[clang] [llvm] [Clang][AIX] Add -mloadtime-comment-vars flag to preserve identifying variables (PR #187986)

[Hubert Tong via llvm-commits]

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@@ -0,0 +1,117 @@
+// Test -mloadtime-comment-vars= across a C++20 named-module boundary. Five
+// scenarios, each named by its FileCheck or -verify prefix:
+//
+//   MOD       — the module unit is built to a BMI with the option and then
+//               compiled to IR from the BMI (the two-phase flow build systems
+//               use). Exported, module-linkage, internal-linkage, and inline
+//               variables are all preserved: the implicit attribute is
+//               serialized, and the internal and inline variables reach
+//               CodeGen via the module-initializer list. The same IR is
+//               produced whether or not the option is repeated on the
+//               codegen step: the BMI already records the result.
+//   NOOPT +   — the same module unit built to a BMI without the option and
+//   NOOPTNOT    compiled to IR with it: nothing is preserved. The option
+//               applies to the compilation of the module unit itself, where
+//               semantic analysis runs.
+//   IMPORT +  — an importing TU naming the module-owned variable: the
+//   IMPORTNOT   variable is defined in the module unit, not here, so it is
+//               neither re-emitted nor preserved here, and the module-internal
+//               variable does not leak into the importer. The inline variable
+//               it references is re-emitted here as usual for inline
+//               variables, and that copy is preserved as well because the
+//               attribute travels with the declaration in the BMI.
+//   verify    — specializations instantiated here from the imported template
+//               definitions are diagnosed in this TU, at the pattern location
+//               in the module interface, with a note at the instantiation
+//               point.
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hubert-reinterpretcast wrote:

Prior review comments had already noted that diagnostics should be checked in Sema tests, not CodeGen ones.

https://github.com/llvm/llvm-project/pull/187986