[OpenMP] [Docs] Update comand line docs and link it from top-level md file.

Change-Id: I40a79307cff7734ffeafe95fe5906eba18594b4b
(cherry picked from commit 2cf6b8f)

Author: dhruvachak

openmp/docs/CommandLineArgumentReference.rst

@@ -184,3 +184,23 @@ Do not link the device library for CUDA or HIP device compilation.
 ^^^^^^^^^^^^^
 Do not include the default CUDA or HIP headers, and do not add CUDA or HIP
 include paths.
+
+``-fopenmp-target-fast,  -fno-openmp-target-fast``
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Enables fast optimization options for OpenMP target offloading:
+-fopenmp-target-ignore-env-vars, -fopenmp-assume-no-thread-state,
+-fopenmp-assume-no-nested-parallelism. Enables -O3 if no -O* level is
+specified.
+
+``-fopenmp-target-ignore-env-vars, -fno-openmp-target-ignore-env-vars``
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Generate code assuming that device related environment variables can be ignored.
+
+``-fopenmp-assume-no-thread-state, -fno-openmp-assume-no-thread-state``
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Assume that no thread in a parallel region will modify an ICV.
+
+``-fopenmp-assume-no-nested-parallelism, -fno-openmp-assume-no-nested-parallelism``
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Assume that no thread in a parallel region will encounter a parallel region.
+

openmp/docs/openmp.md

@@ -78,7 +78,7 @@ Obtain the value of `gpu-arch` by running the following command:
 [//]: # (dated link below, needs updating)
 
 See the complete list of compiler command-line references
-[here](https://github.com/ROCm/llvm-project/blob/amd-stg-open/clang/docs/CommandGuide/clang.rst).
+[here](https://github.com/ROCm/llvm-project/blob/amd-staging/openmp/docs/CommandLineArgumentReference.rst).
 
 ### Using `rocprof` with OpenMP