[clang] [llvm] [HLSL][RootSignature] Implement parsing of a DescriptorTable with empty clauses (PR #133302)

[via llvm-commits]

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@@ -0,0 +1,188 @@
+#include "clang/Parse/ParseHLSLRootSignature.h"
+
+#include "llvm/Support/raw_ostream.h"
+
+using namespace llvm::hlsl::rootsig;
+
+namespace clang {
+namespace hlsl {
+
+static std::string FormatTokenKinds(ArrayRef<TokenKind> Kinds) {
+  std::string TokenString;
+  llvm::raw_string_ostream Out(TokenString);
+  bool First = true;
+  for (auto Kind : Kinds) {
+    if (!First)
+      Out << ", ";
+    switch (Kind) {
+#define TOK(X, SPELLING)                                                       \
+  case TokenKind::X:                                                           \
+    Out << SPELLING;                                                           \
+    break;
+#include "clang/Lex/HLSLRootSignatureTokenKinds.def"
+    }
+    First = false;
+  }
+
+  return TokenString;
+}
+
+// Parser Definitions
+
+RootSignatureParser::RootSignatureParser(SmallVector<RootElement> &Elements,
+                                         RootSignatureLexer &Lexer,
+                                         Preprocessor &PP)
+    : Elements(Elements), Lexer(Lexer), PP(PP), CurToken(SourceLocation()) {}
+
+bool RootSignatureParser::Parse() {
+  // Iterate as many RootElements as possible
+  while (TryConsumeExpectedToken(TokenKind::kw_DescriptorTable)) {
+    bool Error = false;
+    // Dispatch onto parser method.
+    // We guard against the unreachable here as we just ensured that CurToken
+    // will be one of the kinds in the while condition
+    switch (CurToken.Kind) {
+    case TokenKind::kw_DescriptorTable:
+      Error = ParseDescriptorTable();
+      break;
+    default:
+      llvm_unreachable("Switch for consumed token was not provided");
+    }
+
+    if (Error)
+      return true;
+
+    if (!TryConsumeExpectedToken(TokenKind::pu_comma))
+      break;
+  }
+
+  return ConsumeExpectedToken(TokenKind::end_of_stream, diag::err_expected);
+}
+
+bool RootSignatureParser::ParseDescriptorTable() {
+  assert(CurToken.Kind == TokenKind::kw_DescriptorTable &&
+         "Expects to only be invoked starting at given keyword");
+
+  DescriptorTable Table;
+
+  if (ConsumeExpectedToken(TokenKind::pu_l_paren, diag::err_expected_after,
+                           CurToken.Kind))
+    return true;
+
+  // Iterate as many Clauses as possible
+  while (TryConsumeExpectedToken({TokenKind::kw_CBV, TokenKind::kw_SRV,
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joaosaffran wrote:

nit: I imagine the above loop would be something like this, once you add more Root Elements?

https://github.com/llvm/llvm-project/pull/133302