OpenMP: Push attaches to end of clause list in "target" regions

This patch moves GOMP_MAP_ATTACH{_ZERO_LENGTH_ARRAY_SECTION} nodes to
the end of the clause list, for offload regions.  This ensures that when
we do the attach operation, both the "attachment point" and the target
region have both already been mapped on the target.  This avoids a
pathological case that can otherwise happen with struct sibling-list
handling.

This version of the patch moves the attach-node motion to
gimplify_adjust_omp_clauses.

2022-09-15  Julian Brown  <julian@codesourcery.com>

gcc/
	* gimplify.cc (omp_segregate_mapping_groups): Update comment.
	(gimplify_adjust_omp_clauses): Move ATTACH and
	ATTACH_ZERO_LENGTH_ARRAY_SECTION nodes to the end of the clause list
	for offloaded OpenMP regions.

gcc/testsuite/
	* g++.dg/gomp/target-lambda-1.C: Adjust expected scan output.

diff --git a/gcc/gimplify.cc b/gcc/gimplify.cc
index 2ae0c8cb2507fa578a0a8a4ea1c4cdc67dfc1ff4..4d032c6bf06372d07b27dfae740776417087ef79 100644 (file)
--- a/gcc/gimplify.cc
+++ b/gcc/gimplify.cc
@@ -9639,7 +9639,9 @@ omp_tsort_mapping_groups (vec<omp_mapping_group> *groups,
 /* Split INLIST into two parts, moving groups corresponding to
    ALLOC/RELEASE/DELETE mappings to one list, and other mappings to another.
    The former list is then appended to the latter.  Each sub-list retains the
-   order of the original list.  */
+   order of the original list.
+   Note that ATTACH nodes are later moved to the end of the list in
+   gimplify_adjust_omp_clauses, for target regions.  */
 
 static omp_mapping_group *
 omp_segregate_mapping_groups (omp_mapping_group *inlist)
@@ -12411,10 +12413,15 @@ gimplify_adjust_omp_clauses (gimple_seq *pre_p, gimple_seq body, tree *list_p,
            *list_p = c2;
          }
     }
+
+  tree attach_list = NULL_TREE;
+  tree *attach_tail = &attach_list;
+
   while ((c = *list_p) != NULL)
     {
       splay_tree_node n;
       bool remove = false;
+      bool move_attach = false;
 
       switch (OMP_CLAUSE_CODE (c))
        {
@@ -12576,6 +12583,19 @@ gimplify_adjust_omp_clauses (gimple_seq *pre_p, gimple_seq body, tree *list_p,
              remove = true;
              break;
            }
+         /* If we have a target region, we can push all the attaches to the
+            end of the list (we may have standalone "attach" operations
+            synthesized for GOMP_MAP_STRUCT nodes that must be processed after
+            the attachment point AND the pointed-to block have been mapped).
+            If we have something else, e.g. "enter data", we need to keep
+            "attach" nodes together with the previous node they attach to so
+            that separate "exit data" operations work properly (see
+            libgomp/target.c).  */
+         if ((ctx->region_type & ORT_TARGET) != 0
+             && (OMP_CLAUSE_MAP_KIND (c) == GOMP_MAP_ATTACH
+                 || (OMP_CLAUSE_MAP_KIND (c)
+                     == GOMP_MAP_ATTACH_ZERO_LENGTH_ARRAY_SECTION)))
+           move_attach = true;
          decl = OMP_CLAUSE_DECL (c);
          /* Data clauses associated with reductions must be
             compatible with present_or_copy.  Warn and adjust the clause
@@ -12890,10 +12910,25 @@ gimplify_adjust_omp_clauses (gimple_seq *pre_p, gimple_seq body, tree *list_p,
 
       if (remove)
        *list_p = OMP_CLAUSE_CHAIN (c);
+      else if (move_attach)
+       {
+         /* Remove attach node from here, separate out into its own list.  */
+         *attach_tail = c;
+         *list_p = OMP_CLAUSE_CHAIN (c);
+         OMP_CLAUSE_CHAIN (c) = NULL_TREE;
+         attach_tail = &OMP_CLAUSE_CHAIN (c);
+       }
       else
        list_p = &OMP_CLAUSE_CHAIN (c);
     }
 
+  /* Splice attach nodes at the end of the list.  */
+  if (attach_list)
+    {
+      *list_p = attach_list;
+      list_p = attach_tail;
+    }
+
   /* Add in any implicit data sharing.  */
   struct gimplify_adjust_omp_clauses_data data;
   if ((gimplify_omp_ctxp->region_type & ORT_ACC) == 0)

diff --git a/gcc/testsuite/g++.dg/gomp/target-lambda-1.C b/gcc/testsuite/g++.dg/gomp/target-lambda-1.C
index bff7fa7c669241048682cf026f9fdf029a9eec57..5ce8ceadb194d14320ad0ea2201afe8459d04bcf 100644 (file)
--- a/gcc/testsuite/g++.dg/gomp/target-lambda-1.C
+++ b/gcc/testsuite/g++.dg/gomp/target-lambda-1.C
@@ -87,7 +87,7 @@ int main (void)
   return 0;
 }
 
-/* { dg-final { scan-tree-dump {#pragma omp target num_teams.* firstprivate\(b\) map\(alloc:MEM.* \[len: 0\]\) map\(firstprivate:iptr \[pointer assign, bias: 0\]\) map\(alloc:MEM.* \[len: 0\]\) map\(firstprivate:this \[pointer assign, bias: 0\]\) map\(to:\*__closure \[len: [0-9]+\]\) map\(firstprivate:__closure \[pointer assign, bias: 0\]\) map\(tofrom:\*_[0-9]+ \[len: [0-9]+\]\) map\(always_pointer:__closure->__this \[pointer assign, bias: 0\]\) map\(from:mapped \[len: [0-9]+\]\) map\(alloc:\*_[0-9]+ \[len: 0\]\) map\(attach_zero_length_array_section:__closure->__iptr \[bias: 0\]\) map\(alloc:\*_[0-9]+ \[len: 0\]\) map\(attach_zero_length_array_section:_[0-9]+->ptr \[bias: 0\]\)} "gimple" } } */
+/* { dg-final { scan-tree-dump {#pragma omp target num_teams.* firstprivate\(b\) map\(alloc:MEM.* \[len: 0\]\) map\(firstprivate:iptr \[pointer assign, bias: 0\]\) map\(alloc:MEM.* \[len: 0\]\) map\(firstprivate:this \[pointer assign, bias: 0\]\) map\(to:\*__closure \[len: [0-9]+\]\) map\(firstprivate:__closure \[pointer assign, bias: 0\]\) map\(tofrom:\*_[0-9]+ \[len: [0-9]+\]\) map\(always_pointer:__closure->__this \[pointer assign, bias: 0\]\) map\(from:mapped \[len: [0-9]+\]\) map\(alloc:\*_[0-9]+ \[len: 0\]\) map\(alloc:\*_[0-9]+ \[len: 0\]\) map\(attach_zero_length_array_section:__closure->__iptr \[bias: 0\]\) map\(attach_zero_length_array_section:_[0-9]+->ptr \[bias: 0\]\)} "gimple" } } */
 
 /* { dg-final { scan-tree-dump {#pragma omp target num_teams.* firstprivate\(end\) firstprivate\(begin\) map\(to:loop \[len: [0-9]+\]\) map\(alloc:\*_[0-9]+ \[len: 0\]\) map\(attach_zero_length_array_section:loop\.__data1 \[bias: 0\]\)} "gimple" } } */