[clang] [llvm] [HLSL] Add `Increment`/`DecrementCounter` methods to structured buffers (PR #114148)

[Justin Bogner via llvm-commits]

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@@ -570,3 +780,20 @@ void HLSLExternalSemaSource::CompleteType(TagDecl *Tag) {
     return;
   It->second(Record);
 }
+
+static FunctionDecl *lookupBuiltinFunction(Sema &S, StringRef Name) {
+  IdentifierInfo &II =
+      S.getASTContext().Idents.get(Name, tok::TokenKind::identifier);
+  DeclarationNameInfo NameInfo =
+      DeclarationNameInfo(DeclarationName(&II), SourceLocation());
+  LookupResult R(S, NameInfo, Sema::LookupOrdinaryName);
+  // AllowBuiltinCreation is false but LookupDirect will create
+  // the builtin when searching the global scope anyways...
+  S.LookupName(R, S.getCurScope());
+  // FIXME: If the builtin function was user-declared in global scope,
+  // this assert *will* fail. Should this call LookupBuiltin instead?
+  assert(R.isSingleResult() &&
+         "Since this is a builtin it should always resolve!");
+  assert(isa<FunctionDecl>(R.getFoundDecl()));
+  return cast<FunctionDecl>(R.getFoundDecl());
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bogner wrote:

The assert here is redundant - `cast` does this assert internally

https://github.com/llvm/llvm-project/pull/114148