[clang-tidy] openmp-use-default-none - a new check

Summary:
Finds OpenMP directives that are allowed to contain `default` clause,
but either don't specify it, or the clause is specified but with the kind
other than `none`, and suggests to use `default(none)` clause.

Using `default(none)` clause changes the default variable visibility from
being implicitly determined, and thus forces developer to be explicit about the
desired data scoping for each variable.

Reviewers: JonasToth, aaron.ballman, xazax.hun, hokein, gribozavr

Reviewed By: JonasToth, aaron.ballman

Subscribers: jdoerfert, openmp-commits, klimek, sbenza, arphaman, Eugene.Zelenko, ABataev, mgorny, rnkovacs, guansong, cfe-commits

Tags: #clang-tools-extra, #openmp, #clang

Differential Revision: https://reviews.llvm.org/D57113

llvm-svn: 356801

clang-tools-extra/clang-tidy/openmp/CMakeLists.txt

@@ -2,6 +2,7 @@ set(LLVM_LINK_COMPONENTS support)
 
 add_clang_library(clangTidyOpenMPModule
   OpenMPTidyModule.cpp
+  UseDefaultNoneCheck.cpp
 
   LINK_LIBS
   clangAST

clang-tools-extra/clang-tidy/openmp/OpenMPTidyModule.cpp

@@ -9,6 +9,7 @@
 #include "../ClangTidy.h"
 #include "../ClangTidyModule.h"
 #include "../ClangTidyModuleRegistry.h"
+#include "UseDefaultNoneCheck.h"
 
 namespace clang {
 namespace tidy {
@@ -18,6 +19,8 @@ namespace openmp {
 class OpenMPModule : public ClangTidyModule {
 public:
   void addCheckFactories(ClangTidyCheckFactories &CheckFactories) override {
+    CheckFactories.registerCheck<UseDefaultNoneCheck>(
+        "openmp-use-default-none");
   }
 };
 

clang-tools-extra/clang-tidy/openmp/UseDefaultNoneCheck.cpp

@@ -0,0 +1,65 @@
+//===--- UseDefaultNoneCheck.cpp - clang-tidy -----------------------------===//
+//
+// 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 "UseDefaultNoneCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/OpenMPClause.h"
+#include "clang/AST/Stmt.h"
+#include "clang/AST/StmtOpenMP.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/ASTMatchers/ASTMatchersMacros.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace openmp {
+
+void UseDefaultNoneCheck::registerMatchers(MatchFinder *Finder) {
+  // Don't register the check if OpenMP is not enabled; the OpenMP pragmas are
+  // completely ignored then, so no OpenMP entires will be present in the AST.
+  if (!getLangOpts().OpenMP)
+    return;
+
+  Finder->addMatcher(
+      ompExecutableDirective(
+          allOf(isAllowedToContainClauseKind(OMPC_default),
+                anyOf(unless(hasAnyClause(ompDefaultClause())),
+                      hasAnyClause(ompDefaultClause(unless(isNoneKind()))
+                                       .bind("clause")))))
+          .bind("directive"),
+      this);
+}
+
+void UseDefaultNoneCheck::check(const MatchFinder::MatchResult &Result) {
+  const auto *Directive =
+      Result.Nodes.getNodeAs<OMPExecutableDirective>("directive");
+  assert(Directive != nullptr && "Expected to match some directive.");
+
+  if (const auto *Clause = Result.Nodes.getNodeAs<OMPDefaultClause>("clause")) {
+    diag(Directive->getBeginLoc(),
+         "OpenMP directive '%0' specifies 'default(%1)' clause, consider using "
+         "'default(none)' clause instead")
+        << getOpenMPDirectiveName(Directive->getDirectiveKind())
+        << getOpenMPSimpleClauseTypeName(Clause->getClauseKind(),
+                                         Clause->getDefaultKind());
+    diag(Clause->getBeginLoc(), "existing 'default' clause specified here",
+         DiagnosticIDs::Note);
+    return;
+  }
+
+  diag(Directive->getBeginLoc(),
+       "OpenMP directive '%0' does not specify 'default' clause, consider "
+       "specifying 'default(none)' clause")
+      << getOpenMPDirectiveName(Directive->getDirectiveKind());
+}
+
+} // namespace openmp
+} // namespace tidy
+} // namespace clang

clang-tools-extra/clang-tidy/openmp/UseDefaultNoneCheck.h

@@ -0,0 +1,36 @@
+//===--- UseDefaultNoneCheck.h - clang-tidy ---------------------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_OPENMP_USEDEFAULTNONECHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_OPENMP_USEDEFAULTNONECHECK_H
+
+#include "../ClangTidy.h"
+
+namespace clang {
+namespace tidy {
+namespace openmp {
+
+/// Finds OpenMP directives that are allowed to contain a ``default`` clause,
+/// but either don't specify it or the clause is specified but with the kind
+/// other than ``none``, and suggests to use the ``default(none)`` clause.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/openmp-use-default-none.html
+class UseDefaultNoneCheck : public ClangTidyCheck {
+public:
+  UseDefaultNoneCheck(StringRef Name, ClangTidyContext *Context)
+      : ClangTidyCheck(Name, Context) {}
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
+
+} // namespace openmp
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_OPENMP_USEDEFAULTNONECHECK_H

clang-tools-extra/docs/ReleaseNotes.rst

@@ -130,6 +130,13 @@ Improvements to clang-tidy
   <clang-tidy/checks/modernize-use-override>` now supports `OverrideSpelling`
   and `FinalSpelling` options.
 
+- New :doc:`openmp-use-default-none
+  <clang-tidy/checks/openmp-use-default-none>` check.
+
+  Finds OpenMP directives that are allowed to contain a ``default`` clause,
+  but either don't specify it or the clause is specified but with the kind
+  other than ``none``, and suggests to use the ``default(none)`` clause.
+
 Improvements to include-fixer
 -----------------------------
 

clang-tools-extra/docs/clang-tidy/checks/list.rst

@@ -227,6 +227,7 @@ Clang-Tidy Checks
    objc-avoid-spinlock
    objc-forbidden-subclassing
    objc-property-declaration
+   openmp-use-default-none
    performance-faster-string-find
    performance-for-range-copy
    performance-implicit-conversion-in-loop

clang-tools-extra/docs/clang-tidy/checks/openmp-use-default-none.rst

@@ -0,0 +1,53 @@
+.. title:: clang-tidy - openmp-use-default-none
+
+openmp-use-default-none
+=======================
+
+Finds OpenMP directives that are allowed to contain a ``default`` clause,
+but either don't specify it or the clause is specified but with the kind
+other than ``none``, and suggests to use the ``default(none)`` clause.
+
+Using ``default(none)`` clause forces developers to explicitly specify data
+sharing attributes for the variables referenced in the construct,
+thus making it obvious which variables are referenced, and what is their
+data sharing attribute, thus increasing readability and possibly making errors
+easier to spot.
+
+Example
+-------
+
+.. code-block:: c++
+
+  // ``for`` directive can not have ``default`` clause, no diagnostics.
+  void n0(const int a) {
+  #pragma omp for
+    for (int b = 0; b < a; b++)
+      ;
+  }
+
+  // ``parallel`` directive.
+
+  // ``parallel`` directive can have ``default`` clause, but said clause is not
+  // specified, diagnosed.
+  void p0_0() {
+  #pragma omp parallel
+    ;
+    // WARNING: OpenMP directive ``parallel`` does not specify ``default``
+    //          clause. Consider specifying ``default(none)`` clause.
+  }
+
+  // ``parallel`` directive can have ``default`` clause, and said clause is
+  // specified, with ``none`` kind, all good.
+  void p0_1() {
+  #pragma omp parallel default(none)
+    ;
+  }
+
+  // ``parallel`` directive can have ``default`` clause, and said clause is
+  // specified, but with ``shared`` kind, which is not ``none``, diagnose.
+  void p0_2() {
+  #pragma omp parallel default(shared)
+    ;
+    // WARNING: OpenMP directive ``parallel`` specifies ``default(shared)``
+    //          clause. Consider using ``default(none)`` clause instead.
+  }

clang-tools-extra/test/clang-tidy/openmp-use-default-none.cpp

@@ -0,0 +1,160 @@
+// RUN: %check_clang_tidy %s openmp-use-default-none %t -- -- -x c++ -fopenmp=libomp -fopenmp-version=40
+// RUN: %check_clang_tidy %s openmp-use-default-none %t -- -- -x c   -fopenmp=libomp -fopenmp-version=40
+
+//----------------------------------------------------------------------------//
+// Null cases.
+//----------------------------------------------------------------------------//
+
+// 'for' directive can not have 'default' clause, no diagnostics.
+void n0(const int a) {
+#pragma omp for
+  for (int b = 0; b < a; b++)
+    ;
+}
+
+//----------------------------------------------------------------------------//
+// Single-directive positive cases.
+//----------------------------------------------------------------------------//
+
+// 'parallel' directive.
+
+// 'parallel' directive can have 'default' clause, but said clause is not
+// specified, diagnosed.
+void p0_0() {
+#pragma omp parallel
+  ;
+  // CHECK-NOTES: :[[@LINE-2]]:9: warning: OpenMP directive 'parallel' does not specify 'default' clause, consider specifying 'default(none)' clause
+}
+
+// 'parallel' directive can have 'default' clause, and said clause specified,
+// with 'none' kind, all good.
+void p0_1() {
+#pragma omp parallel default(none)
+  ;
+}
+
+// 'parallel' directive can have 'default' clause, and said clause specified,
+// but with 'shared' kind, which is not 'none', diagnose.
+void p0_2() {
+#pragma omp parallel default(shared)
+  ;
+  // CHECK-NOTES: :[[@LINE-2]]:9: warning: OpenMP directive 'parallel' specifies 'default(shared)' clause, consider using 'default(none)' clause instead
+  // CHECK-NOTES: :[[@LINE-3]]:22: note: existing 'default' clause specified here
+}
+
+// 'task' directive.
+
+// 'task' directive can have 'default' clause, but said clause is not
+// specified, diagnosed.
+void p1_0() {
+#pragma omp task
+  ;
+  // CHECK-NOTES: :[[@LINE-2]]:9: warning: OpenMP directive 'task' does not specify 'default' clause, consider specifying 'default(none)' clause
+}
+
+// 'task' directive can have 'default' clause, and said clause specified,
+// with 'none' kind, all good.
+void p1_1() {
+#pragma omp task default(none)
+  ;
+}
+
+// 'task' directive can have 'default' clause, and said clause specified,
+// but with 'shared' kind, which is not 'none', diagnose.
+void p1_2() {
+#pragma omp task default(shared)
+  ;
+  // CHECK-NOTES: :[[@LINE-2]]:9: warning: OpenMP directive 'task' specifies 'default(shared)' clause, consider using 'default(none)' clause instead
+  // CHECK-NOTES: :[[@LINE-3]]:18: note: existing 'default' clause specified here
+}
+
+// 'teams' directive. (has to be inside of 'target' directive)
+
+// 'teams' directive can have 'default' clause, but said clause is not
+// specified, diagnosed.
+void p2_0() {
+#pragma omp target
+#pragma omp teams
+  ;
+  // CHECK-NOTES: :[[@LINE-2]]:9: warning: OpenMP directive 'teams' does not specify 'default' clause, consider specifying 'default(none)' clause
+}
+
+// 'teams' directive can have 'default' clause, and said clause specified,
+// with 'none' kind, all good.
+void p2_1() {
+#pragma omp target
+#pragma omp teams default(none)
+  ;
+}
+
+// 'teams' directive can have 'default' clause, and said clause specified,
+// but with 'shared' kind, which is not 'none', diagnose.
+void p2_2() {
+#pragma omp target
+#pragma omp teams default(shared)
+  ;
+  // CHECK-NOTES: :[[@LINE-2]]:9: warning: OpenMP directive 'teams' specifies 'default(shared)' clause, consider using 'default(none)' clause instead
+  // CHECK-NOTES: :[[@LINE-3]]:19: note: existing 'default' clause specified here
+}
+
+// 'taskloop' directive.
+
+// 'taskloop' directive can have 'default' clause, but said clause is not
+// specified, diagnosed.
+void p3_0(const int a) {
+#pragma omp taskloop
+  for (int b = 0; b < a; b++)
+    ;
+  // CHECK-NOTES: :[[@LINE-3]]:9: warning: OpenMP directive 'taskloop' does not specify 'default' clause, consider specifying 'default(none)' clause
+}
+
+// 'taskloop' directive can have 'default' clause, and said clause specified,
+// with 'none' kind, all good.
+void p3_1(const int a) {
+#pragma omp taskloop default(none) shared(a)
+  for (int b = 0; b < a; b++)
+    ;
+}
+
+// 'taskloop' directive can have 'default' clause, and said clause specified,
+// but with 'shared' kind, which is not 'none', diagnose.
+void p3_2(const int a) {
+#pragma omp taskloop default(shared)
+  for (int b = 0; b < a; b++)
+    ;
+  // CHECK-NOTES: :[[@LINE-3]]:9: warning: OpenMP directive 'taskloop' specifies 'default(shared)' clause, consider using 'default(none)' clause instead
+  // CHECK-NOTES: :[[@LINE-4]]:22: note: existing 'default' clause specified here
+}
+
+//----------------------------------------------------------------------------//
+// Combined directives.
+// Let's not test every single possible permutation/combination of directives,
+// but just *one* combined directive. The rest will be the same.
+//----------------------------------------------------------------------------//
+
+// 'parallel' directive can have 'default' clause, but said clause is not
+// specified, diagnosed.
+void p4_0(const int a) {
+#pragma omp parallel for
+  for (int b = 0; b < a; b++)
+    ;
+  // CHECK-NOTES: :[[@LINE-3]]:9: warning: OpenMP directive 'parallel for' does not specify 'default' clause, consider specifying 'default(none)' clause
+}
+
+// 'parallel' directive can have 'default' clause, and said clause specified,
+// with 'none' kind, all good.
+void p4_1(const int a) {
+#pragma omp parallel for default(none) shared(a)
+  for (int b = 0; b < a; b++)
+    ;
+}
+
+// 'parallel' directive can have 'default' clause, and said clause specified,
+// but with 'shared' kind, which is not 'none', diagnose.
+void p4_2(const int a) {
+#pragma omp parallel for default(shared)
+  for (int b = 0; b < a; b++)
+    ;
+  // CHECK-NOTES: :[[@LINE-3]]:9: warning: OpenMP directive 'parallel for' specifies 'default(shared)' clause, consider using 'default(none)' clause instead
+  // CHECK-NOTES: :[[@LINE-4]]:26: note: existing 'default' clause specified here
+}