[llvm] [SeparateConstOffsetFromGEP] Decompose constant xor operand if possible (PR #135788)

[Jay Foad via llvm-commits]

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@@ -1162,6 +1202,165 @@ bool SeparateConstOffsetFromGEP::splitGEP(GetElementPtrInst *GEP) {
   return true;
 }
 
+// Helper function to check if an instruction has at least one GEP user
+bool XorToOrDisjointTransformer::hasGEPUser(const Value *V) {
+  for (const User *U : V->users()) {
+    if (isa<GetElementPtrInst>(U)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+bool XorToOrDisjointTransformer::dominatesAllXors(
+    BinaryOperator *BaseXor, const XorOpList &XorsInGroup) {
+  for (const auto &XorEntry : XorsInGroup) {
+    BinaryOperator *XorInst = XorEntry.first;
+    if (XorInst != BaseXor && !DT.dominates(BaseXor, XorInst)) {
+      return false;
+    }
+  }
+  return true;
+}
+
+bool XorToOrDisjointTransformer::processXorGroup(Instruction *OriginalBaseInst,
+                                                 XorOpList &XorsInGroup) {
+  bool Changed = false;
+  if (XorsInGroup.size() <= 1)
+    return false;
+
+  // Sort XorsInGroup by the constant offset value in increasing order.
+  llvm::sort(
+      XorsInGroup.begin(), XorsInGroup.end(),
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jayfoad wrote:

I thought the point of `llvm::sort` was that you can pass in a range instead of begin and end.

https://github.com/llvm/llvm-project/pull/135788