[gcc/devel/omp/gcc-11] Allow gang-level reductions in OpenACC routines with gang-level parallelism

[gcc/devel/omp/gcc-11] Allow gang-level reductions in OpenACC routines with gang-level parallelism

[Kwok Yeung]

https://gcc.gnu.org/g:ec9998a4c3f31dafe2406064fa236f59972170c0

commit ec9998a4c3f31dafe2406064fa236f59972170c0
Author: Kwok Cheung Yeung <kcy@codesourcery.com>
Date:   Thu Mar 19 09:44:18 2020 -0700

    Allow gang-level reductions in OpenACC routines with gang-level parallelism
    
    2020-03-19  Kwok Cheung Yeung  <kcy@codesourcery.com>
    
            gcc/
            * omp-offload.c (oacc_loop_auto_partitions): Check for 'omp declare
            target' attributes with a gang clause attached.

Diff:
---
 gcc/ChangeLog.omp |  5 +++++
 gcc/omp-offload.c | 24 +++++++++++++++++++++---
 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/gcc/ChangeLog.omp b/gcc/ChangeLog.omp
index bd5d7de4cd7..301a9ece91b 100644
--- a/gcc/ChangeLog.omp
+++ b/gcc/ChangeLog.omp
@@ -1,3 +1,8 @@
+2020-03-19  Kwok Cheung Yeung  <kcy@codesourcery.com>
+
+	* omp-offload.c (oacc_loop_auto_partitions): Check for 'omp declare
+	target' attributes with a gang clause attached.
+
 2020-03-16  Tobias Burnus  <tobias@codesourcery.com>
 
 	* omp-oacc-kernels-decompose.cc (maybe_build_inner_data_region):
diff --git a/gcc/omp-offload.c b/gcc/omp-offload.c
index b10047b96d2..21e9b923443 100644
--- a/gcc/omp-offload.c
+++ b/gcc/omp-offload.c
@@ -1620,10 +1620,28 @@ oacc_loop_auto_partitions (oacc_loop *loop, unsigned outer_mask,
 
       /* Orphan reductions cannot have gang partitioning.  */
       if ((loop->flags & OLF_REDUCTION)
-	  && oacc_get_fn_attrib (current_function_decl)
-	  && !lookup_attribute ("omp target entrypoint",
+	  && oacc_get_fn_attrib (current_function_decl))
+	{
+	  bool gang_p = false;
+	  tree attr
+	      = lookup_attribute ("omp declare target",
+				  DECL_ATTRIBUTES (current_function_decl));
+
+	  if (attr)
+	    for (tree c = TREE_VALUE (attr); c; c = OMP_CLAUSE_CHAIN (c))
+	      if (OMP_CLAUSE_CODE (c) == OMP_CLAUSE_GANG)
+		{
+		  gang_p = true;
+		  break;
+		}
+
+	  if (lookup_attribute ("omp target entrypoint",
 				DECL_ATTRIBUTES (current_function_decl)))
-	this_mask = GOMP_DIM_MASK (GOMP_DIM_WORKER);
+	    gang_p = true;
+
+	  if (!gang_p)
+	    this_mask = GOMP_DIM_MASK (GOMP_DIM_WORKER);
+	}
 
       /* Find the first outermost available partition. */
       while (this_mask <= outer_mask)