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

[Jun Wang via llvm-commits]

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@@ -1426,7 +1425,6 @@ def FeatureISAVersion9_4_Common : FeatureSet<
   [FeatureGFX9,
    FeatureGFX90AInsts,
    FeatureGFX940Insts,
-   FeatureFmaMixInsts,
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jwanggit86 wrote:

The problem was reported for GFX90a -- they noticed presence of v_fma_mix, which is not supposed to occur based on the ISA doc.

As far as GFX90a is concerned, I noticed that v_fma_mix (1) is not in the ISA doc (2) is not supported by sp3. On the other hand, v_mad_mix is the opposite. So it should be fixed, as this PR is trying to do?

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