[gcc r12-2992] Fortran: Add OpenMP's nothing directive support

[gcc r12-2992] Fortran: Add OpenMP's nothing directive support

[Tobias Burnus]

https://gcc.gnu.org/g:f74433e70ae94a3b5291e45fea488b1cfdee4a34

commit r12-2992-gf74433e70ae94a3b5291e45fea488b1cfdee4a34
Author: Tobias Burnus <tobias@codesourcery.com>
Date:   Wed Aug 18 15:21:18 2021 +0200

    Fortran: Add OpenMP's nothing directive support
    
    Fortran version of commit 5079b7781a2c506dcdfb241347d74c7891268225
    
    gcc/fortran/ChangeLog:
    
            * match.h (gfc_match_omp_nothing): New.
            * openmp.c (gfc_match_omp_nothing): New.
            * parse.c (decode_omp_directive): Match 'nothing' directive.
    
    gcc/testsuite/ChangeLog:
    
            * gfortran.dg/nothing-1.f90: New test.
            * gfortran.dg/nothing-2.f90: New test.

Diff:
---
 gcc/fortran/match.h                     |  1 +
 gcc/fortran/openmp.c                    | 11 +++++++++++
 gcc/fortran/parse.c                     |  3 +++
 gcc/testsuite/gfortran.dg/nothing-1.f90 | 28 ++++++++++++++++++++++++++++
 gcc/testsuite/gfortran.dg/nothing-2.f90 |  7 +++++++
 5 files changed, 50 insertions(+)

diff --git a/gcc/fortran/match.h b/gcc/fortran/match.h
index aac16a8d3d0..5127b4b8ea3 100644
--- a/gcc/fortran/match.h
+++ b/gcc/fortran/match.h
@@ -175,6 +175,7 @@ match gfc_match_omp_masked_taskloop_simd (void);
 match gfc_match_omp_master (void);
 match gfc_match_omp_master_taskloop (void);
 match gfc_match_omp_master_taskloop_simd (void);
+match gfc_match_omp_nothing (void);
 match gfc_match_omp_ordered (void);
 match gfc_match_omp_ordered_depend (void);
 match gfc_match_omp_parallel (void);
diff --git a/gcc/fortran/openmp.c b/gcc/fortran/openmp.c
index 9675b658409..fd219dc9c4d 100644
--- a/gcc/fortran/openmp.c
+++ b/gcc/fortran/openmp.c
@@ -4797,6 +4797,17 @@ gfc_match_omp_ordered (void)
   return match_omp (EXEC_OMP_ORDERED, OMP_ORDERED_CLAUSES);
 }
 
+match
+gfc_match_omp_nothing (void)
+{
+  if (gfc_match_omp_eos () != MATCH_YES)
+    {
+      gfc_error ("Unexpected junk after $OMP NOTHING statement at %C");
+      return MATCH_ERROR;
+    }
+  /* Will use ST_NONE; therefore, no EXEC_OMP_ is needed.  */
+  return MATCH_YES;
+}
 
 match
 gfc_match_omp_ordered_depend (void)
diff --git a/gcc/fortran/parse.c b/gcc/fortran/parse.c
index 24cc9bfb9f1..d004732677c 100644
--- a/gcc/fortran/parse.c
+++ b/gcc/fortran/parse.c
@@ -1005,6 +1005,9 @@ decode_omp_directive (void)
 	      ST_OMP_MASTER_TASKLOOP);
       matcho ("master", gfc_match_omp_master, ST_OMP_MASTER);
       break;
+    case 'n':
+      matcho ("nothing", gfc_match_omp_nothing, ST_NONE);
+      break;
     case 'l':
       matcho ("loop", gfc_match_omp_loop, ST_OMP_LOOP);
       break;
diff --git a/gcc/testsuite/gfortran.dg/nothing-1.f90 b/gcc/testsuite/gfortran.dg/nothing-1.f90
new file mode 100644
index 00000000000..9fc24d4bd6c
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/nothing-1.f90
@@ -0,0 +1,28 @@
+module m
+  implicit none (type, external)
+  !$omp nothing
+
+  type t
+    !$omp nothing
+    integer s
+  end type
+
+contains
+
+integer function foo (i)
+  integer :: i
+
+  !$omp nothing
+  if (.false.) &
+& &    !$omp nothing
+    i = i + 1
+
+! In the following, '& & !$' is not a valid OpenMP sentinel and,
+! hence, the line is regarded as comment
+  if (.false.) &
+&   & !$omp nothing
+    then
+  end if
+  foo = i
+end
+end module
diff --git a/gcc/testsuite/gfortran.dg/nothing-2.f90 b/gcc/testsuite/gfortran.dg/nothing-2.f90
new file mode 100644
index 00000000000..74a4a5a22b0
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/nothing-2.f90
@@ -0,0 +1,7 @@
+pure subroutine foo
+  !$omp nothing  ! { dg-error "OpenMP directives other than SIMD or DECLARE TARGET at .1. may not appear in PURE procedures" }
+end subroutine
+
+subroutine bar
+  !$omp nothing foo  ! { dg-error "Unexpected junk after $OMP NOTHING statement" }
+end