[compiler-rt] [llvm] [RFC][Transforms][IPO] Add func suffix in ArgumentPromotion and DeadArgumentElimination (PR #109899)

[Snehasish Kumar via llvm-commits]

snehasish wrote:

There are downstream (internal) usages which rely on function names as they exist in the symbol table. Memprof relies on the dwarf linkage name so it's usage is similar to llvm-profgen. In the past, suffixes after a period in the symbol were meant to be interpreted as clones of the original function, however it is not well defined. 

Personally, I'm not in favour of overloading the existing  usage by appending suffixes to indicate the optimizations performed. This seems to be a hacky approach and instead we should adopt a more formal mechanism to communicate such information to external tools. As @mtrofin  suggested it would be a good to start an RFC discussion on discourse to gather the different usages from a broader set of users than those on this patch before proceeding.

Since not all suffixes are the same, key  considerations for the discourse RFC could be - 
* when the symbol name changes 
 clang backend e.g. `-funiq-internal-linkage-name`
 LLVM IR -  function specialization
 ThinLTO promotion 
 Backend - Propeller / FDO based function splitting
* what do the suffixes imply (clones, modifications, parts etc)
* how should debuggers and profiling tools treat the symbols

Some of these were discussed piecemeal in #105742 however a broader discussion could be beneficial. What do you think?

https://github.com/llvm/llvm-project/pull/109899