[PATCH] D57317: [DAGCombine] Deduplicate addcarry node using commutativity.

[Paweł Bylica via Phabricator via llvm-commits]

chfast updated this revision to Diff 464508.
chfast added a comment.
Herald added a subscriber: pengfei.

Rebased.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D57317/new/

https://reviews.llvm.org/D57317

Files:
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  llvm/test/CodeGen/X86/addcarry.ll


Index: llvm/test/CodeGen/X86/addcarry.ll
===================================================================
--- llvm/test/CodeGen/X86/addcarry.ll
+++ llvm/test/CodeGen/X86/addcarry.ll
@@ -1397,13 +1397,10 @@
 define { i64, i64 } @addcarry_commutative_1(i64 %x0, i64 %x1, i64 %y0, i64 %y1) nounwind {
 ; CHECK-LABEL: addcarry_commutative_1:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    movq %rdi, %rax
-; CHECK-NEXT:    addq %rdx, %rax
 ; CHECK-NEXT:    movq %rsi, %rax
-; CHECK-NEXT:    adcq %rcx, %rax
 ; CHECK-NEXT:    addq %rdx, %rdi
-; CHECK-NEXT:    adcq %rcx, %rsi
-; CHECK-NEXT:    movq %rsi, %rdx
+; CHECK-NEXT:    adcq %rcx, %rax
+; CHECK-NEXT:    movq %rax, %rdx
 ; CHECK-NEXT:    retq
   %z0 = call { i64, i1 } @llvm.uadd.with.overflow.i64(i64 %x0, i64 %y0)
   %k0 = extractvalue { i64, i1 } %z0, 1
@@ -1424,13 +1421,10 @@
 define { i64, i64 } @addcarry_commutative_2(i64 %x0, i64 %x1, i64 %y0, i64 %y1) nounwind {
 ; CHECK-LABEL: addcarry_commutative_2:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    movq %rdi, %rax
-; CHECK-NEXT:    addq %rdx, %rax
 ; CHECK-NEXT:    movq %rsi, %rax
-; CHECK-NEXT:    adcq %rcx, %rax
 ; CHECK-NEXT:    addq %rdx, %rdi
-; CHECK-NEXT:    adcq %rcx, %rsi
-; CHECK-NEXT:    movq %rsi, %rdx
+; CHECK-NEXT:    adcq %rcx, %rax
+; CHECK-NEXT:    movq %rax, %rdx
 ; CHECK-NEXT:    retq
   %z0 = call { i64, i1 } @llvm.uadd.with.overflow.i64(i64 %x0, i64 %y0)
   %k0 = extractvalue { i64, i1 } %z0, 1
Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -3056,6 +3056,17 @@
   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();
 }
 


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