Index: lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -2892,6 +2892,17 @@
   if (SDValue Combined = visitADDCARRYLike(N1, N0, CarryIn, N))
     return Combined;
 
+  // We want to avoid useless duplication.
+  // TODO: This is done automatically for binary operations. As ADDCARRY is
+  // not a binary operation, this is not really possible to leverage this
+  // existing mechanism for it. However, if more operations require the same
+  // deduplication logic, then it may be worth generalize.
+  SDValue Ops[] = {N1, N0, CarryIn};
+  SDNode *CSENode = DAG.getNodeIfExists(ISD::ADDCARRY, N->getVTList(), Ops,
+                                        N->getFlags());
+  if (CSENode)
+    return SDValue(CSENode, 0);
+
   return SDValue();
 }
 
Index: test/CodeGen/X86/addcarry.ll
===================================================================
--- test/CodeGen/X86/addcarry.ll
+++ test/CodeGen/X86/addcarry.ll
@@ -312,31 +312,15 @@
 define %S @readd(%S* nocapture readonly %this, %S %arg.b) {
 ; CHECK-LABEL: readd:
 ; CHECK:       # %bb.0: # %entry
-; CHECK-NEXT:    pushq %rbx
-; CHECK-NEXT:    .cfi_def_cfa_offset 16
-; CHECK-NEXT:    .cfi_offset %rbx, -16
 ; CHECK-NEXT:    movq %rdi, %rax
-; CHECK-NEXT:    movq (%rsi), %r10
-; CHECK-NEXT:    movq %rdx, %rdi
-; CHECK-NEXT:    addq %r10, %rdi
-; CHECK-NEXT:    movq 8(%rsi), %rdi
-; CHECK-NEXT:    movq 16(%rsi), %r11
-; CHECK-NEXT:    movq %rcx, %rbx
-; CHECK-NEXT:    adcq %rdi, %rbx
-; CHECK-NEXT:    addq %r10, %rdx
-; CHECK-NEXT:    adcq %rdi, %rcx
-; CHECK-NEXT:    setb %cl
-; CHECK-NEXT:    movq %r8, %rdi
-; CHECK-NEXT:    adcq %r11, %rdi
-; CHECK-NEXT:    addb $255, %cl
-; CHECK-NEXT:    adcq %r11, %r8
+; CHECK-NEXT:    addq (%rsi), %rdx
+; CHECK-NEXT:    adcq 8(%rsi), %rcx
+; CHECK-NEXT:    adcq 16(%rsi), %r8
 ; CHECK-NEXT:    adcq 24(%rsi), %r9
-; CHECK-NEXT:    movq %rdx, (%rax)
-; CHECK-NEXT:    movq %rbx, 8(%rax)
-; CHECK-NEXT:    movq %rdi, 16(%rax)
-; CHECK-NEXT:    movq %r9, 24(%rax)
-; CHECK-NEXT:    popq %rbx
-; CHECK-NEXT:    .cfi_def_cfa_offset 8
+; 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:    retq
 entry:
   %0 = extractvalue %S %arg.b, 0
@@ -398,16 +382,13 @@
 define i128 @addcarry_to_subcarry(i64 %a, i64 %b) {
 ; CHECK-LABEL: addcarry_to_subcarry:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    notq %rsi
-; CHECK-NEXT:    movb $1, %al
-; CHECK-NEXT:    addb $-1, %al
-; CHECK-NEXT:    movq %rdi, %rax
-; CHECK-NEXT:    adcq %rsi, %rax
-; CHECK-NEXT:    setb %cl
