[clang] [llvm] [HLSL][RootSignature] Add infastructure to parse parameters (PR #133800)

[Chris B via cfe-commits]

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@@ -89,37 +88,178 @@ bool RootSignatureParser::parseDescriptorTableClause() {
           CurToken.TokKind == TokenKind::kw_UAV ||
           CurToken.TokKind == TokenKind::kw_Sampler) &&
          "Expects to only be invoked starting at given keyword");
+  TokenKind ParamKind = CurToken.TokKind; // retain for diagnostics
 
   DescriptorTableClause Clause;
-  switch (CurToken.TokKind) {
+  TokenKind ExpectedRegister;
+  switch (ParamKind) {
   default:
     llvm_unreachable("Switch for consumed token was not provided");
   case TokenKind::kw_CBV:
     Clause.Type = ClauseType::CBuffer;
+    ExpectedRegister = TokenKind::bReg;
     break;
   case TokenKind::kw_SRV:
     Clause.Type = ClauseType::SRV;
+    ExpectedRegister = TokenKind::tReg;
     break;
   case TokenKind::kw_UAV:
     Clause.Type = ClauseType::UAV;
+    ExpectedRegister = TokenKind::uReg;
     break;
   case TokenKind::kw_Sampler:
     Clause.Type = ClauseType::Sampler;
+    ExpectedRegister = TokenKind::sReg;
     break;
   }
 
   if (consumeExpectedToken(TokenKind::pu_l_paren, diag::err_expected_after,
-                           CurToken.TokKind))
+                           ParamKind))
     return true;
 
-  if (consumeExpectedToken(TokenKind::pu_r_paren, diag::err_expected_after,
-                           CurToken.TokKind))
+  llvm::SmallDenseMap<TokenKind, ParamType> Params = {
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llvm-beanz wrote:

Hypothetically, based on the grammar what is the maximum number of token->param mappings we could have here?

The reason I'm asking: is it better to have a map with dynamic allocations and lookup, or just a struct full of optionals to serve as the state?

https://github.com/llvm/llvm-project/pull/133800