[OpenMP] Generate better diagnostics for cancel and cancellation point

checkNestingOfRegions uses CancelRegion to determine whether cancel and
cancellation point are valid in the given nesting. This leads to unuseful
diagnostics if CancelRegion is invalid. The given test case has produced:
  region cannot be closely nested inside 'parallel' region

As a solution, introduce checkCancelRegion and call it first to get the
expected error:
  one of 'for', 'parallel', 'sections' or 'taskgroup' is expected

Differential Revision: https://reviews.llvm.org/D30135

llvm-svn: 295808

3 files changed, 36 insertions, 14 deletions

diff --git a/clang/lib/Sema/SemaOpenMP.cpp b/clang/lib/Sema/SemaOpenMP.cpp
index 87115054b0c..7d479974550 100644
--- a/clang/lib/Sema/SemaOpenMP.cpp
+++ b/clang/lib/Sema/SemaOpenMP.cpp
@@ -1956,7 +1956,23 @@ StmtResult Sema::ActOnOpenMPRegionEnd(StmtResult S,
   return SR;
 }
 
-static bool CheckNestingOfRegions(Sema &SemaRef, DSAStackTy *Stack,
+static bool checkCancelRegion(Sema &SemaRef, OpenMPDirectiveKind CurrentRegion,
+                              OpenMPDirectiveKind CancelRegion,
+                              SourceLocation StartLoc) {
+  // CancelRegion is only needed for cancel and cancellation_point.
+  if (CurrentRegion != OMPD_cancel && CurrentRegion != OMPD_cancellation_point)
+    return false;
+
+  if (CancelRegion == OMPD_parallel || CancelRegion == OMPD_for ||
+      CancelRegion == OMPD_sections || CancelRegion == OMPD_taskgroup)
+    return false;
+
+  SemaRef.Diag(StartLoc, diag::err_omp_wrong_cancel_region)
+      << getOpenMPDirectiveName(CancelRegion);
+  return true;
+}
+
+static bool checkNestingOfRegions(Sema &SemaRef, DSAStackTy *Stack,
                                   OpenMPDirectiveKind CurrentRegion,
                                   const DeclarationNameInfo &CurrentName,
                                   OpenMPDirectiveKind CancelRegion,
@@ -2256,7 +2272,9 @@ StmtResult Sema::ActOnOpenMPExecutableDirective(
     OpenMPDirectiveKind CancelRegion, ArrayRef<OMPClause *> Clauses,
     Stmt *AStmt, SourceLocation StartLoc, SourceLocation EndLoc) {
   StmtResult Res = StmtError();
-  if (CheckNestingOfRegions(*this, DSAStack, Kind, DirName, CancelRegion,
+  // First check CancelRegion which is then used in checkNestingOfRegions.
+  if (checkCancelRegion(*this, Kind, CancelRegion, StartLoc) ||
+      checkNestingOfRegions(*this, DSAStack, Kind, DirName, CancelRegion,
                             StartLoc))
     return StmtError();
 
@@ -5860,12 +5878,6 @@ StmtResult
 Sema::ActOnOpenMPCancellationPointDirective(SourceLocation StartLoc,
                                             SourceLocation EndLoc,
                                             OpenMPDirectiveKind CancelRegion) {
-  if (CancelRegion != OMPD_parallel && CancelRegion != OMPD_for &&
-      CancelRegion != OMPD_sections && CancelRegion != OMPD_taskgroup) {
-    Diag(StartLoc, diag::err_omp_wrong_cancel_region)
-        << getOpenMPDirectiveName(CancelRegion);
-    return StmtError();
-  }
   if (DSAStack->isParentNowaitRegion()) {
     Diag(StartLoc, diag::err_omp_parent_cancel_region_nowait) << 0;
     return StmtError();
@@ -5882,12 +5894,6 @@ StmtResult Sema::ActOnOpenMPCancelDirective(ArrayRef<OMPClause *> Clauses,
                                             SourceLocation StartLoc,
                                             SourceLocation EndLoc,
                                             OpenMPDirectiveKind CancelRegion) {
-  if (CancelRegion != OMPD_parallel && CancelRegion != OMPD_for &&
-      CancelRegion != OMPD_sections && CancelRegion != OMPD_taskgroup) {
-    Diag(StartLoc, diag::err_omp_wrong_cancel_region)
-        << getOpenMPDirectiveName(CancelRegion);
-    return StmtError();
-  }
   if (DSAStack->isParentNowaitRegion()) {
     Diag(StartLoc, diag::err_omp_parent_cancel_region_nowait) << 1;
     return StmtError();
diff --git a/clang/test/OpenMP/cancel_messages.cpp b/clang/test/OpenMP/cancel_messages.cpp
index e23b5c337bc..f8bbe2c36be 100644
--- a/clang/test/OpenMP/cancel_messages.cpp
+++ b/clang/test/OpenMP/cancel_messages.cpp
@@ -4,8 +4,16 @@ int main(int argc, char **argv) {
 #pragma omp cancellation       // expected-error {{expected an OpenMP directive}}
 #pragma omp cancel // expected-error {{one of 'for', 'parallel', 'sections' or 'taskgroup' is expected}}
   ;
+#pragma omp parallel
+  {
+#pragma omp cancel // expected-error {{one of 'for', 'parallel', 'sections' or 'taskgroup' is expected}}
+  }
 #pragma omp cancel parallel untied // expected-error {{unexpected OpenMP clause 'untied' in directive '#pragma omp cancel'}}
 #pragma omp cancel unknown         // expected-error {{one of 'for', 'parallel', 'sections' or 'taskgroup' is expected}}
+#pragma omp parallel
+  {
+#pragma omp cancel unknown         // expected-error {{one of 'for', 'parallel', 'sections' or 'taskgroup' is expected}}
+  }
 #pragma omp cancel sections(       // expected-warning {{extra tokens at the end of '#pragma omp cancel' are ignored}}
 #pragma omp cancel for, )          // expected-warning {{extra tokens at the end of '#pragma omp cancel' are ignored}}
 #pragma omp cancel taskgroup()     // expected-warning {{extra tokens at the end of '#pragma omp cancel' are ignored}}
diff --git a/clang/test/OpenMP/cancellation_point_messages.cpp b/clang/test/OpenMP/cancellation_point_messages.cpp
index 2324915e83f..21b0e9c2fa2 100644
--- a/clang/test/OpenMP/cancellation_point_messages.cpp
+++ b/clang/test/OpenMP/cancellation_point_messages.cpp
@@ -4,8 +4,16 @@ int main(int argc, char **argv) {
 #pragma omp cancellation       // expected-error {{expected an OpenMP directive}}
 #pragma omp cancellation point // expected-error {{one of 'for', 'parallel', 'sections' or 'taskgroup' is expected}}
   ;
+#pragma omp parallel
+  {
+#pragma omp cancellation point // expected-error {{one of 'for', 'parallel', 'sections' or 'taskgroup' is expected}}
+  }
 #pragma omp cancellation point parallel untied // expected-error {{unexpected OpenMP clause 'untied' in directive '#pragma omp cancellation point'}}
 #pragma omp cancellation point unknown         // expected-error {{one of 'for', 'parallel', 'sections' or 'taskgroup' is expected}}
+#pragma omp parallel
+  {
+#pragma omp cancellation point unknown         // expected-error {{one of 'for', 'parallel', 'sections' or 'taskgroup' is expected}}
+  }
 #pragma omp cancellation point sections(       // expected-warning {{extra tokens at the end of '#pragma omp cancellation point' are ignored}}
 #pragma omp cancellation point for, )          // expected-warning {{extra tokens at the end of '#pragma omp cancellation point' are ignored}}
 #pragma omp cancellation point taskgroup()     // expected-warning {{extra tokens at the end of '#pragma omp cancellation point' are ignored}}