Add OpenACC 2.6 `serial' construct support

    The `serial' construct (cf. section 2.5.3 of the OpenACC 2.6 standard)
    is equivalent to a `parallel' construct with clauses `num_gangs(1)
    num_workers(1) vector_length(1)' implied.
    These clauses are therefore not supported with the `serial'
    construct. All the remaining clauses accepted with `parallel' are also
    accepted with `serial'.

    The `serial' construct is implemented like `parallel', except for
    hardcoding dimensions rather than taking them from the relevant
    clauses, in `expand_omp_target'.

    Separate codes are used to denote the `serial' construct throughout the
    middle end, even though the mapping of `serial' to an equivalent
    `parallel' construct could have been done in the individual language
    frontends. In particular, this allows to distinguish between compute
    constructs in warnings, error messages, dumps etc.

    2019-11-12  Maciej W. Rozycki  <macro@codesourcery.com>
                Tobias Burnus  <tobias@codesourcery.com>
                Frederik Harwath  <frederik@codesourcery.com>
                Thomas Schwinge  <thomas@codesourcery.com>

    gcc/
    * gimple.h (gf_mask): Add GF_OMP_TARGET_KIND_OACC_SERIAL
    enumeration constant.
    (is_gimple_omp_oacc): Handle GF_OMP_TARGET_KIND_OACC_SERIAL.
    (is_gimple_omp_offloaded): Likewise.
    * gimplify.c (omp_region_type): Add ORT_ACC_SERIAL enumeration
    constant.  Adjust the value of ORT_NONE accordingly.
    (is_gimple_stmt): Handle OACC_SERIAL.
    (oacc_default_clause): Handle ORT_ACC_SERIAL.
    (gomp_needs_data_present): Likewise.
    (gimplify_adjust_omp_clauses): Likewise.
    (gimplify_omp_workshare): Handle OACC_SERIAL.
    (gimplify_expr): Likewise.
    * omp-expand.c (expand_omp_target):
    Handle GF_OMP_TARGET_KIND_OACC_SERIAL.
    (build_omp_regions_1, omp_make_gimple_edges): Likewise.
    * omp-low.c (is_oacc_parallel): Rename function to...
    (is_oacc_parallel_or_serial): ... this.
    Handle GF_OMP_TARGET_KIND_OACC_SERIAL.
    (scan_sharing_clauses): Adjust accordingly.
    (scan_omp_for): Likewise.
    (lower_oacc_head_mark): Likewise.
    (convert_from_firstprivate_int): Likewise.
    (lower_omp_target): Likewise.
    (check_omp_nesting_restrictions): Handle
    GF_OMP_TARGET_KIND_OACC_SERIAL.
    (lower_oacc_reductions): Likewise.
    (lower_omp_target): Likewise.
    * tree.def (OACC_SERIAL): New tree code.
    * tree-pretty-print.c (dump_generic_node): Handle OACC_SERIAL.

    * doc/generic.texi (OpenACC): Document OACC_SERIAL.

    gcc/c-family/
    * c-pragma.h (pragma_kind): Add PRAGMA_OACC_SERIAL enumeration
    constant.
    * c-pragma.c (oacc_pragmas): Add "serial" entry.

    gcc/c/
    * c-parser.c (OACC_SERIAL_CLAUSE_MASK): New macro.
    (c_parser_oacc_kernels_parallel): Rename function to...
    (c_parser_oacc_compute): ... this.  Handle PRAGMA_OACC_SERIAL.
    (c_parser_omp_construct): Update accordingly.

    gcc/cp/
    * constexpr.c (potential_constant_expression_1): Handle
    OACC_SERIAL.
    * parser.c (OACC_SERIAL_CLAUSE_MASK): New macro.
    (cp_parser_oacc_kernels_parallel): Rename function to...
    (cp_parser_oacc_compute): ... this.  Handle PRAGMA_OACC_SERIAL.
    (cp_parser_omp_construct): Update accordingly.
    (cp_parser_pragma): Handle PRAGMA_OACC_SERIAL.  Fix alphabetic
    order.
    * pt.c (tsubst_expr): Handle OACC_SERIAL.

