return DAG.getNode(ISD::ADDCARRY, SDLoc(N), N->getVTList(),
N0.getOperand(0), N0.getOperand(1), CarryIn);
+ /**
+ * When one of the addcarry argument is itself a carry, we may be facing
+ * a diamond carry propagation. In which case we try to transform the DAG
+ * to ensure linear carry propagation if that is possible.
+ *
+ * We are trying to get:
+ * (addcarry X, 0, (addcarry A, B, Z):Carry)
+ */
+ if (auto Y = getAsCarry(TLI, N1)) {
+ /**
+ * (uaddo A, B)
+ * / \
+ * Carry Sum
+ * | \
+ * | (addcarry *, 0, Z)
+ * | /
+ * \ Carry
+ * | /
+ * (addcarry X, *, *)
+ */
+ if (Y.getOpcode() == ISD::UADDO &&
+ CarryIn.getResNo() == 1 &&
+ CarryIn.getOpcode() == ISD::ADDCARRY &&
+ isNullConstant(CarryIn.getOperand(1)) &&
+ CarryIn.getOperand(0) == Y.getValue(0)) {
+ auto NewY = DAG.getNode(ISD::ADDCARRY, SDLoc(N), Y->getVTList(),
+ Y.getOperand(0), Y.getOperand(1),
+ CarryIn.getOperand(2));
+ AddToWorklist(NewY.getNode());
+ return DAG.getNode(ISD::ADDCARRY, SDLoc(N), N->getVTList(), N0,
+ DAG.getConstant(0, SDLoc(N), N0.getValueType()),
+ NewY.getValue(1));
+ }
+ }
+
return SDValue();
}
define %scalar @pr31719(%scalar* nocapture readonly %this, %scalar %arg.b) {
; CHECK-LABEL: pr31719:
; CHECK: # BB#0: # %entry
-; CHECK-NEXT: xorl %r10d, %r10d
-; CHECK-NEXT: addq 8(%rsi), %rcx
-; CHECK-NEXT: setb %r10b
-; CHECK-NEXT: xorl %eax, %eax
-; CHECK-NEXT: addq 16(%rsi), %r8
-; CHECK-NEXT: setb %al
-; CHECK-NEXT: addq 24(%rsi), %r9
; CHECK-NEXT: addq (%rsi), %rdx
-; CHECK-NEXT: adcq $0, %rcx
-; CHECK-NEXT: adcq %r8, %r10
-; CHECK-NEXT: adcq %r9, %rax
+; CHECK-NEXT: adcq 8(%rsi), %rcx
+; CHECK-NEXT: adcq 16(%rsi), %r8
+; CHECK-NEXT: adcq 24(%rsi), %r9
; CHECK-NEXT: movq %rdx, (%rdi)
; CHECK-NEXT: movq %rcx, 8(%rdi)
-; CHECK-NEXT: movq %r10, 16(%rdi)
-; CHECK-NEXT: movq %rax, 24(%rdi)
+; CHECK-NEXT: movq %r8, 16(%rdi)
+; CHECK-NEXT: movq %r9, 24(%rdi)
; CHECK-NEXT: movq %rdi, %rax
; CHECK-NEXT: retq
entry: