[PATCH] D29565: [DAGCombiner] (addc X, (adde Y, 0, Carry)) -> (adde X, Y, Carry) when Y + 1 cannot overflow.

[Amaury SECHET via Phabricator via llvm-commits]

deadalnix updated this revision to Diff 87240.
deadalnix added a comment.

Rebase and use computeOverflowKind


https://reviews.llvm.org/D29565

Files:
  lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  test/CodeGen/X86/adde-carry.ll


Index: test/CodeGen/X86/adde-carry.ll
===================================================================
--- test/CodeGen/X86/adde-carry.ll
+++ test/CodeGen/X86/adde-carry.ll
@@ -89,24 +89,21 @@
 define %scalar @pr31719(%scalar* nocapture readonly %this, %scalar %arg.b) {
 ; CHECK-LABEL: pr31719:
 ; CHECK:       # BB#0: # %entry
-; CHECK-NEXT:    addq (%rsi), %rdx
+; CHECK-NEXT:    addq 8(%rsi), %rcx
 ; CHECK-NEXT:    sbbq %r10, %r10
 ; CHECK-NEXT:    andl $1, %r10d
-; CHECK-NEXT:    addq 8(%rsi), %rcx
+; CHECK-NEXT:    addq 16(%rsi), %r8
 ; CHECK-NEXT:    sbbq %rax, %rax
 ; CHECK-NEXT:    andl $1, %eax
-; 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, %r8
-; CHECK-NEXT:    adcq %r10, %r9
+; CHECK-NEXT:    addq (%rsi), %rdx
+; CHECK-NEXT:    adcq $0, %rcx
+; CHECK-NEXT:    adcq %r8, %r10
+; CHECK-NEXT:    adcq %r9, %rax
 ; 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 %r10, 16(%rdi)
+; CHECK-NEXT:    movq %rax, 24(%rdi)
 ; CHECK-NEXT:    movq %rdi, %rax
 ; CHECK-NEXT:    retq
 entry:
Index: lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -1870,6 +1870,17 @@
     return CombineTo(N, DAG.getNode(ISD::ADD, DL, VT, N0, N1),
                      DAG.getNode(ISD::CARRY_FALSE, DL, MVT::Glue));
 
+  // (addc X, (adde Y, 0, Carry)) -> (adde X, Y, Carry)
+  // if Y + 1 cannot overflow.
+  if (N1.getOpcode() == ISD::ADDE && N1->hasOneUse() &&
+      isNullConstant(N1.getOperand(1))) {
+    auto Y = N1.getOperand(0);
+    auto One = DAG.getConstant(1, DL, Y.getValueType());
+    if (DAG.computeOverflowKind(Y, One) == SelectionDAG::OFK_Never)
+      return DAG.getNode(ISD::ADDE, DL, N->getVTList(), N0, Y,
+                         N1.getOperand(2));
+  }
+
   return SDValue();
 }
 


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