Index: llvm/trunk/lib/Transforms/Scalar/EarlyCSE.cpp =================================================================== --- llvm/trunk/lib/Transforms/Scalar/EarlyCSE.cpp +++ llvm/trunk/lib/Transforms/Scalar/EarlyCSE.cpp @@ -174,12 +174,17 @@ } if (CmpInst *CI = dyn_cast(Inst)) { + // Compares can be commuted by swapping the comparands and + // updating the predicate. Choose the form that has the + // comparands in sorted order, or in the case of a tie, the + // one with the lower predicate. Value *LHS = CI->getOperand(0); Value *RHS = CI->getOperand(1); CmpInst::Predicate Pred = CI->getPredicate(); - if (Inst->getOperand(0) > Inst->getOperand(1)) { + CmpInst::Predicate SwappedPred = CI->getSwappedPredicate(); + if (std::tie(LHS, Pred) > std::tie(RHS, SwappedPred)) { std::swap(LHS, RHS); - Pred = CI->getSwappedPredicate(); + Pred = SwappedPred; } return hash_combine(Inst->getOpcode(), Pred, LHS, RHS); } Index: llvm/trunk/test/Transforms/EarlyCSE/commute.ll =================================================================== --- llvm/trunk/test/Transforms/EarlyCSE/commute.ll +++ llvm/trunk/test/Transforms/EarlyCSE/commute.ll @@ -72,6 +72,22 @@ ret void } +; Test degenerate case of commuted compare of identical comparands. + +define void @test6(float %f, i1* %p1, i1* %p2) { +; CHECK-LABEL: @test6( +; CHECK-NEXT: [[C1:%.*]] = fcmp ult float [[F:%.*]], [[F]] +; CHECK-NEXT: store i1 [[C1]], i1* [[P1:%.*]] +; CHECK-NEXT: store i1 [[C1]], i1* [[P2:%.*]] +; CHECK-NEXT: ret void +; + %c1 = fcmp ult float %f, %f + %c2 = fcmp ugt float %f, %f + store i1 %c1, i1* %p1 + store i1 %c2, i1* %p2 + ret void +} + ; Min/max operands may be commuted in the compare and select. define i8 @smin_commute(i8 %a, i8 %b) {