    gcc/fortran/
    * gfortran.h (gfc_statement): Add ST_OACC_SERIAL_LOOP,
    ST_OACC_END_SERIAL_LOOP, ST_OACC_SERIAL and ST_OACC_END_SERIAL
    enumeration constants.
    (gfc_exec_op): Add EXEC_OACC_SERIAL_LOOP and EXEC_OACC_SERIAL
    enumeration constants.
    * match.h (gfc_match_oacc_serial): New prototype.
    (gfc_match_oacc_serial_loop): Likewise.
    * dump-parse-tree.c (show_omp_node, show_code_node): Handle
    EXEC_OACC_SERIAL_LOOP and EXEC_OACC_SERIAL.
    * match.c (match_exit_cycle): Handle EXEC_OACC_SERIAL_LOOP.
    * openmp.c (OACC_SERIAL_CLAUSES): New macro.
    (gfc_match_oacc_serial_loop): New function.
    (gfc_match_oacc_serial): Likewise.
    (oacc_is_loop): Handle EXEC_OACC_SERIAL_LOOP.
    (resolve_omp_clauses): Handle EXEC_OACC_SERIAL.
    (oacc_code_to_statement): Handle EXEC_OACC_SERIAL and
    EXEC_OACC_SERIAL_LOOP.
    (gfc_resolve_oacc_directive): Likewise.
    * parse.c (decode_oacc_directive) <'s'>: Add case for "serial"
    and "serial loop".
    (next_statement): Handle ST_OACC_SERIAL_LOOP and ST_OACC_SERIAL.
    (gfc_ascii_statement): Likewise.  Handle ST_OACC_END_SERIAL_LOOP
    and ST_OACC_END_SERIAL.
    (parse_oacc_structured_block): Handle ST_OACC_SERIAL.
    (parse_oacc_loop): Handle ST_OACC_SERIAL_LOOP and
    ST_OACC_END_SERIAL_LOOP.
    (parse_executable): Handle ST_OACC_SERIAL_LOOP and
    ST_OACC_SERIAL.
    (is_oacc): Handle EXEC_OACC_SERIAL_LOOP and EXEC_OACC_SERIAL.
    * resolve.c (gfc_resolve_blocks, gfc_resolve_code): Likewise.
    * st.c (gfc_free_statement): Likewise.
    * trans-openmp.c (gfc_trans_oacc_construct): Handle
    EXEC_OACC_SERIAL.
    (gfc_trans_oacc_combined_directive): Handle
    EXEC_OACC_SERIAL_LOOP.
    (gfc_trans_oacc_directive): Handle EXEC_OACC_SERIAL_LOOP and
    EXEC_OACC_SERIAL.
    * trans.c (trans_code): Likewise.

    gcc/testsuite/
    * c-c++-common/goacc/parallel-dims.c: New test.
    * gfortran.dg/goacc/parallel-dims.f90: New test.

    libgomp/
    * testsuite/libgomp.oacc-c-c++-common/parallel-dims.c: New test.
    * testsuite/libgomp.oacc-fortran/parallel-dims-aux.c: New test.
    * testsuite/libgomp.oacc-fortran/parallel-dims.f89: New test.
    * testsuite/libgomp.oacc-fortran/parallel-dims-2.f90: New test.

Reviewed-by: Thomas Schwinge <thomas@codesourcery.com>


Co-Authored-By: Frederik Harwath <frederik@codesourcery.com>
Co-Authored-By: Thomas Schwinge <thomas@codesourcery.com>
Co-Authored-By: Tobias Burnus <tobias@codesourcery.com>

