[llvm] [AMDGPU][GlobalIsel] Use isRegisterClassType to check for legal types for G_FREEZE & G_IMPLICIT_DEF (PR #101331)

[Matt Arsenault via llvm-commits]

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@@ -889,10 +890,13 @@ AMDGPULegalizerInfo::AMDGPULegalizerInfo(const GCNSubtarget &ST_,
     .clampScalar(0, S16, S64);
 
   getActionDefinitionsBuilder({G_IMPLICIT_DEF, G_FREEZE})
-      .legalIf(isRegisterType(0))
+      // s1 and s16 are special cases because they have legal operations on
+      // them, but don't really occupy registers in the normal way.
+      .legalIf(isRegisterClassType(0))
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arsenm wrote:

Why do we have both "isRegisterType" and "isRegisterClassType"?

https://github.com/llvm/llvm-project/pull/101331