-; CHECK-NEXT:    movq %rdi, %rax
-; CHECK-NEXT:    adcq %rsi, %rax
-; CHECK-NEXT:    addb $255, %cl
-; CHECK-NEXT:    adcq %rdi, %rsi
+; CHECK-NEXT:    movq %rsi, %rax
+; CHECK-NEXT:    notq %rax
+; CHECK-NEXT:    movb $1, %cl
+; CHECK-NEXT:    addb $-1, %cl
+; CHECK-NEXT:    movq %rdi, %rcx
+; CHECK-NEXT:    adcq %rax, %rcx
+; CHECK-NEXT:    adcq %rdi, %rax
 ; CHECK-NEXT:    setb %cl
 ; CHECK-NEXT:    movzbl %cl, %edx
 ; CHECK-NEXT:    retq
Index: test/CodeGen/X86/subcarry.ll
===================================================================
--- test/CodeGen/X86/subcarry.ll
+++ test/CodeGen/X86/subcarry.ll
@@ -90,44 +90,24 @@
 define %S @sub(%S* nocapture readonly %this, %S %arg.b) local_unnamed_addr {
 ; CHECK-LABEL: sub:
 ; CHECK:       # %bb.0: # %entry
-; CHECK-NEXT:    pushq %r14
-; CHECK-NEXT:    .cfi_def_cfa_offset 16
-; CHECK-NEXT:    pushq %rbx
-; CHECK-NEXT:    .cfi_def_cfa_offset 24
-; CHECK-NEXT:    .cfi_offset %rbx, -24
-; CHECK-NEXT:    .cfi_offset %r14, -16
 ; CHECK-NEXT:    movq %rdi, %rax
-; CHECK-NEXT:    movq %rdx, %rdi
-; CHECK-NEXT:    notq %rdi
-; CHECK-NEXT:    movq (%rsi), %r10
-; CHECK-NEXT:    movq 8(%rsi), %r11
-; CHECK-NEXT:    movb $1, %bl
-; CHECK-NEXT:    addb $-1, %bl
-; CHECK-NEXT:    adcq %r10, %rdi
+; CHECK-NEXT:    movq (%rsi), %rdi
+; CHECK-NEXT:    movq %rdi, %r10
+; CHECK-NEXT:    subq %rdx, %r10
+; CHECK-NEXT:    notq %rdx
+; CHECK-NEXT:    movb $1, %r11b
+; CHECK-NEXT:    addb $-1, %r11b
+; CHECK-NEXT:    adcq %rdi, %rdx
 ; CHECK-NEXT:    notq %rcx
-; CHECK-NEXT:    setb %bl
-; CHECK-NEXT:    movq %rcx, %rdi
-; CHECK-NEXT:    adcq %r11, %rdi
-; CHECK-NEXT:    movq 16(%rsi), %r14
-; CHECK-NEXT:    addb $255, %bl
-; CHECK-NEXT:    adcq %r11, %rcx
+; CHECK-NEXT:    adcq 8(%rsi), %rcx
 ; CHECK-NEXT:    notq %r8
-; CHECK-NEXT:    setb %cl
-; CHECK-NEXT:    movq %r8, %rbx
-; CHECK-NEXT:    adcq %r14, %rbx
-; CHECK-NEXT:    addb $255, %cl
-; CHECK-NEXT:    adcq %r14, %r8
+; CHECK-NEXT:    adcq 16(%rsi), %r8
 ; CHECK-NEXT:    notq %r9
 ; CHECK-NEXT:    adcq 24(%rsi), %r9
-; CHECK-NEXT:    subq %rdx, %r10
 ; CHECK-NEXT:    movq %r10, (%rax)
-; CHECK-NEXT:    movq %rdi, 8(%rax)
-; CHECK-NEXT:    movq %rbx, 16(%rax)
+; CHECK-NEXT:    movq %rcx, 8(%rax)
+; CHECK-NEXT:    movq %r8, 16(%rax)
 ; CHECK-NEXT:    movq %r9, 24(%rax)
-; CHECK-NEXT:    popq %rbx
-; CHECK-NEXT:    .cfi_def_cfa_offset 16
-; CHECK-NEXT:    popq %r14
-; CHECK-NEXT:    .cfi_def_cfa_offset 8
 ; CHECK-NEXT:    retq
 entry:
   %0 = extractvalue %S %arg.b, 0