From-SVN: r278082

11 files changed, 146 insertions, 13 deletions

diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog
index 0f14ad1..d92a6ad 100644
--- a/gcc/fortran/ChangeLog
+++ b/gcc/fortran/ChangeLog
@@ -1,3 +1,46 @@
+2019-11-12  Maciej W. Rozycki  <macro@codesourcery.com>
+	    Frederik Harwath  <frederik@codesourcery.com>
+
+	gcc/fortran/
+	* gfortran.h (gfc_statement): Add ST_OACC_SERIAL_LOOP,
+	ST_OACC_END_SERIAL_LOOP, ST_OACC_SERIAL and ST_OACC_END_SERIAL
+	enumeration constants.
+	(gfc_exec_op): Add EXEC_OACC_SERIAL_LOOP and EXEC_OACC_SERIAL
+	enumeration constants.
+	* match.h (gfc_match_oacc_serial): New prototype.
+	(gfc_match_oacc_serial_loop): Likewise.
+	* dump-parse-tree.c (show_omp_node, show_code_node): Handle
+	EXEC_OACC_SERIAL_LOOP and EXEC_OACC_SERIAL.
+	* match.c (match_exit_cycle): Handle EXEC_OACC_SERIAL_LOOP.
+	* openmp.c (OACC_SERIAL_CLAUSES): New macro.
+	(gfc_match_oacc_serial_loop): New function.
+	(gfc_match_oacc_serial): Likewise.
+	(oacc_is_loop): Handle EXEC_OACC_SERIAL_LOOP.
+	(resolve_omp_clauses): Handle EXEC_OACC_SERIAL.
+	(oacc_code_to_statement): Handle EXEC_OACC_SERIAL and
+	EXEC_OACC_SERIAL_LOOP.
+	(gfc_resolve_oacc_directive): Likewise.
+	* parse.c (decode_oacc_directive) <'s'>: Add case for "serial"
+	and "serial loop".
+	(next_statement): Handle ST_OACC_SERIAL_LOOP and ST_OACC_SERIAL.
+	(gfc_ascii_statement): Likewise.  Handle ST_OACC_END_SERIAL_LOOP
+	and ST_OACC_END_SERIAL.
+	(parse_oacc_structured_block): Handle ST_OACC_SERIAL.
+	(parse_oacc_loop): Handle ST_OACC_SERIAL_LOOP and
+	ST_OACC_END_SERIAL_LOOP.
+	(parse_executable): Handle ST_OACC_SERIAL_LOOP and
+	ST_OACC_SERIAL.
+	(is_oacc): Handle EXEC_OACC_SERIAL_LOOP and EXEC_OACC_SERIAL.
+	* resolve.c (gfc_resolve_blocks, gfc_resolve_code): Likewise.
+	* st.c (gfc_free_statement): Likewise.
+	* trans-openmp.c (gfc_trans_oacc_construct): Handle
+	EXEC_OACC_SERIAL.
+	(gfc_trans_oacc_combined_directive): Handle
+	EXEC_OACC_SERIAL_LOOP.
+	(gfc_trans_oacc_directive): Handle EXEC_OACC_SERIAL_LOOP and
+	EXEC_OACC_SERIAL.
+	* trans.c (trans_code): Likewise.
+
 2019-11-11  Janne Blomqvist  <jb@gcc.gnu.org>
 
         PR fortran/91828
diff --git a/gcc/fortran/dump-parse-tree.c b/gcc/fortran/dump-parse-tree.c
index 9d7aad1..253fe15 100644
--- a/gcc/fortran/dump-parse-tree.c
+++ b/gcc/fortran/dump-parse-tree.c
@@ -1654,6 +1654,8 @@ show_omp_node (int level, gfc_code *c)
     case EXEC_OACC_PARALLEL: name = "PARALLEL"; is_oacc = true; break;
     case EXEC_OACC_KERNELS_LOOP: name = "KERNELS LOOP"; is_oacc = true; break;
     case EXEC_OACC_KERNELS: name = "KERNELS"; is_oacc = true; break;
+    case EXEC_OACC_SERIAL_LOOP: name = "SERIAL LOOP"; is_oacc = true; break;
+    case EXEC_OACC_SERIAL: name = "SERIAL"; is_oacc = true; break;
     case EXEC_OACC_DATA: name = "DATA"; is_oacc = true; break;
     case EXEC_OACC_HOST_DATA: name = "HOST_DATA"; is_oacc = true; break;
     case EXEC_OACC_LOOP: name = "LOOP"; is_oacc = true; break;
@@ -1729,6 +1731,8 @@ show_omp_node (int level, gfc_code *c)
     case EXEC_OACC_PARALLEL:
     case EXEC_OACC_KERNELS_LOOP:
     case EXEC_OACC_KERNELS:
+    case EXEC_OACC_SERIAL_LOOP:
+    case EXEC_OACC_SERIAL:
     case EXEC_OACC_DATA:
     case EXEC_OACC_HOST_DATA:
     case EXEC_OACC_LOOP:
@@ -2918,6 +2922,8 @@ show_code_node (int level, gfc_code *c)
     case EXEC_OACC_PARALLEL:
     case EXEC_OACC_KERNELS_LOOP:
     case EXEC_OACC_KERNELS:
+    case EXEC_OACC_SERIAL_LOOP:
+    case EXEC_OACC_SERIAL:
     case EXEC_OACC_DATA:
     case EXEC_OACC_HOST_DATA:
     case EXEC_OACC_LOOP:
diff --git a/gcc/fortran/gfortran.h b/gcc/fortran/gfortran.h
index 920acda..e962db5 100644
--- a/gcc/fortran/gfortran.h
+++ b/gcc/fortran/gfortran.h
@@ -223,7 +223,8 @@ enum gfc_statement
   ST_OACC_END_DATA, ST_OACC_HOST_DATA, ST_OACC_END_HOST_DATA, ST_OACC_LOOP,
   ST_OACC_END_LOOP, ST_OACC_DECLARE, ST_OACC_UPDATE, ST_OACC_WAIT,
   ST_OACC_CACHE, ST_OACC_KERNELS_LOOP, ST_OACC_END_KERNELS_LOOP,
-  ST_OACC_ENTER_DATA, ST_OACC_EXIT_DATA, ST_OACC_ROUTINE,
+  ST_OACC_SERIAL_LOOP, ST_OACC_END_SERIAL_LOOP, ST_OACC_SERIAL,
+  ST_OACC_END_SERIAL, ST_OACC_ENTER_DATA, ST_OACC_EXIT_DATA, ST_OACC_ROUTINE,
   ST_OACC_ATOMIC, ST_OACC_END_ATOMIC,
   ST_OMP_ATOMIC, ST_OMP_BARRIER, ST_OMP_CRITICAL, ST_OMP_END_ATOMIC,
   ST_OMP_END_CRITICAL, ST_OMP_END_DO, ST_OMP_END_MASTER, ST_OMP_END_ORDERED,
@@ -2572,11 +2573,11 @@ enum gfc_exec_op
   EXEC_BACKSPACE, EXEC_ENDFILE, EXEC_INQUIRE, EXEC_REWIND, EXEC_FLUSH,
   EXEC_FORM_TEAM, EXEC_CHANGE_TEAM, EXEC_END_TEAM, EXEC_SYNC_TEAM,
   EXEC_LOCK, EXEC_UNLOCK, EXEC_EVENT_POST, EXEC_EVENT_WAIT, EXEC_FAIL_IMAGE,
-  EXEC_OACC_KERNELS_LOOP, EXEC_OACC_PARALLEL_LOOP, EXEC_OACC_ROUTINE,
-  EXEC_OACC_PARALLEL, EXEC_OACC_KERNELS, EXEC_OACC_DATA, EXEC_OACC_HOST_DATA,
-  EXEC_OACC_LOOP, EXEC_OACC_UPDATE, EXEC_OACC_WAIT, EXEC_OACC_CACHE,
-  EXEC_OACC_ENTER_DATA, EXEC_OACC_EXIT_DATA, EXEC_OACC_ATOMIC,
-  EXEC_OACC_DECLARE,
+  EXEC_OACC_KERNELS_LOOP, EXEC_OACC_PARALLEL_LOOP, EXEC_OACC_SERIAL_LOOP,
+  EXEC_OACC_ROUTINE, EXEC_OACC_PARALLEL, EXEC_OACC_KERNELS, EXEC_OACC_SERIAL,
