[llvm] [AMDGPU][MC]FMA-mix instructions should not be supported in GFX908 etc. (PR #109873)

[Stanislav Mekhanoshin via llvm-commits]

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@@ -1426,7 +1425,6 @@ def FeatureISAVersion9_4_Common : FeatureSet<
   [FeatureGFX9,
    FeatureGFX90AInsts,
    FeatureGFX940Insts,
-   FeatureFmaMixInsts,
----------------
rampitec wrote:

I think we shall not change it. This is quite unfortunate mess in the asm, but that is what really happened in Vega 12 and then carried forward to later gfx9 based products (at least according to the documentation):

MAD_MIXLO_F16/MAD_MIXHI_F16/MAD_MIX_F32 used to be Mad f32 based before, and FMA based on all later chips.

The most important statement there: "Name not changed".

So it is the same encoding, but different instructions before and after gfx906. Unfortunately, SP3 decided to preserve the name. I do not think we shall follow.

That said, run lines for gfx908 can be added to mad-mix*.ll tests and I believe shall use fma_mix.



https://github.com/llvm/llvm-project/pull/109873