[DAGCombine] (add X, (addcarry Y, 0, Carry)) -> (addcarry X, Y, Carry)

[deadalnix]

Summary

Common pattern when legalizing large integers operations. Similar to D32687, when the carry isn't used.

[RKSimon]

LGTM

lib/CodeGen/SelectionDAG/DAGCombiner.cpp

if (N1.getOpcode() == ISD::SIGN_EXTEND_INREG) {
     VTSDNode *TN = cast<VTSDNode>(N1.getOperand(1));
     if (TN->getVT() == MVT::i1) {
       SDValue ZExt = DAG.getNode(ISD::AND, DL, VT, N1.getOperand(0),
                                  DAG.getConstant(1, DL, VT));
       return DAG.getNode(ISD::SUB, DL, VT, N0, ZExt);
     }
   }
 
+  // (add X, (addcarry Y, 0, Carry)) -> (addcarry X, Y, Carry)
+  if (N1.getOpcode() == ISD::ADDCARRY && isNullConstant(N1.getOperand(1)))
+    return DAG.getNode(ISD::ADDCARRY, DL, N1->getVTList(),
+                       N0, N1.getOperand(0), N1.getOperand(2));
+
   return SDValue();
 }
 
 SDValue DAGCombiner::visitADDC(SDNode *N) {
   SDValue N0 = N->getOperand(0);
   SDValue N1 = N->getOperand(1);
   EVT VT = N0.getValueType();
   SDLoc DL(N);

test/CodeGen/X86/adde-carry.ll

  store i32 %6, i32* %r, align 4
  ret void
 }
 
 define void @c(i16* nocapture %r, i64 %a, i64 %b, i16 %c) nounwind {
 ; CHECK-LABEL: c:
 ; CHECK:       # BB#0: # %entry
 ; CHECK-NEXT:    addq %rdx, %rsi
-; CHECK-NEXT:    adcl $0, %ecx
+; CHECK-NEXT:    adcw $0, %cx
 ; CHECK-NEXT:    movw %cx, (%rdi)
 ; CHECK-NEXT:    retq
 entry:
  %0 = zext i64 %a to i128
  %1 = zext i64 %b to i128
  %2 = zext i16 %c to i128
  %3 = add i128 %1, %0
  %4 = lshr i128 %3, 64
  %5 = add i128 %4, %2
  %6 = trunc i128 %5 to i16
  store i16 %6, i16* %r, align 4
  ret void
 }
 
 define void @d(i8* nocapture %r, i64 %a, i64 %b, i8 %c) nounwind {
 ; CHECK-LABEL: d:
 ; CHECK:       # BB#0: # %entry
 ; CHECK-NEXT:    addq %rdx, %rsi
-; CHECK-NEXT:    adcl $0, %ecx
+; CHECK-NEXT:    adcb $0, %cl
 ; CHECK-NEXT:    movb %cl, (%rdi)
 ; CHECK-NEXT:    retq
 entry:
  %0 = zext i64 %a to i128
  %1 = zext i64 %b to i128
  %2 = zext i8 %c to i128
  %3 = add i128 %1, %0
  %4 = lshr i128 %3, 64
  %5 = add i128 %4, %2
  %6 = trunc i128 %5 to i8
  store i8 %6, i8* %r, align 4
  ret void
 }
 
 %scalar = type { [4 x i64] }
 
 define %scalar @pr31719(%scalar* nocapture readonly %this, %scalar %arg.b) {
 ; CHECK-LABEL: pr31719:
 ; CHECK:       # BB#0: # %entry
 ; CHECK-NEXT:    addq (%rsi), %rdx
 ; CHECK-NEXT:    sbbq %r10, %r10
 ; CHECK-NEXT:    andl $1, %r10d
 ; CHECK-NEXT:    addq 8(%rsi), %rcx
-; CHECK-NEXT:    sbbq %r11, %r11
-; CHECK-NEXT:    andl $1, %r11d
-; CHECK-NEXT:    addq %r10, %rcx
-; CHECK-NEXT:    adcq $0, %r11
-; CHECK-NEXT:    addq 16(%rsi), %r8
 ; CHECK-NEXT:    sbbq %rax, %rax
 ; CHECK-NEXT:    andl $1, %eax
-; CHECK-NEXT:    addq %r11, %r8
+; CHECK-NEXT:    addq %r10, %rcx
 ; CHECK-NEXT:    adcq $0, %rax
+; CHECK-NEXT:    addq 16(%rsi), %r8
+; CHECK-NEXT:    sbbq %r10, %r10
+; CHECK-NEXT:    andl $1, %r10d
 ; CHECK-NEXT:    addq 24(%rsi), %r9
-; CHECK-NEXT:    addq %rax, %r9
+; CHECK-NEXT:    addq %rax, %r8
+; CHECK-NEXT:    adcq %r10, %r9
 ; CHECK-NEXT:    movq %rdx, (%rdi)
 ; CHECK-NEXT:    movq %rcx, 8(%rdi)
 ; CHECK-NEXT:    movq %r8, 16(%rdi)
 ; CHECK-NEXT:    movq %r9, 24(%rdi)
 ; CHECK-NEXT:    movq %rdi, %rax
 ; CHECK-NEXT:    retq
 entry:
   %0 = extractvalue %scalar %arg.b, 0

 ; CHECK:       # BB#0: # %entry
 ; CHECK-NEXT:    movq %rdx, %rax
 ; CHECK-NEXT:    mulq %rsi
 ; CHECK-NEXT:    addq (%rdi), %rax
 ; CHECK-NEXT:    adcq $0, %rdx
 ; CHECK-NEXT:    movq %rax, (%rdi)
 ; CHECK-NEXT:    addq 8(%rdi), %rdx
 ; CHECK-NEXT:    movq %rdx, 8(%rdi)
-; CHECK-NEXT:    sbbl %eax, %eax
-; CHECK-NEXT:    subl %eax, 16(%rdi)
+; CHECK-NEXT:    adcl $0, 16(%rdi)
 ; CHECK-NEXT:    retq
 entry:
   %0 = zext i64 %arg.a to i128
   %1 = zext i64 %arg.b to i128
   %2 = mul nuw i128 %1, %0
   %3 = getelementptr inbounds %accumulator, %accumulator* %this, i64 0, i32 0
   %4 = load i64, i64* %3, align 8
   %5 = zext i64 %4 to i128