+  EXEC_OACC_DATA, EXEC_OACC_HOST_DATA, EXEC_OACC_LOOP, EXEC_OACC_UPDATE,
+  EXEC_OACC_WAIT, EXEC_OACC_CACHE, EXEC_OACC_ENTER_DATA, EXEC_OACC_EXIT_DATA,
+  EXEC_OACC_ATOMIC, EXEC_OACC_DECLARE,
   EXEC_OMP_CRITICAL, EXEC_OMP_DO, EXEC_OMP_FLUSH, EXEC_OMP_MASTER,
   EXEC_OMP_ORDERED, EXEC_OMP_PARALLEL, EXEC_OMP_PARALLEL_DO,
   EXEC_OMP_PARALLEL_SECTIONS, EXEC_OMP_PARALLEL_WORKSHARE,
diff --git a/gcc/fortran/match.c b/gcc/fortran/match.c
index 4a31080..b594504 100644
--- a/gcc/fortran/match.c
+++ b/gcc/fortran/match.c
@@ -2860,7 +2860,8 @@ match_exit_cycle (gfc_statement st, gfc_exec_op op)
       && o != NULL
       && o->state == COMP_OMP_STRUCTURED_BLOCK
       && (o->head->op == EXEC_OACC_LOOP
-	  || o->head->op == EXEC_OACC_PARALLEL_LOOP))
+	  || o->head->op == EXEC_OACC_PARALLEL_LOOP
+	  || o->head->op == EXEC_OACC_SERIAL_LOOP))
     {
       int collapse = 1;
       gcc_assert (o->head->next != NULL
diff --git a/gcc/fortran/match.h b/gcc/fortran/match.h
index 611d796..7f3d356 100644
--- a/gcc/fortran/match.h
+++ b/gcc/fortran/match.h
@@ -146,6 +146,8 @@ match gfc_match_oacc_kernels (void);
 match gfc_match_oacc_kernels_loop (void);
 match gfc_match_oacc_parallel (void);
 match gfc_match_oacc_parallel_loop (void);
+match gfc_match_oacc_serial (void);
+match gfc_match_oacc_serial_loop (void);
 match gfc_match_oacc_enter_data (void);
 match gfc_match_oacc_exit_data (void);
 match gfc_match_oacc_routine (void);
diff --git a/gcc/fortran/openmp.c b/gcc/fortran/openmp.c
index ca34278..dc0521b 100644
--- a/gcc/fortran/openmp.c
+++ b/gcc/fortran/openmp.c
@@ -1964,6 +1964,12 @@ gfc_match_omp_clauses (gfc_omp_clauses **cp, const omp_mask mask,
    | OMP_CLAUSE_COPY | OMP_CLAUSE_COPYIN | OMP_CLAUSE_COPYOUT		      \
    | OMP_CLAUSE_CREATE | OMP_CLAUSE_PRESENT | OMP_CLAUSE_DEFAULT	      \
    | OMP_CLAUSE_WAIT)
+#define OACC_SERIAL_CLAUSES \
+  (omp_mask (OMP_CLAUSE_IF) | OMP_CLAUSE_ASYNC | OMP_CLAUSE_REDUCTION	      \
+   | OMP_CLAUSE_COPY | OMP_CLAUSE_COPYIN | OMP_CLAUSE_COPYOUT		      \
+   | OMP_CLAUSE_CREATE | OMP_CLAUSE_PRESENT | OMP_CLAUSE_DEVICEPTR	      \
+   | OMP_CLAUSE_PRIVATE | OMP_CLAUSE_FIRSTPRIVATE | OMP_CLAUSE_DEFAULT	      \
+   | OMP_CLAUSE_WAIT)
 #define OACC_DATA_CLAUSES \
   (omp_mask (OMP_CLAUSE_IF) | OMP_CLAUSE_DEVICEPTR  | OMP_CLAUSE_COPY	      \
    | OMP_CLAUSE_COPYIN | OMP_CLAUSE_COPYOUT | OMP_CLAUSE_CREATE		      \
@@ -1977,6 +1983,8 @@ gfc_match_omp_clauses (gfc_omp_clauses **cp, const omp_mask mask,
   (OACC_LOOP_CLAUSES | OACC_PARALLEL_CLAUSES)
 #define OACC_KERNELS_LOOP_CLAUSES \
   (OACC_LOOP_CLAUSES | OACC_KERNELS_CLAUSES)
+#define OACC_SERIAL_LOOP_CLAUSES \
+  (OACC_LOOP_CLAUSES | OACC_SERIAL_CLAUSES)
 #define OACC_HOST_DATA_CLAUSES omp_mask (OMP_CLAUSE_USE_DEVICE)
 #define OACC_DECLARE_CLAUSES \
   (omp_mask (OMP_CLAUSE_COPY) | OMP_CLAUSE_COPYIN | OMP_CLAUSE_COPYOUT	      \
@@ -2039,6 +2047,20 @@ gfc_match_oacc_kernels (void)
 
 
 match
+gfc_match_oacc_serial_loop (void)
+{
+  return match_acc (EXEC_OACC_SERIAL_LOOP, OACC_SERIAL_LOOP_CLAUSES);
+}
+
+
+match
+gfc_match_oacc_serial (void)
+{
+  return match_acc (EXEC_OACC_SERIAL, OACC_SERIAL_CLAUSES);
+}
+
+
+match
 gfc_match_oacc_data (void)
 {
   return match_acc (EXEC_OACC_DATA, OACC_DATA_CLAUSES);
@@ -3783,6 +3805,7 @@ oacc_is_loop (gfc_code *code)
 {
   return code->op == EXEC_OACC_PARALLEL_LOOP
 	 || code->op == EXEC_OACC_KERNELS_LOOP
+	 || code->op == EXEC_OACC_SERIAL_LOOP
 	 || code->op == EXEC_OACC_LOOP;
 }
 
@@ -4626,7 +4649,9 @@ resolve_omp_clauses (gfc_code *code, gfc_omp_clauses *omp_clauses,
 				 n->sym->name, name, &n->where);
 		  }
 		if (code
-		    && (oacc_is_loop (code) || code->op == EXEC_OACC_PARALLEL))
+		    && (oacc_is_loop (code)
+			|| code->op == EXEC_OACC_PARALLEL
+			|| code->op == EXEC_OACC_SERIAL))
 		  check_array_not_assumed (n->sym, n->where, name);
 		else if (n->sym->as && n->sym->as->type == AS_ASSUMED_SIZE)
 		  gfc_error ("Assumed size array %qs in %s clause at %L",
@@ -5818,6 +5843,8 @@ oacc_code_to_statement (gfc_code *code)
       return ST_OACC_PARALLEL;
     case EXEC_OACC_KERNELS:
       return ST_OACC_KERNELS;
+    case EXEC_OACC_SERIAL:
+      return ST_OACC_SERIAL;
     case EXEC_OACC_DATA:
       return ST_OACC_DATA;
     case EXEC_OACC_HOST_DATA:
@@ -5826,6 +5853,8 @@ oacc_code_to_statement (gfc_code *code)
       return ST_OACC_PARALLEL_LOOP;
     case EXEC_OACC_KERNELS_LOOP:
       return ST_OACC_KERNELS_LOOP;
+    case EXEC_OACC_SERIAL_LOOP:
+      return ST_OACC_SERIAL_LOOP;
     case EXEC_OACC_LOOP:
       return ST_OACC_LOOP;
     case EXEC_OACC_ATOMIC:
@@ -6163,6 +6192,7 @@ gfc_resolve_oacc_directive (gfc_code *code, gfc_namespace *ns ATTRIBUTE_UNUSED)
     {
     case EXEC_OACC_PARALLEL:
     case EXEC_OACC_KERNELS:
+    case EXEC_OACC_SERIAL:
     case EXEC_OACC_DATA:
     case EXEC_OACC_HOST_DATA:
     case EXEC_OACC_UPDATE:
@@ -6174,6 +6204,7 @@ gfc_resolve_oacc_directive (gfc_code *code, gfc_namespace *ns ATTRIBUTE_UNUSED)
       break;
     case EXEC_OACC_PARALLEL_LOOP:
     case EXEC_OACC_KERNELS_LOOP:
+    case EXEC_OACC_SERIAL_LOOP:
     case EXEC_OACC_LOOP:
       resolve_oacc_loop (code);
       break;
diff --git a/gcc/fortran/parse.c b/gcc/fortran/parse.c
index 15f6bf2..e44cc69 100644
--- a/gcc/fortran/parse.c
+++ b/gcc/fortran/parse.c
@@ -683,6 +683,9 @@ decode_oacc_directive (void)
       matcha ("end parallel loop", gfc_match_omp_eos_error,
 	      ST_OACC_END_PARALLEL_LOOP);
       matcha ("end parallel", gfc_match_omp_eos_error, ST_OACC_END_PARALLEL);
+      matcha ("end serial loop", gfc_match_omp_eos_error,
+	      ST_OACC_END_SERIAL_LOOP);
+      matcha ("end serial", gfc_match_omp_eos_error, ST_OACC_END_SERIAL);
       matcha ("enter data", gfc_match_oacc_enter_data, ST_OACC_ENTER_DATA);
       matcha ("exit data", gfc_match_oacc_exit_data, ST_OACC_EXIT_DATA);
       break;
@@ -705,6 +708,10 @@ decode_oacc_directive (void)
     case 'r':
       match ("routine", gfc_match_oacc_routine, ST_OACC_ROUTINE);
       break;
+    case 's':
+      matcha ("serial loop", gfc_match_oacc_serial_loop, ST_OACC_SERIAL_LOOP);
+      matcha ("serial", gfc_match_oacc_serial, ST_OACC_SERIAL);
+      break;
     case 'u':
       matcha ("update", gfc_match_oacc_update, ST_OACC_UPDATE);
       break;
@@ -1583,7 +1590,8 @@ next_statement (void)
   case ST_CRITICAL: \
   case ST_OACC_PARALLEL_LOOP: case ST_OACC_PARALLEL: case ST_OACC_KERNELS: \
   case ST_OACC_DATA: case ST_OACC_HOST_DATA: case ST_OACC_LOOP: \
-  case ST_OACC_KERNELS_LOOP: case ST_OACC_ATOMIC
+  case ST_OACC_KERNELS_LOOP: case ST_OACC_SERIAL_LOOP: case ST_OACC_SERIAL: \
+  case ST_OACC_ATOMIC
 
