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

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skc7 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 [Fixing Rust build #1](https://github.com/llvm/llvm-project/pull/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`.

Hi @hctim, #68865 has been updated as per suggestions. Please review.

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