fixes PR15940.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181518 91177308-0d34-0410-b5e6-96231b3b80d8
| -rw-r--r-- | lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp | 2 | ||||
| -rw-r--r-- | test/Transforms/InstCombine/icmp.ll | 12 |
2 files changed, 13 insertions, 1 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp index 8add1ea618..a7bfe0965b 100644 --- a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp +++ b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp @@ -754,7 +754,7 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, ComputeMaskedBits(I->getOperand(0), LHSKnownZero, LHSKnownOne, Depth+1); // If it's known zero, our sign bit is also zero. if (LHSKnownZero.isNegative()) - KnownZero |= LHSKnownZero; + KnownZero.setBit(KnownZero.getBitWidth() - 1); } break; case Instruction::URem: { diff --git a/test/Transforms/InstCombine/icmp.ll b/test/Transforms/InstCombine/icmp.ll index c912a576c3..ed1cd1e5a4 100644 --- a/test/Transforms/InstCombine/icmp.ll +++ b/test/Transforms/InstCombine/icmp.ll @@ -707,6 +707,18 @@ define i1 @test69(i32 %c) nounwind uwtable { ret i1 %3 } +; PR15940 +; CHECK: @test70 +; CHECK-NEXT: %A = srem i32 5, %X +; CHECK-NEXT: %C = icmp ne i32 %A, 2 +; CHECK-NEXT: ret i1 %C +define i1 @test70(i32 %X) { + %A = srem i32 5, %X + %B = add i32 %A, 2 + %C = icmp ne i32 %B, 4 + ret i1 %C +} + ; CHECK: @icmp_sext16trunc ; CHECK-NEXT: %1 = trunc i32 %x to i16 ; CHECK-NEXT: %cmp = icmp slt i16 %1, 36 |