 /* Declaration statements */
 
@@ -2157,6 +2165,18 @@ gfc_ascii_statement (gfc_statement st)
     case ST_OACC_END_KERNELS_LOOP:
       p = "!$ACC END KERNELS LOOP";
       break;
+    case ST_OACC_SERIAL_LOOP:
+      p = "!$ACC SERIAL LOOP";
+      break;
+    case ST_OACC_END_SERIAL_LOOP:
+      p = "!$ACC END SERIAL LOOP";
+      break;
+    case ST_OACC_SERIAL:
+      p = "!$ACC SERIAL";
+      break;
+    case ST_OACC_END_SERIAL:
+      p = "!$ACC END SERIAL";
+      break;
     case ST_OACC_DATA:
       p = "!$ACC DATA";
       break;
@@ -5065,6 +5085,9 @@ parse_oacc_structured_block (gfc_statement acc_st)
     case ST_OACC_KERNELS:
       acc_end_st = ST_OACC_END_KERNELS;
       break;
+    case ST_OACC_SERIAL:
+      acc_end_st = ST_OACC_END_SERIAL;
+      break;
     case ST_OACC_DATA:
       acc_end_st = ST_OACC_END_DATA;
       break;
@@ -5096,7 +5119,7 @@ parse_oacc_structured_block (gfc_statement acc_st)
   pop_state ();
 }
 
-/* Parse the statements of OpenACC loop/parallel loop/kernels loop.  */
+/* Parse the statements of OpenACC 'loop', or combined compute 'loop'.  */
 
 static gfc_statement
 parse_oacc_loop (gfc_statement acc_st)
@@ -5149,6 +5172,7 @@ parse_oacc_loop (gfc_statement acc_st)
     gfc_warning (0, "Redundant !$ACC END LOOP at %C");
   if ((acc_st == ST_OACC_PARALLEL_LOOP && st == ST_OACC_END_PARALLEL_LOOP) ||
       (acc_st == ST_OACC_KERNELS_LOOP && st == ST_OACC_END_KERNELS_LOOP) ||
+      (acc_st == ST_OACC_SERIAL_LOOP && st == ST_OACC_END_SERIAL_LOOP) ||
       (acc_st == ST_OACC_LOOP && st == ST_OACC_END_LOOP))
     {
       gcc_assert (new_st.op == EXEC_NOP);
@@ -5488,6 +5512,7 @@ parse_executable (gfc_statement st)
 
 	case ST_OACC_PARALLEL_LOOP:
 	case ST_OACC_KERNELS_LOOP:
+	case ST_OACC_SERIAL_LOOP:
 	case ST_OACC_LOOP:
 	  st = parse_oacc_loop (st);
 	  if (st == ST_IMPLIED_ENDDO)
@@ -5496,6 +5521,7 @@ parse_executable (gfc_statement st)
 
 	case ST_OACC_PARALLEL:
 	case ST_OACC_KERNELS:
+	case ST_OACC_SERIAL:
 	case ST_OACC_DATA:
 	case ST_OACC_HOST_DATA:
 	  parse_oacc_structured_block (st);
@@ -6544,6 +6570,8 @@ is_oacc (gfc_state_data *sd)
     case EXEC_OACC_PARALLEL:
     case EXEC_OACC_KERNELS_LOOP:
     case EXEC_OACC_KERNELS:
+    case EXEC_OACC_SERIAL_LOOP:
+    case EXEC_OACC_SERIAL:
     case EXEC_OACC_DATA:
     case EXEC_OACC_HOST_DATA:
     case EXEC_OACC_LOOP:
diff --git a/gcc/fortran/resolve.c b/gcc/fortran/resolve.c
index a39b954..2371a9e 100644
--- a/gcc/fortran/resolve.c
+++ b/gcc/fortran/resolve.c
@@ -10576,6 +10576,8 @@ gfc_resolve_blocks (gfc_code *b, gfc_namespace *ns)
 	case EXEC_OACC_PARALLEL:
 	case EXEC_OACC_KERNELS_LOOP:
 	case EXEC_OACC_KERNELS:
+	case EXEC_OACC_SERIAL_LOOP:
+	case EXEC_OACC_SERIAL:
 	case EXEC_OACC_DATA:
 	case EXEC_OACC_HOST_DATA:
 	case EXEC_OACC_LOOP:
@@ -11539,6 +11541,8 @@ gfc_resolve_code (gfc_code *code, gfc_namespace *ns)
 	    case EXEC_OACC_PARALLEL:
 	    case EXEC_OACC_KERNELS_LOOP:
 	    case EXEC_OACC_KERNELS:
+	    case EXEC_OACC_SERIAL_LOOP:
+	    case EXEC_OACC_SERIAL:
 	    case EXEC_OACC_DATA:
 	    case EXEC_OACC_HOST_DATA:
 	    case EXEC_OACC_LOOP:
@@ -11952,6 +11956,8 @@ start:
 	case EXEC_OACC_PARALLEL:
 	case EXEC_OACC_KERNELS_LOOP:
 	case EXEC_OACC_KERNELS:
+	case EXEC_OACC_SERIAL_LOOP:
+	case EXEC_OACC_SERIAL:
 	case EXEC_OACC_DATA:
 	case EXEC_OACC_HOST_DATA:
 	case EXEC_OACC_LOOP:
diff --git a/gcc/fortran/st.c b/gcc/fortran/st.c
index ee18d7a..12eed71 100644
--- a/gcc/fortran/st.c
+++ b/gcc/fortran/st.c
@@ -202,6 +202,8 @@ gfc_free_statement (gfc_code *p)
     case EXEC_OACC_PARALLEL:
     case EXEC_OACC_KERNELS_LOOP:
     case EXEC_OACC_KERNELS:
+    case EXEC_OACC_SERIAL_LOOP:
+    case EXEC_OACC_SERIAL:
     case EXEC_OACC_DATA:
     case EXEC_OACC_HOST_DATA:
     case EXEC_OACC_LOOP:
diff --git a/gcc/fortran/trans-openmp.c b/gcc/fortran/trans-openmp.c
index dee7cc2..d9dfcab 100644
--- a/gcc/fortran/trans-openmp.c
+++ b/gcc/fortran/trans-openmp.c
@@ -3193,8 +3193,9 @@ gfc_trans_omp_code (gfc_code *code, bool force_empty)
   return stmt;
 }
 
