[llvm] [SeparateConstOffsetFromGEP] Decompose constant xor operand if possible (PR #150438)

[Matt Arsenault via llvm-commits]

================
@@ -708,11 +715,20 @@ Value *ConstantOffsetExtractor::removeConstOffset(unsigned ChainIndex) {
   Value *NextInChain = removeConstOffset(ChainIndex - 1);
   Value *TheOther = BO->getOperand(1 - OpNo);
 
-  // If NextInChain is 0 and not the LHS of a sub, we can simplify the
-  // sub-expression to be just TheOther.
   if (ConstantInt *CI = dyn_cast<ConstantInt>(NextInChain)) {
-    if (CI->isZero() && !(BO->getOpcode() == Instruction::Sub && OpNo == 0))
-      return TheOther;
+    if (CI->isZero()) {
+      // Custom XOR handling for disjoint bits - preserves original XOR
+      // with non-disjoint constant bits.
+      // TODO: The design should be updated to support partial constant
+      // extraction.
+      if (BO->getOpcode() == Instruction::Xor)
+        return BO;
+
+      // If NextInChain is 0 and not the LHS of a sub, we can simplify the
+      // sub-expression to be just TheOther.
+      if (!(BO->getOpcode() == Instruction::Sub && OpNo == 0))
----------------
arsenm wrote:

push negate through expression 

https://github.com/llvm/llvm-project/pull/150438