[OPENMP] Info about OpenMP Support in Users Manual, NFC.

Differential Revision: http://reviews.llvm.org/D12152


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@245823 91177308-0d34-0410-b5e6-96231b3b80d8

docs/UsersManual.rst

@@ -1852,6 +1852,32 @@ Objective-C Language Features
 Objective-C++ Language Features
 ===============================
 
+.. _openmp:
+
+OpenMP Features
+===============
+
+Clang supports all OpenMP 3.1 directives and clauses.  In addition, some
+features of OpenMP 4.0 are supported.  For example, ``#pragma omp simd``,
+``#pragma omp for simd``, ``#pragma omp parallel for simd`` directives, extended
+set of atomic constructs, ``proc_bind`` clause for all parallel-based
+directives, ``depend`` clause for ``#pragma omp task`` directive (except for
+array sections), ``#pragma omp cancel`` and ``#pragma omp cancellation point``
+directives, and ``#pragma omp taskgroup`` directive.
+
+OpenMP support is disabled by default. Use :option:`-fopenmp=libomp` to enable
+it. Support for OpenMP can be disabled with :option:`-fno-openmp`.
+
+Controlling implementation limits
+---------------------------------
+
+.. option:: -fopenmp-use-tls
+
+ Controls code generation for OpenMP threadprivate variables. In presence of
+ this option all threadprivate variables are generated the same way as thread
+ local variables, using TLS support. If :option:`-fno-openmp-use-tls`
+ is provided or target does not support TLS, code generation for threadprivate
+ variables relies on OpenMP runtime library.
 
 .. _target_features: