[llvm] [ConstantFolding] Support ptrtoaddr in cast folds (PR #162480)

[Alexander Richardson via llvm-commits]

================
@@ -1528,7 +1528,8 @@ Constant *llvm::ConstantFoldCastOperand(unsigned Opcode, Constant *C,
                 Sub->getOpcode() == Instruction::Sub &&
                 Sub->getOperand(0)->isNullValue())
               FoldedValue = ConstantExpr::getSub(
-                  ConstantExpr::getPtrToInt(Ptr, IntIdxTy), Sub->getOperand(1));
+                  ConstantExpr::getCast(Opcode, Ptr, IntIdxTy),
----------------
arichardson wrote:

I am not sure these folds are valid for unstable GC pointers, but since this has been like this for a long time and I have no detailed knowledge of GC pointer support I imagine it's fine.

https://github.com/llvm/llvm-project/pull/162480