-/* Trans OpenACC directives. */
-/* parallel, kernels, data and host_data. */
+/* Translate OpenACC 'parallel', 'kernels', 'serial', 'data', 'host_data'
+   construct. */
+
 static tree
 gfc_trans_oacc_construct (gfc_code *code)
 {
@@ -3210,6 +3211,9 @@ gfc_trans_oacc_construct (gfc_code *code)
       case EXEC_OACC_KERNELS:
 	construct_code = OACC_KERNELS;
 	break;
+      case EXEC_OACC_SERIAL:
+	construct_code = OACC_SERIAL;
+	break;
       case EXEC_OACC_DATA:
 	construct_code = OACC_DATA;
 	break;
@@ -4017,7 +4021,9 @@ gfc_trans_omp_do (gfc_code *code, gfc_exec_op op, stmtblock_t *pblock,
   return gfc_finish_block (&block);
 }
 
-/* parallel loop and kernels loop. */
+/* Translate combined OpenACC 'parallel loop', 'kernels loop', 'serial loop'
+   construct. */
+
 static tree
 gfc_trans_oacc_combined_directive (gfc_code *code)
 {
@@ -4035,6 +4041,9 @@ gfc_trans_oacc_combined_directive (gfc_code *code)
       case EXEC_OACC_KERNELS_LOOP:
 	construct_code = OACC_KERNELS;
 	break;
+      case EXEC_OACC_SERIAL_LOOP:
+	construct_code = OACC_SERIAL;
+	break;
       default:
 	gcc_unreachable ();
     }
@@ -5267,9 +5276,11 @@ gfc_trans_oacc_directive (gfc_code *code)
     {
     case EXEC_OACC_PARALLEL_LOOP:
     case EXEC_OACC_KERNELS_LOOP:
+    case EXEC_OACC_SERIAL_LOOP:
       return gfc_trans_oacc_combined_directive (code);
     case EXEC_OACC_PARALLEL:
     case EXEC_OACC_KERNELS:
+    case EXEC_OACC_SERIAL:
     case EXEC_OACC_DATA:
     case EXEC_OACC_HOST_DATA:
       return gfc_trans_oacc_construct (code);
diff --git a/gcc/fortran/trans.c b/gcc/fortran/trans.c
index 2f878f6..d9b2781 100644
--- a/gcc/fortran/trans.c
+++ b/gcc/fortran/trans.c
@@ -2137,6 +2137,8 @@ trans_code (gfc_code * code, tree cond)
 	case EXEC_OACC_KERNELS_LOOP:
 	case EXEC_OACC_PARALLEL:
 	case EXEC_OACC_PARALLEL_LOOP:
+	case EXEC_OACC_SERIAL:
+	case EXEC_OACC_SERIAL_LOOP:
 	case EXEC_OACC_ENTER_DATA:
 	case EXEC_OACC_EXIT_DATA:
 	case EXEC_OACC_ATOMIC: