[clang] [HLSL] Rewrite semantics parsing (PR #152537)

[Nathan Gauër via cfe-commits]

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@@ -232,6 +232,41 @@ class HLSLAnnotationAttr : public InheritableAttr {
   }
 };
 
+class HLSLSemanticAttr : public HLSLAnnotationAttr {
+  unsigned SemanticIndex : 30;
+  LLVM_PREFERRED_TYPE(bool)
+  unsigned SemanticIndexable : 1;
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Keenuts wrote:

I wanted specifically to avoid having the indexing logic somewhere else in the code: make the TD file defines the rules allowed for a given semantic. But we could also do this as you suggested. I'll reserve this change to the refactoring of the conditions (like what value is allowed for what semantic, etc)

https://github.com/llvm/llvm-project/pull/152537