[InstCombine] Fold Xor with or disjoint

Implement a missing optimization to fold (A | B) ^ C to (A ^ C) ^ B

Author: AmrDeveloper

llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

@@ -4706,6 +4706,13 @@ Instruction *InstCombinerImpl::visitXor(BinaryOperator &I) {
     return Xor;
 
   Value *X, *Y;
+
+  // (A | B) ^ C -> (A ^ C) ^ B
+  if (match(Op0, m_OneUse(m_c_DisjointOr(m_Value(X), m_Value(Y))))) {
+    Value *XorAC = Builder.CreateXor(X, Op1);
+    return BinaryOperator::CreateXor(XorAC, Y);
+  }
+
   Constant *C1;
   if (match(Op1, m_Constant(C1))) {
     Constant *C2;
@@ -4978,4 +4985,4 @@ Instruction *InstCombinerImpl::visitXor(BinaryOperator &I) {
     return Res;
 
   return nullptr;
-}
+}

llvm/test/Transforms/InstCombine/xor.ll

@@ -1489,8 +1489,8 @@ define i4 @PR96857_xor_without_noundef(i4  %val0, i4  %val1, i4 %val2) {
 define i32 @or_disjoint_with_xor(i32 %a, i32 %b, i32 %c) {
 ; CHECK-LABEL: @or_disjoint_with_xor(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[OR:%.*]] = or disjoint i32 [[A:%.*]], [[B:%.*]]
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[OR]], [[C:%.*]]
+; CHECK-NEXT:    [[TMP0:%.*]] = xor i32 [[A:%.*]], [[C:%.*]]
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[TMP0]], [[B:%.*]]
 ; CHECK-NEXT:    ret i32 [[XOR]]
 ;
 entry:
@@ -1502,8 +1502,8 @@ entry:
 define <2 x i32> @or_disjoint_with_xor_vec(<2 x i32> %a, < 2 x i32> %b, <2 x i32> %c) {
 ; CHECK-LABEL: @or_disjoint_with_xor_vec(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[OR:%.*]] = or disjoint <2 x i32> [[A:%.*]], [[B:%.*]]
-; CHECK-NEXT:    [[XOR:%.*]] = xor <2 x i32> [[OR]], [[C:%.*]]
+; CHECK-NEXT:    [[TMP0:%.*]] = xor <2 x i32> [[A:%.*]], [[C:%.*]]
+; CHECK-NEXT:    [[XOR:%.*]] = xor <2 x i32> [[TMP0]], [[B:%.*]]
 ; CHECK-NEXT:    ret <2 x i32> [[XOR]]
 ;
 entry: