[llvm-branch-commits] [flang] [flang][OpenMP] Use new modifiers in IF/LASTPRIVATE (PR #118128)

[Krzysztof Parzyszek via llvm-branch-commits]

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@@ -16,13 +16,58 @@
 #include "token-parsers.h"
 #include "type-parser-implementation.h"
 #include "flang/Parser/parse-tree.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Frontend/OpenMP/OMP.h"
 
 // OpenMP Directives and Clauses
 namespace Fortran::parser {
 
 constexpr auto startOmpLine = skipStuffBeforeStatement >> "!$OMP "_sptok;
 constexpr auto endOmpLine = space >> endOfLine;
 
+/// Parse OpenMP directive name (this includes compound directives).
+struct OmpDirectiveNameParser {
+  using resultType = llvm::omp::Directive;
+  using Token = TokenStringMatch<false, false>;
+
+  std::optional<resultType> Parse(ParseState &state) const {
+    for (const NameWithId &nid : directives()) {
+      if (attempt(Token(nid.first.data())).Parse(state)) {
+        return nid.second;
+      }
+    }
+    return std::nullopt;
+  }
+
+private:
+  using NameWithId = std::pair<std::string, llvm::omp::Directive>;
+
+  llvm::iterator_range<const NameWithId *> directives() const;
+  void initTokens(NameWithId *) const;
+};
+
+llvm::iterator_range<const OmpDirectiveNameParser::NameWithId *>
+OmpDirectiveNameParser::directives() const {
+  static NameWithId table[llvm::omp::Directive_enumSize];
+  [[maybe_unused]] static bool init = (initTokens(table), true);
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kparzysz wrote:

The issue here is with thread-safety.  Starting with C++11, the standard guarantees that local statics are initialized in a thread-safe manner, that is, that the initializer code is only executed by a single thread.  Hence the "trick" is to make the preparation of a local static be a part of the initializer.  This is a de facto standard in the LLVM code, although I didn't see it mentioned in the coding guidelines.  It's somewhat rare, but within the set of use cases it's the preferred solution.

https://github.com/llvm/llvm-project/pull/118128