[clang] [llvm] [ASAN] For Asan instrumented global, emit two symbols, one with actual size and other with instrumented size. (PR #70166)

[Mitch Phillips via cfe-commits]

hctim wrote:

Will wait for a rebase on some changes requested in #68865, but it'd also be really important to write tests for a couple more scenarios:

 1. Building with `-fsanitize=address -S -emit-llvm` results in GVs with `sanitized_padded_global` (and results in GVs without `sanitized_padded_global` if they have `__attribute__((no_sanitize("address")))` for example). See `clang/test/CodeGen/memtag-globals.cpp`.
 2. Running #1 through bitcode back/forth to make sure you still have the same attributes sets (to ensure you got the parser/writer logic correct). See `llvm/test/Bitcode/compatibility.ll` and `llvm/test/Assembler/globalvariable-attributes.ll`.


https://github.com/llvm/llvm-project/pull/70166