[clang][OpenMP] In 6.0, can omit length in array section (llvm#148048)

In OpenMP 6.0 specification, section 5.2.5 Array Sections, page 166,
lines 28-28:

When the length is absent and the size of the dimension is not known,
the array section is an assumed-size array.

Testing
- Updated LIT test
- check-all
- OpenMP_VV (formerly sollve) test case
tests/6.0/target/test_target_assumed_array_size.c

Author: ddpagan

clang/docs/OpenMPSupport.rst

@@ -443,7 +443,7 @@ implementation.
 +-------------------------------------------------------------+---------------------------+---------------------------+--------------------------------------------------------------------------+
 | Traits for default device envirable                         | :none:`unclaimed`         | :none:`unclaimed`         |                                                                          |
 +-------------------------------------------------------------+---------------------------+---------------------------+--------------------------------------------------------------------------+
-| Optionally omit array length expression                     | :none:`unclaimed`         | :none:`unclaimed`         |                                                                          |
+| Optionally omit array length expression                     | :good:`done`              | :none:`unclaimed`         | https://github.com/llvm/llvm-project/pull/148048                         |
 +-------------------------------------------------------------+---------------------------+---------------------------+--------------------------------------------------------------------------+
 | Canonical loop sequences                                    | :none:`unclaimed`         | :none:`unclaimed`         |                                                                          |
 +-------------------------------------------------------------+---------------------------+---------------------------+--------------------------------------------------------------------------+

clang/docs/ReleaseNotes.rst

@@ -1316,6 +1316,7 @@ OpenMP Support
 - Deprecation warning has been emitted for deprecated delimited form of ``declare target``.
 - Added parsing and semantic analysis support for the 'need_device_addr' 
   modifier in the 'adjust_args' clause.
+- Allow array length to be omitted in array section subscript expression.
 
 Improvements
 ^^^^^^^^^^^^

clang/lib/Sema/SemaOpenMP.cpp

@@ -24392,7 +24392,7 @@ ExprResult SemaOpenMP::ActOnOMPArraySectionExpr(
         return ExprError();
       }
     }
-  } else if (ColonLocFirst.isValid() &&
+  } else if (SemaRef.getLangOpts().OpenMP < 60 && ColonLocFirst.isValid() &&
              (OriginalTy.isNull() || (!OriginalTy->isConstantArrayType() &&
                                       !OriginalTy->isVariableArrayType()))) {
     // OpenMP 5.0, [2.1.5 Array Sections]