[llvm] [Utils][SPIR-V] Adding spirv-sim to LLVM (PR #107094)

[Nathan Gauër via llvm-commits]

Keenuts wrote:

> > Currently, the testing infrastructure for SPIR-V is based on FileCheck. Those tests are great to check some level of codegen, but when the test needs check both the CFG layout and the content of each basic-block, things becomes messy.
> > Because the CHECK/CHECK-DAG/CHECK-NEXT state is limited, it is sometimes hard to catch the good block: if 2 basic blocks have similar instructions, FileCheck can match the wrong one.
> > Cross-lane interaction can be a bit difficult to understand, and writting a FileCheck test that is strong enough to catch bad CFG transforms while not being broken everytime some unrelated codegen part changes is hard.
> 
> I have quite some concerns with this line of arguments: this seems to go against the way virtually **all** of LLVM is currently tested. While this seems like a valuable discussion to have, I see this as a major departure from the current testing approach, and as such this needs a clear RFC on the Discourse forum about the kind of testing we expect in LLVM (unit-testing vs integration tests) and all the associated tradeoffs.
> 
> In the meantime, please don't consider this as a valid alternative to unit-test / FileCheck tests.
> 
> (if this RFC / discussion already happened and I missed it, then please just point me to the discussion :) )

Hi Mehdi!
There was no discourse thread, we discussed that in the LLVM SPIR-V backend meetings (each monday).
Yes, this is a different method, and I can see why some would disagree. I'll open a discourse thread so we can have a discussion in a more suited place then.

(FYI @michalpaszkowski @s-perron )

https://github.com/llvm/llvm-project/pull/107094