[Openmp-commits] [PATCH] D57585: [AST][OpenMP] OpenMP Sections / Section constructs contain Structured blocks

[Roman Lebedev via Phabricator via Openmp-commits]

lebedev.ri created this revision.
lebedev.ri added reviewers: ABataev, OpenMP.
lebedev.ri added projects: clang, OpenMP.
Herald added subscribers: openmp-commits, guansong.

I'm working on a clang-tidy check, much like existing bugprone-exception-escape <http://clang.llvm.org/extra/clang-tidy/checks/bugprone-exception-escape.html>,
to detect when an exception might escape out of an OpenMP construct it isn't supposed to escape from.
For that i will be using the `nothrow` bit of `CapturedDecl`s.

While that bit is already correctly set for some constructs, e.g. `#pragma omp parallel`: https://godbolt.org/z/2La7pv
it isn't set for the `#pragma omp sections`, or `#pragma omp section`: https://godbolt.org/z/qZ-EbP

If i'm reading `OpenMP Application Programming Interface Version 5.0 November 2018` <https://www.openmp.org/wp-content/uploads/OpenMP-API-Specification-5.0.pdf> correctly,
they should be, as per `2.8.1 sections Construct`, starting with page 86:

- The sections construct is a non-iterative worksharing construct that contains a set of **structured blocks** that are to be distributed among and executed by the threads in a team. Each **structured block** is executed once by one of the threads in the team in the context of its implicit task.
- The syntax of the sections construct is as follows: #pragma omp sections [clause[ [,] clause] ... ] new-line { [#pragma omp section new-line] **structured-block** ...
- Description Each **structured block** in the sections construct is preceded by a section directive except possibly **the first block**, for which a preceding section directive is optional.

- Restrictions • The code enclosed in a sections construct must be a **structured block**.
  - A throw executed inside a sections region must cause execution to resume within the same section of the sections region, and the same thread that threw the exception must catch it.


Repository:
  rC Clang

https://reviews.llvm.org/D57585

Files:
  lib/Sema/SemaOpenMP.cpp
  test/AST/ast-dump-openmp-sections.cpp


Index: test/AST/ast-dump-openmp-sections.cpp
===================================================================
--- /dev/null
+++ test/AST/ast-dump-openmp-sections.cpp
@@ -0,0 +1,57 @@
+// RUN: %clang_cc1 -verify -fopenmp -ast-dump %s | FileCheck %s
+// RUN: %clang_cc1 -verify -fopenmp-simd -ast-dump %s | FileCheck %s
+// expected-no-diagnostics
+
+void sections() {
+#pragma omp sections
+  {
+#pragma omp section
+    {
+    }
+#pragma omp section
+    {
+    }
+  }
+}
+
+// CHECK: `-FunctionDecl
+// CHECK-NEXT:   `-CompoundStmt
+// CHECK-NEXT:     `-OMPSectionsDirective
+// CHECK-NEXT:       `-CapturedStmt
+// CHECK-NEXT:         `-CapturedDecl {{.*}} nothrow
+// CHECK-NEXT:           |-CompoundStmt
+// CHECK-NEXT:           | |-OMPSectionDirective
+// CHECK-NEXT:           | | `-CapturedStmt
+// CHECK-NEXT:           | |   `-CapturedDecl {{.*}} nothrow
+// CHECK-NEXT:           | |     |-CompoundStmt
+// CHECK-NEXT:           | |     `-ImplicitParamDecl
+// CHECK-NEXT:           | `-OMPSectionDirective
+// CHECK-NEXT:           |   `-CapturedStmt
+// CHECK-NEXT:           |     `-CapturedDecl {{.*}} nothrow
+// CHECK-NEXT:           |       |-CompoundStmt
+// CHECK-NEXT:           |       `-ImplicitParamDecl
+// CHECK-NEXT:           |-ImplicitParamDecl
+// CHECK-NEXT:           |-CXXRecordDecl
+// CHECK-NEXT:           | |-DefinitionData
+// CHECK-NEXT:           | | |-DefaultConstructor
+// CHECK-NEXT:           | | |-CopyConstructor
+// CHECK-NEXT:           | | |-MoveConstructor
+// CHECK-NEXT:           | | |-CopyAssignment
+// CHECK-NEXT:           | | |-MoveAssignment
+// CHECK-NEXT:           | | `-Destructor
+// CHECK-NEXT:           | `-CapturedRecordAttr
+// CHECK-NEXT:           |-CapturedDecl {{.*}} nothrow
+// CHECK-NEXT:           | |-CompoundStmt
+// CHECK-NEXT:           | `-ImplicitParamDecl
+// CHECK-NEXT:           |-CXXRecordDecl
+// CHECK-NEXT:           | |-DefinitionData
+// CHECK-NEXT:           | | |-DefaultConstructor
+// CHECK-NEXT:           | | |-CopyConstructor
+// CHECK-NEXT:           | | |-MoveConstructor
+// CHECK-NEXT:           | | |-CopyAssignment
+// CHECK-NEXT:           | | |-MoveAssignment
+// CHECK-NEXT:           | | `-Destructor
+// CHECK-NEXT:           | `-CapturedRecordAttr
+// CHECK-NEXT:           `-CapturedDecl {{.*}} nothrow
+// CHECK-NEXT:             |-CompoundStmt
+// CHECK-NEXT:             `-ImplicitParamDecl
Index: lib/Sema/SemaOpenMP.cpp
===================================================================
--- lib/Sema/SemaOpenMP.cpp
+++ lib/Sema/SemaOpenMP.cpp
@@ -5969,6 +5969,13 @@
     return StmtError();
   }
 
+  // 1.2.2 OpenMP Language Terminology
+  // Structured block - An executable statement with a single entry at the
+  // top and a single exit at the bottom.
+  // The point of exit cannot be a branch out of the structured block.
+  // longjmp() and throw() must not violate the entry/exit criteria.
+  cast<CapturedStmt>(AStmt)->getCapturedDecl()->setNothrow();
+
   setFunctionHasBranchProtectedScope();
 
   return OMPSectionsDirective::Create(Context, StartLoc, EndLoc, Clauses, AStmt,
@@ -5983,6 +5990,13 @@
 
   assert(isa<CapturedStmt>(AStmt) && "Captured statement expected");
 
+  // 1.2.2 OpenMP Language Terminology
+  // Structured block - An executable statement with a single entry at the
+  // top and a single exit at the bottom.
+  // The point of exit cannot be a branch out of the structured block.
+  // longjmp() and throw() must not violate the entry/exit criteria.
+  cast<CapturedStmt>(AStmt)->getCapturedDecl()->setNothrow();
+
   setFunctionHasBranchProtectedScope();
   DSAStack->setParentCancelRegion(DSAStack->isCancelRegion());
 


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