diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp --- a/llvm/lib/Analysis/InstructionSimplify.cpp +++ b/llvm/lib/Analysis/InstructionSimplify.cpp @@ -3126,6 +3126,17 @@ return getTrue(ITy); } + // (sub C, X) == X, C is odd --> false + // (sub C, X) != X, C is odd --> true + if (match(LBO, m_Sub(m_APInt(C), m_Specific(RHS)))) { + if ((*C & 1) == 1) { + if (Pred == CmpInst::ICMP_EQ) + return ConstantInt::getFalse(getCompareTy(RHS)); + if (Pred == CmpInst::ICMP_NE) + return ConstantInt::getTrue(getCompareTy(RHS)); + } + } + return nullptr; } diff --git a/llvm/test/Transforms/InstSimplify/icmp.ll b/llvm/test/Transforms/InstSimplify/icmp.ll --- a/llvm/test/Transforms/InstSimplify/icmp.ll +++ b/llvm/test/Transforms/InstSimplify/icmp.ll @@ -214,9 +214,7 @@ define i1 @sub_false(i32 %x) { ; CHECK-LABEL: @sub_false( -; CHECK-NEXT: [[SUB:%.*]] = sub i32 1, [[X:%.*]] -; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[SUB]], [[X]] -; CHECK-NEXT: ret i1 [[CMP]] +; CHECK-NEXT: ret i1 false ; %sub = sub i32 1, %x %cmp = icmp eq i32 %sub, %x @@ -225,9 +223,7 @@ define i1 @sub_swap(i8 %x) { ; CHECK-LABEL: @sub_swap( -; CHECK-NEXT: [[SUB:%.*]] = sub i8 3, [[X:%.*]] -; CHECK-NEXT: [[CMP:%.*]] = icmp ne i8 [[X]], [[SUB]] -; CHECK-NEXT: ret i1 [[CMP]] +; CHECK-NEXT: ret i1 true ; %sub = sub i8 3, %x %cmp = icmp ne i8 %x, %sub @@ -236,9 +232,7 @@ define <2 x i1> @sub_odd(<2 x i8> %x) { ; CHECK-LABEL: @sub_odd( -; CHECK-NEXT: [[SUB:%.*]] = sub <2 x i8> , [[X:%.*]] -; CHECK-NEXT: [[CMP:%.*]] = icmp ne <2 x i8> [[SUB]], [[X]] -; CHECK-NEXT: ret <2 x i1> [[CMP]] +; CHECK-NEXT: ret <2 x i1> ; %sub = sub <2 x i8> , %x %cmp = icmp ne <2 x i8> %sub, %x