[llvm] [InstCombine] Fold `(A | B) ^ (A & C) --> A ? ~C : B` (PR #121906)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Yingwei Zheng (dtcxzyw)

<details>
<summary>Changes</summary>

Closes https://github.com/llvm/llvm-project/issues/121773.


---
Full diff: https://github.com/llvm/llvm-project/pull/121906.diff


2 Files Affected:

- (modified) llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp (+2-2) 
- (modified) llvm/test/Transforms/InstCombine/xor-and-or.ll (+12) 


``````````diff
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index 37a7c4d88b234d..d8fd41de47869b 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -4972,8 +4972,8 @@ Instruction *InstCombinerImpl::visitXor(BinaryOperator &I) {
 
   // (A & B) ^ (A | C) --> A ? ~B : C -- There are 4 commuted variants.
   if (I.getType()->isIntOrIntVectorTy(1) &&
-      match(Op0, m_OneUse(m_LogicalAnd(m_Value(A), m_Value(B)))) &&
-      match(Op1, m_OneUse(m_LogicalOr(m_Value(C), m_Value(D))))) {
+      match(&I, m_c_Xor(m_OneUse(m_LogicalAnd(m_Value(A), m_Value(B))),
+                        m_OneUse(m_LogicalOr(m_Value(C), m_Value(D)))))) {
     bool NeedFreeze = isa<SelectInst>(Op0) && isa<SelectInst>(Op1) && B == D;
     if (B == C || B == D)
       std::swap(A, B);
diff --git a/llvm/test/Transforms/InstCombine/xor-and-or.ll b/llvm/test/Transforms/InstCombine/xor-and-or.ll
index 47275ce31070b5..c380e2748f89bc 100644
--- a/llvm/test/Transforms/InstCombine/xor-and-or.ll
+++ b/llvm/test/Transforms/InstCombine/xor-and-or.ll
@@ -25,6 +25,18 @@ define i1 @xor_logic_and_logic_or2(i1 %c, i1 %x, i1 %y) {
   ret i1 %r
 }
 
+define i1 @xor_logic_and_logic_or2_commuted(i1 %c, i1 %x, i1 %y) {
+; CHECK-LABEL: @xor_logic_and_logic_or2_commuted(
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i1 [[X:%.*]], true
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[C:%.*]], i1 [[TMP1]], i1 [[Y:%.*]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %o = select i1 %y, i1 true, i1 %c
+  %a = select i1 %c, i1 %x, i1 false
+  %r = xor i1 %o, %a
+  ret i1 %r
+}
+
 define i1 @xor_logic_and_logic_or3(i1 %c, i1 %x, i1 %y) {
 ; CHECK-LABEL: @xor_logic_and_logic_or3(
 ; CHECK-NEXT:    [[TMP1:%.*]] = freeze i1 [[C:%.*]]

``````````

</details>


https://github.com/llvm/llvm-project/pull/121906