diff options
Diffstat (limited to 'lib/Transforms')
| -rw-r--r-- | lib/Transforms/Scalar/InstructionCombining.cpp | 22 |
1 files changed, 10 insertions, 12 deletions
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp index 2c73e7ae0f..2a82e0f233 100644 --- a/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/lib/Transforms/Scalar/InstructionCombining.cpp @@ -7299,19 +7299,17 @@ Instruction *InstCombiner::visitICmpInstWithCastAndCast(ICmpInst &ICI) { // If the re-extended constant didn't change... if (Res2 == CI) { - // Make sure that sign of the Cmp and the sign of the Cast are the same. - // For example, we might have: - // %A = sext i16 %X to i32 - // %B = icmp ugt i32 %A, 1330 - // It is incorrect to transform this into - // %B = icmp ugt i16 %X, 1330 - // because %A may have negative value. - // - // However, we allow this when the compare is EQ/NE, because they are - // signless. - if (isSignedExt == isSignedCmp || ICI.isEquality()) + // Deal with equality cases early. + if (ICI.isEquality()) return new ICmpInst(ICI.getPredicate(), LHSCIOp, Res1); - return 0; + + // A signed comparison of sign extended values simplifies into a + // signed comparison. + if (isSignedExt && isSignedCmp) + return new ICmpInst(ICI.getPredicate(), LHSCIOp, Res1); + + // The other three cases all fold into an unsigned comparison. + return new ICmpInst(ICI.getUnsignedPredicate(), LHSCIOp, Res1); } // The re-extended constant changed so the constant cannot be represented |