diff options
| author | Duncan Sands <baldrick@free.fr> | 2012-04-30 11:56:58 +0000 |
|---|---|---|
| committer | Duncan Sands <baldrick@free.fr> | 2012-04-30 11:56:58 +0000 |
| commit | 5ff30e70f8dc4ddfdb3bd6925ccdf524130a7b95 (patch) | |
| tree | f063cefea11403837e9ffc79cad33e8d7cbf9d14 | |
| parent | bfbab99b58aa530d5d6aa886ef66be42a047c756 (diff) | |
Just mark the sign bit as known zero, rather than any other irrelevant bits
known zero in the LHS. Fixes PR12541.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155818 91177308-0d34-0410-b5e6-96231b3b80d8
| -rw-r--r-- | lib/Analysis/ValueTracking.cpp | 2 | ||||
| -rw-r--r-- | test/Transforms/InstCombine/2012-04-30-SRem.ll | 12 |
2 files changed, 13 insertions, 1 deletions
diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp index a430f6281e..1418e01d7c 100644 --- a/lib/Analysis/ValueTracking.cpp +++ b/lib/Analysis/ValueTracking.cpp @@ -564,7 +564,7 @@ void llvm::ComputeMaskedBits(Value *V, APInt &KnownZero, APInt &KnownOne, Depth+1); // If it's known zero, our sign bit is also zero. if (LHSKnownZero.isNegative()) - KnownZero |= LHSKnownZero; + KnownZero.setBit(BitWidth - 1); } break; diff --git a/test/Transforms/InstCombine/2012-04-30-SRem.ll b/test/Transforms/InstCombine/2012-04-30-SRem.ll new file mode 100644 index 0000000000..a285d5aea5 --- /dev/null +++ b/test/Transforms/InstCombine/2012-04-30-SRem.ll @@ -0,0 +1,12 @@ +; RUN: opt -instcombine -S < %s | FileCheck %s +; PR12541 + +define i32 @foo(i32 %x) { + %y = xor i32 %x, 3 + %z = srem i32 1656690544, %y + %sext = shl i32 %z, 24 + %s = ashr exact i32 %sext, 24 + ret i32 %s +; CHECK-NOT: and +; The shifts were wrongly being turned into an and with 112 +} |