[llvm] [AMDGPU] Make SGPR occupancy the exact inverse of getMaxNumSGPRs (PR #201342)

[Janek van Oirschot via llvm-commits]

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@@ -50,6 +53,29 @@ const AMDGPUMCExpr *AMDGPUMCExpr::create(VariantKind Kind,
   return new (Ctx) AMDGPUMCExpr(Kind, Args, Ctx);
 }
 
+unsigned AMDGPUMCExpr::getNumExpectedArgs(VariantKind Kind) {
+  switch (Kind) {
+  case AGVK_None:
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JanekvO wrote:

Should probably bail on `AGVK_None` instead of considering it part of the variadics

https://github.com/llvm/llvm-project/pull/201342