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

[Finn Plummer via llvm-commits]

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@@ -0,0 +1,110 @@
+//===--- ParseHLSLRootSignature.h -------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file defines the ParseHLSLRootSignature interface.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_PARSE_PARSEHLSLROOTSIGNATURE_H
+#define LLVM_CLANG_PARSE_PARSEHLSLROOTSIGNATURE_H
+
+#include "clang/Basic/DiagnosticParse.h"
+#include "clang/Lex/LexHLSLRootSignature.h"
+#include "clang/Lex/Preprocessor.h"
+
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringRef.h"
+
+#include "llvm/Frontend/HLSL/HLSLRootSignature.h"
+
+namespace clang {
+namespace hlsl {
+
+class RootSignatureParser {
+public:
+  RootSignatureParser(SmallVector<llvm::hlsl::rootsig::RootElement> &Elements,
+                      RootSignatureLexer &Lexer, clang::Preprocessor &PP);
+
+  /// Consumes tokens from the Lexer and constructs the in-memory
+  /// representations of the RootElements. Tokens are consumed until an
+  /// error is encountered or the end of the buffer.
+  ///
+  /// Returns true if a parsing error is encountered.
+  bool Parse();
+
+private:
+  DiagnosticsEngine &Diags() { return PP.getDiagnostics(); }
+
+  // All private Parse.* methods follow a similar pattern:
+  //   - Each method will start with an assert to denote what the CurToken is
+  // expected to be and will parse from that token forward
+  //
+  //   - Therefore, it is the callers responsibility to ensure that you are
+  // at the correct CurToken. This should be done with the pattern of:
+  //
+  //  if (TryConsumeExpectedToken(TokenKind))
+  //    if (Parse.*())
+  //      return true;
+  //
+  // or,
+  //
+  //  if (ConsumeExpectedToken(TokenKind, ...))
+  //    return true;
+  //  if (Parse.*())
+  //    return true;
+  //
+  //   - All methods return true if a parsing error is encountered. It is the
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inbelic wrote:

Is it clear here that methods is the `Parse.*` methods?

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