[PATCH] D106315: [HIP] Preserve ASAN bitcode library functions

[Yaxun Liu via Phabricator via cfe-commits]

yaxunl added a comment.

In D106315#2900882 <https://reviews.llvm.org/D106315#2900882>, @tra wrote:

> In D106315#2899928 <https://reviews.llvm.org/D106315#2899928>, @yaxunl wrote:
>
>> Yes that's possible. However that would require FE to know these functions and declare them, whereas the current approach leave the concern to the device library.
>
> I was thinking of just adding a pointer to an array of pointers to `@llvm.compiler.used`.
> The array itself would come from the bitcode library and would be populated there.  I'm not sure if it's doable without knowing the array size, though.
>
> e.g
>
>   ; Added by compiler
>   @llvm.compiler.used = appending global [1 x i8*] [i8* bitcast ([16 x i8*]* @_ZL5funcs to i8*)], section "llvm.metadata"
>   
>   ; comes from the bitcode library, initialized with the pointers to functions you need to keep.
>   @_ZL5funcs = internal global [16 x i8*] zeroinitializer, align 4
>
> It should be possible to make the pointer to the array opaque with an intermadiate variable in the library.

Yes that is possible. Actually it can be simpler. We can add `__attribute__((used))` to the dummy function in the bitcode lib, and it will be kept when linked by -mlink-builtin-bitcode.

However, it has a drawback compared to the current approach. It has no control when to keep the dummy function, whereas the current approach only keep it for -fsanitize=asan.


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