[clang] [llvm] [Dwarf] Support heterogeneous DW_{OP,AT}s needed for AMDGPU CFI (PR #153883)

[Orlando Cazalet-Hyams via llvm-commits]

================
@@ -141,3 +141,9 @@ TEST_F(DWARFExpressionCompactPrinterTest, Test_OP_nop_OP_reg) {
 TEST_F(DWARFExpressionCompactPrinterTest, Test_OP_LLVM_nop_OP_reg) {
   TestExprPrinter({DW_OP_LLVM_user, DW_OP_LLVM_nop, DW_OP_reg0}, "R0");
 }
+
+TEST_F(DWARFExpressionCompactPrinterTest, Test_OP_LLVM_user_unknown_subop) {
+  TestExprPrinter({DW_OP_LLVM_user, DW_OP_LLVM_form_aspace_address},
+                  "<unknown op DW_OP_LLVM_user (233) subop "
+                  "DW_OP_LLVM_form_aspace_address (2)>");
----------------
OCHyams wrote:

I'm sure this has been discussed elsewhere, but out of curiosity why is `DW_OP_LLVM_form_aspace_address` not a `DW_OP_LLVM_user` subop? In the test above it looks like it is, some I'm a bit confused

https://github.com/llvm/llvm-project/pull/153883