[llvm] [DAGCombine] Add all users of the instruction recursively into worklist when an instruction is simplified (PR #91772)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-x86

Author: Shengchen Kan (KanRobert)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/91772.diff


2 Files Affected:

- (modified) llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (+3-1) 
- (modified) llvm/test/CodeGen/X86/addcarry.ll (+8-21) 


``````````diff
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 4589d201d6203..796264394c046 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -205,8 +205,10 @@ namespace {
     /// When an instruction is simplified, add all users of the instruction to
     /// the work lists because they might get more simplified now.
     void AddUsersToWorklist(SDNode *N) {
-      for (SDNode *Node : N->uses())
+      for (SDNode *Node : N->uses()) {
         AddToWorklist(Node);
+        AddUsersToWorklist(Node);
+      }
     }
 
     /// Convenient shorthand to add a node and all of its user to the worklist.
diff --git a/llvm/test/CodeGen/X86/addcarry.ll b/llvm/test/CodeGen/X86/addcarry.ll
index f8d32fc2d2925..3895d3a51b366 100644
--- a/llvm/test/CodeGen/X86/addcarry.ll
+++ b/llvm/test/CodeGen/X86/addcarry.ll
@@ -317,21 +317,13 @@ define %S @readd(ptr nocapture readonly %this, %S %arg.b) nounwind {
 ; CHECK:       # %bb.0: # %entry
 ; CHECK-NEXT:    movq %rdi, %rax
 ; CHECK-NEXT:    addq (%rsi), %rdx
-; CHECK-NEXT:    movq 8(%rsi), %rdi
-; CHECK-NEXT:    adcq $0, %rdi
-; CHECK-NEXT:    setb %r10b
-; CHECK-NEXT:    movzbl %r10b, %r10d
-; CHECK-NEXT:    addq %rcx, %rdi
-; CHECK-NEXT:    adcq 16(%rsi), %r10
-; CHECK-NEXT:    setb %cl
-; CHECK-NEXT:    movzbl %cl, %ecx
-; CHECK-NEXT:    addq %r8, %r10
-; CHECK-NEXT:    adcq 24(%rsi), %rcx
-; CHECK-NEXT:    addq %r9, %rcx
-; CHECK-NEXT:    movq %rdx, (%rax)
-; CHECK-NEXT:    movq %rdi, 8(%rax)
-; CHECK-NEXT:    movq %r10, 16(%rax)
-; CHECK-NEXT:    movq %rcx, 24(%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 %r8, 16(%rdi)
+; CHECK-NEXT:    movq %r9, 24(%rdi)
 ; CHECK-NEXT:    retq
 entry:
   %0 = extractvalue %S %arg.b, 0
@@ -422,14 +414,9 @@ define i128 @addcarry_to_subcarry(i64 %a, i64 %b) nounwind {
 ; CHECK:       # %bb.0:
 ; CHECK-NEXT:    movq %rdi, %rax
 ; CHECK-NEXT:    cmpq %rsi, %rdi
-; CHECK-NEXT:    notq %rsi
+; CHECK-NEXT:    sbbq %rsi, %rax
 ; CHECK-NEXT:    setae %cl
-; CHECK-NEXT:    addb $-1, %cl
-; CHECK-NEXT:    adcq $0, %rax
-; CHECK-NEXT:    setb %cl
 ; CHECK-NEXT:    movzbl %cl, %edx
-; CHECK-NEXT:    addq %rsi, %rax
-; CHECK-NEXT:    adcq $0, %rdx
 ; CHECK-NEXT:    retq
   %notb = xor i64 %b, -1
   %notb128 = zext i64 %notb to i128

``````````

</details>


https://github.com/llvm/llvm-project/pull/91772