[llvm] [SelectionDAG] Mark frame index as "aliased" at argument copy elison (PR #89712)

[Björn Pettersson via llvm-commits]

================
@@ -11128,14 +11128,15 @@ static void tryToElideArgumentCopy(
   }
 
   // Perform the elision. Delete the old stack object and replace its only use
-  // in the variable info map. Mark the stack object as mutable.
+  // in the variable info map. Mark the stack object as mutable and aliased.
----------------
bjope wrote:

isAliased is used inside ScheduleDAGInstrs.cpp getUnderlyingObjectsForInstr:

```
      if (const PseudoSourceValue *PSV = MMO->getPseudoValue()) {
        // Function that contain tail calls don't have unique PseudoSourceValue
        // objects. Two PseudoSourceValues might refer to the same or
        // overlapping locations. The client code calling this function assumes
        // this is not the case. So return a conservative answer of no known
        // object.
        if (MFI.hasTailCall())
          return false;

        // For now, ignore PseudoSourceValues which may alias LLVM IR values
        // because the code that uses this function has no way to cope with
        // such aliases.
        if (PSV->isAliased(&MFI))
          return false;

        bool MayAlias = PSV->mayAlias(&MFI);
        Objects.emplace_back(PSV, MayAlias);
      } else if (const Value *V = MMO->getValue()) {

```


https://github.com/llvm/llvm-project/pull/89712