[llvm] [Frontend][OpenMP] Implement directive name parser (PR #146776)

[Alexey Bataev via llvm-commits]

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@@ -0,0 +1,93 @@
+//===- DirectiveNameParser.cpp --------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Frontend/OpenMP/DirectiveNameParser.h"
+#include "llvm/Frontend/OpenMP/OMP.h"
+
+#include <cassert>
+#include <memory>
+
+namespace llvm::omp {
+DirectiveNameParser::DirectiveNameParser(SourceLanguage L) {
+  // Take every directive, get its name in every version, break the name up
+  // into whitespace-separated tokens, and insert each token.
+  for (size_t I = 0, E = Directive_enumSize; I != E; ++I) {
+    auto D = static_cast<Directive>(I);
+    if (D == Directive::OMPD_unknown || !(getDirectiveLanguages(D) & L))
+      continue;
+    for (unsigned Ver : getOpenMPVersions())
+      insertName(getOpenMPDirectiveName(D, Ver), D);
+  }
+}
+
+const DirectiveNameParser::State *
+DirectiveNameParser::apply(const State *Current, StringRef Tok) const {
+  if (!Current)
+    return Current;
+  assert(Current->isValid() && "Invalid input state");
+  if (const State *Next = const_cast<State *>(Current)->next(Tok))
+    return Next->isValid() ? Next : nullptr;
+  return nullptr;
+}
+
+SmallVector<StringRef> DirectiveNameParser::tokenize(StringRef Str) {
+  SmallVector<StringRef> Tokens;
+
+  auto nextChar = [](StringRef N, size_t I) {
+    while (I < N.size() && N[I] == ' ')
+      ++I;
+    return I;
+  };
+  auto nextSpace = [](StringRef N, size_t I) {
+    size_t S = N.find(' ', I);
+    return S != StringRef::npos ? S : N.size();
+  };
+
+  size_t From = nextChar(Str, 0);
+  size_t To = 0;
+
+  while (From != Str.size()) {
+    To = nextSpace(Str, From);
+    Tokens.push_back(Str.substr(From, To - From));
+    From = nextChar(Str, To);
+  }
+
+  return Tokens;
+}
+
+void DirectiveNameParser::insertName(StringRef Name, Directive D) {
+  State *Where = &InitialState;
+
+  for (StringRef Tok : tokenize(Name))
+    Where = insertTransition(Where, Tok);
+
+  Where->Value = D;
+}
+
+DirectiveNameParser::State *
+DirectiveNameParser::insertTransition(State *From, StringRef Tok) {
+  assert(From && "Expecting state");
+  if (!From->Transition) {
+    From->Transition = std::make_unique<State::TransitionMapTy>();
+  }
+  if (State *Next = From->next(Tok))
+    return Next;
+
+  auto [Where, DidIt] = From->Transition->try_emplace(Tok, State());
+  assert(DidIt && "Map insertion failed");
+  return &Where->second;
+}
+
+DirectiveNameParser::State *DirectiveNameParser::State::next(StringRef Tok) {
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alexey-bataev wrote:

Can it be made const?

https://github.com/llvm/llvm-project/pull/146776