[flang-commits] [clang] [flang] [llvm] [X86][AVX10] Remove EVEX512 and AVX10-256 implementations (PR #157034)

[Phoebe Wang via flang-commits]

phoebewang wrote:

> For the future, I wonder if we can avoid breaking changes like this and instead make the deprecated flags and targets no-ops. It is not just a matter of passing -mavx10.1-512 flags or not.
> 
> For dynamic dispatch, we have had to specify "evex512" attributes in code, and that has now transitioned from required to build-breaking. Because we are not only dealing with discrete clang releases, such behavior changes are quite painful.
> 
> It would help to add some way to detect from code whether the breaking change has occurred, for example a builtin `#define`.

SW has to match with HW spec, so it's unavoidable sometimes when HW changed. We have tried to reduce the disturbance. So "evex512" turns to a no-op. "avx10.1-512" and "avx10.1-512" are aliases of "avx10.1" and "avx10.2". However, "no-evex512", "avx10.1-256" and "avx10.2-256" have no substitutable solutions because we don't have HW support.

https://github.com/llvm/llvm-project/pull/157034