[llvm] AMDGPU: Clean up more real instruction predicate overrides (PR #116868)

[Matt Arsenault via llvm-commits]

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@@ -709,7 +708,7 @@ multiclass MAIInst<string OpName, string P, SDPatternOperator node> {
                                  !if(!eq(node, null_frag), null_frag, AgprMAIFrag<node>)>,
                          MFMATable<1, NAME # "_e64">;
 
-        let SubtargetPredicate = isGFX90APlus in
+        let OtherPredicates = [isGFX90APlus] in
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arsenm wrote:

The VGPR encoded version was only added in 90a, this was always the restriction. The inner let is still a bit of a hack, but it's at least more local now 

https://github.com/llvm/llvm-project/pull/116868