diff options
| -rw-r--r-- | lib/VMCore/ConstantFold.cpp | 9 | ||||
| -rw-r--r-- | test/Transforms/InstCombine/icmp.ll | 23 |
2 files changed, 31 insertions, 1 deletions
diff --git a/lib/VMCore/ConstantFold.cpp b/lib/VMCore/ConstantFold.cpp index ec62502..3567266 100644 --- a/lib/VMCore/ConstantFold.cpp +++ b/lib/VMCore/ConstantFold.cpp @@ -1817,8 +1817,15 @@ Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred, return Constant::getAllOnesValue(ResultTy); // Handle some degenerate cases first - if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) + if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { + // For EQ and NE, we can always pick a value for the undef to make the + // predicate pass or fail, so we can return undef. + if (ICmpInst::isEquality(ICmpInst::Predicate(pred))) + return UndefValue::get(ResultTy); + // Otherwise, pick the same value as the non-undef operand, and fold + // it to true or false. return ConstantInt::get(ResultTy, CmpInst::isTrueWhenEqual(pred)); + } // No compile-time operations on this type yet. if (C1->getType()->isPPC_FP128Ty()) diff --git a/test/Transforms/InstCombine/icmp.ll b/test/Transforms/InstCombine/icmp.ll index 29997bf..802957f 100644 --- a/test/Transforms/InstCombine/icmp.ll +++ b/test/Transforms/InstCombine/icmp.ll @@ -131,3 +131,26 @@ entry: ; CHECK: ret i1 false } +define i1 @test14(i8 %X) nounwind readnone { +entry: + %cmp = icmp slt i8 undef, -128 + ret i1 %cmp +; CHECK: @test14 +; CHECK: ret i1 false +} + +define i1 @test15() nounwind readnone { +entry: + %cmp = icmp eq i8 undef, -128 + ret i1 %cmp +; CHECK: @test15 +; CHECK: ret i1 undef +} + +define i1 @test16() nounwind readnone { +entry: + %cmp = icmp ne i8 undef, -128 + ret i1 %cmp +; CHECK: @test16 +; CHECK: ret i1 undef +} |