diff options
Diffstat (limited to 'llvm')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp | 5 | ||||
| -rw-r--r-- | llvm/test/Transforms/InstCombine/icmp-sub.ll | 40 |
2 files changed, 45 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp index 5e0a3c37979..952f295cce4 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -2411,6 +2411,11 @@ Instruction *InstCombiner::foldICmpSubConstant(ICmpInst &Cmp, const APInt *C2; APInt SubResult; + // icmp eq/ne (sub C, Y), C -> icmp eq/ne Y, 0 + if (match(X, m_APInt(C2)) && *C2 == C && Cmp.isEquality()) + return new ICmpInst(Cmp.getPredicate(), Y, + ConstantInt::get(Y->getType(), 0)); + // (icmp P (sub nuw|nsw C2, Y), C) -> (icmp swap(P) Y, C2-C) if (match(X, m_APInt(C2)) && ((Cmp.isUnsigned() && Sub->hasNoUnsignedWrap()) || diff --git a/llvm/test/Transforms/InstCombine/icmp-sub.ll b/llvm/test/Transforms/InstCombine/icmp-sub.ll index c66581b3b5a..3e7cb4edc1d 100644 --- a/llvm/test/Transforms/InstCombine/icmp-sub.ll +++ b/llvm/test/Transforms/InstCombine/icmp-sub.ll @@ -84,3 +84,43 @@ define i1 @test_negative_combined_sub_signed_overflow(i8 %x) { %z = icmp slt i8 %y, -1 ret i1 %z } + +define i1 @test_sub_0_Y_eq_0(i8 %y) { +; CHECK-LABEL: @test_sub_0_Y_eq_0( +; CHECK-NEXT: [[Z:%.*]] = icmp eq i8 [[Y:%.*]], 0 +; CHECK-NEXT: ret i1 [[Z]] +; + %s = sub i8 0, %y + %z = icmp eq i8 %s, 0 + ret i1 %z +} + +define i1 @test_sub_0_Y_ne_0(i8 %y) { +; CHECK-LABEL: @test_sub_0_Y_ne_0( +; CHECK-NEXT: [[Z:%.*]] = icmp ne i8 [[Y:%.*]], 0 +; CHECK-NEXT: ret i1 [[Z]] +; + %s = sub i8 0, %y + %z = icmp ne i8 %s, 0 + ret i1 %z +} + +define i1 @test_sub_4_Y_ne_4(i8 %y) { +; CHECK-LABEL: @test_sub_4_Y_ne_4( +; CHECK-NEXT: [[Z:%.*]] = icmp ne i8 [[Y:%.*]], 0 +; CHECK-NEXT: ret i1 [[Z]] +; + %s = sub i8 4, %y + %z = icmp ne i8 %s, 4 + ret i1 %z +} + +define i1 @test_sub_127_Y_eq_127(i8 %y) { +; CHECK-LABEL: @test_sub_127_Y_eq_127( +; CHECK-NEXT: [[Z:%.*]] = icmp eq i8 [[Y:%.*]], 0 +; CHECK-NEXT: ret i1 [[Z]] +; + %s = sub i8 127, %y + %z = icmp eq i8 %s, 127 + ret i1 %z +} |
