[llvm-branch-commits] [clang] [llvm] [HLSL][DirectX] Add support for `rootsig` as a target environment (PR #156373)

[Finn Plummer via llvm-branch-commits]

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@@ -1472,5 +1473,38 @@ IdentifierInfo *ParseHLSLRootSignature(Sema &Actions,
   return DeclIdent;
 }
 
+void HandleRootSignatureTarget(Sema &S, StringRef EntryRootSig) {
+  ASTConsumer *Consumer = &S.getASTConsumer();
+
+  // Minimally initalize the parser. This does a couple things:
+  // - initializes Sema scope handling
+  // - invokes HLSLExternalSemaSource
+  // - invokes the preprocessor to lex the macros in the file
+  std::unique_ptr<Parser> P(new Parser(S.getPreprocessor(), S, true));
+  S.getPreprocessor().EnterMainSourceFile();
+
+  bool HaveLexer = S.getPreprocessor().getCurrentLexer();
+  if (HaveLexer) {
+    P->Initialize();
+    S.ActOnStartOfTranslationUnit();
+
+    // Skim through the file to parse to find the define
+    while (P->getCurToken().getKind() != tok::eof)
+      P->ConsumeAnyToken();
+
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inbelic wrote:

For some reason this is required when invoking with `clang-dxc`. Without it the `OBJ` portion of this [test case](https://github.com/llvm/llvm-project/pull/156373/files#diff-38f2db6a18b59091b883cc1c74cbfb3adfe6efb5cf461d146de185844d91cfc9) will fail with an error that `EntryRS` is not defined.

If these lines are removed all other test cases still pass. The other test-cases are all invoked directly with `clang -cc1` and will invoke the [`MacroDefined` callback](https://github.com/llvm/llvm-project/blob/50d72e692c0d45134422956fff10e779ce822b7f/clang/lib/Frontend/FrontendActions.cpp#L1272) during the first lex in `P->Initialize()`.

Perhaps there is some option that `clang-dxc` invokes `clang -cc1` that disables macro expansion before directly needed?

https://github.com/llvm/llvm-project/pull/156373