Sema: Determine if there're branches from OmpSs-2 region to outside of it

Fixes llvm#20

Author: mikaoP

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -9751,6 +9751,8 @@ def err_oss_shape_incomplete_type : Error<
   "shape of pointer to incomplete type %0">;
 def err_oss_variadic_templates_not_clause_allowed : Error<
   "variadic templates are not allowed in OmpSs-2 clauses">;
+def err_oss_invalid_branch : Error<
+  "invalid branch from OmpSs-2 structured block">;
 def warn_oss_section_is_char : Warning<"array section %select{lower bound|length}0 is of type 'char'">,
   InGroup<CharSubscript>, DefaultIgnore;
 } // end of OmpSs component.

clang/include/clang/Sema/Scope.h

@@ -407,6 +407,11 @@ class Scope {
     return false;
   }
 
+  /// Determines whether this scope is the OmpSs directive scope
+  bool isOmpSsDirectiveScope() const {
+    return (getFlags() & Scope::OmpSsDirectiveScope);
+  }
+
   /// Determines whether this scope is the OpenMP directive scope
   bool isOpenMPDirectiveScope() const {
     return (getFlags() & Scope::OpenMPDirectiveScope);

clang/lib/Sema/SemaStmt.cpp

@@ -3568,6 +3568,17 @@ StmtResult Sema::BuildReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp) {
   if (RetValExp && DiagnoseUnexpandedParameterPack(RetValExp))
     return StmtError();
 
+  // OmpSs directives introduce a new Scope that is both
+  // a FnScope and OmpSsDirectiveScope.
+  // Lambdas are FnScopes too, so we can determine if
+  // the stmt belongs to the lambda or the OmpSs-2 region.
+  if (getLangOpts().OmpSs
+      && getCurScope()->getFnParent()->isOmpSsDirectiveScope()) {
+
+    Diag(ReturnLoc, diag::err_oss_invalid_branch);
+    return StmtError();
+  }
+
   if (isa<CapturingScopeInfo>(getCurFunction()))
     return ActOnCapScopeReturnStmt(ReturnLoc, RetValExp);
 

clang/test/OmpSs/Sema/task_body_return.cpp

@@ -0,0 +1,32 @@
+// RUN: %clang_cc1 -verify -x c++ -std=c++11 -fompss-2 -ferror-limit 100 -o - %s
+
+void bar() {
+  #pragma oss task
+  {
+    auto l = []() {
+        return 1;
+        break; // expected-error {{'break' statement not in loop or switch statement}}
+        goto label; // expected-error {{use of undeclared label 'label'}}
+    };
+label:
+    return; // expected-error {{invalid branch from OmpSs-2 structured block}}
+    break; // expected-error {{'break' statement not in loop or switch statement}}
+    goto label;
+  }
+  auto l = []() {
+    #pragma oss task
+    {
+      for (int i = 0; i < 10; ++i)
+      #pragma oss task
+      {
+        continue; // expected-error {{'continue' statement not in loop statement}}
+        return 2; // expected-error {{invalid branch from OmpSs-2 structured block}}
+      }
+      return 3; // expected-error {{invalid branch from OmpSs-2 structured block}}
+      break; // expected-error {{'break' statement not in loop or switch statement}}
+      goto label; // expected-error {{use of undeclared label 'label'}}
+    }
+label:
+    return 4;
+  };
+}