[OpenMP] Prevent nesting of target constructs within target code execution regions.

Summary:
This patch enhances Sema to check for the following restriction:

OpenMP 4.5 [2.17 Nesting of Regions]
If a target, target update, target data, target enter data, or
target exit data construct is encountered during execution of a
target region, the behavior is unspecified.

Reviewers: ABataev

Differential Revision: http://reviews.llvm.org/D16758

llvm-svn: 259366

1 files changed, 1 insertions, 0 deletions

diff --git a/clang/test/OpenMP/target_messages.cpp b/clang/test/OpenMP/target_messages.cpp
index 86a91838ce0..361da5f3819 100644
--- a/clang/test/OpenMP/target_messages.cpp
+++ b/clang/test/OpenMP/target_messages.cpp
@@ -21,6 +21,7 @@ int main(int argc, char **argv) {
   #pragma omp target } // expected-warning {{extra tokens at the end of '#pragma omp target' are ignored}}
   foo();
   #pragma omp target
+  foo();
   // expected-warning@+1 {{extra tokens at the end of '#pragma omp target' are ignored}}
   #pragma omp target unknown()
   foo();