[llvm] [AMDGPU] Remove wavefrontsize feature from GFX10+ (PR #98400)

[Matt Arsenault via llvm-commits]

================
@@ -45,10 +45,26 @@ using namespace llvm;
 
 using DecodeStatus = llvm::MCDisassembler::DecodeStatus;
 
+static const MCSubtargetInfo &addDefaultWaveSize(const MCSubtargetInfo &STI,
+                                                 MCContext &Ctx) {
+  if (!STI.hasFeature(AMDGPU::FeatureWavefrontSize64) &&
+      !STI.hasFeature(AMDGPU::FeatureWavefrontSize32)) {
+    MCSubtargetInfo &STICopy = Ctx.getSubtargetCopy(STI);
----------------
arsenm wrote:

Don't really understand this subtargetcopy business 

https://github.com/llvm/llvm-project/pull/98400