Index: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp =================================================================== --- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -2217,7 +2217,8 @@ SDNode *N) { // Iff the flag result is dead: // (addcarry (add|uaddo X, Y), 0, Carry) -> (addcarry X, Y, Carry) - if ((N0.getOpcode() == ISD::ADD || N0.getOpcode() == ISD::UADDO) && + if ((N0.getOpcode() == ISD::ADD || + (N0.getOpcode() == ISD::UADDO && N0.getResNo() == 0)) && isNullConstant(N1) && !N->hasAnyUseOfValue(1)) return DAG.getNode(ISD::ADDCARRY, SDLoc(N), N->getVTList(), N0.getOperand(0), N0.getOperand(1), CarryIn); Index: llvm/trunk/test/CodeGen/X86/addcarry.ll =================================================================== --- llvm/trunk/test/CodeGen/X86/addcarry.ll +++ llvm/trunk/test/CodeGen/X86/addcarry.ll @@ -81,6 +81,30 @@ ret void } +define i8 @e(i32* nocapture %a, i32 %b) nounwind { +; CHECK-LABEL: e: +; CHECK: # BB#0: +; CHECK-NEXT: # kill: %ESI %ESI %RSI +; CHECK-NEXT: movl (%rdi), %ecx +; CHECK-NEXT: leal (%rsi,%rcx), %edx +; CHECK-NEXT: addl %esi, %edx +; CHECK-NEXT: setb %al +; CHECK-NEXT: addl %esi, %ecx +; CHECK-NEXT: movl %edx, (%rdi) +; CHECK-NEXT: adcb $0, %al +; CHECK-NEXT: retq + %1 = load i32, i32* %a, align 4 + %2 = add i32 %1, %b + %3 = icmp ult i32 %2, %b + %4 = zext i1 %3 to i8 + %5 = add i32 %2, %b + store i32 %5, i32* %a, align 4 + %6 = icmp ult i32 %5, %b + %7 = zext i1 %6 to i8 + %8 = add nuw nsw i8 %7, %4 + ret i8 %8 +} + %scalar = type { [4 x i64] } define %scalar @pr31719(%scalar* nocapture readonly %this, %scalar %arg.b) {