[PATCH 09/10, OpenACC] Avoid introducing 'create' mapping clauses for loop index variables in kernels regions

[Kwok Cheung Yeung <kcy@codesourcery.com>]

This patch avoids adding CREATE mapping clauses for loop index variables. It 
also sets TREE_ADDRESSABLE on newly mapped declarations, which fixes an ICE that 
sometimes appears due to an assert firing in omp-low.c.

2019-07-16  Julian Brown  <julian@codesourcery.com>

	gcc/
	* omp-oacc-kernels.c (find_omp_for_index_vars_1,
	find_omp_for_index_vars): New functions.
	(maybe_build_inner_data_region): Add IDX_VARS argument. Don't add
	CREATE mapping clauses for loop index variables.  Set TREE_ADDRESSABLE
	flag on newly-mapped declarations as a side effect.
	(decompose_kernels_region_body): Call find_omp_for_index_vars.  Don't
	create PRESENT clause for loop index variables.  Pass index variable
	set to maybe_build_inner_data_region.
---
  gcc/omp-oacc-kernels.c | 58 ++++++++++++++++++++++++++++++++++++++++++++------
  1 file changed, 51 insertions(+), 7 deletions(-)

diff --git a/gcc/omp-oacc-kernels.c b/gcc/omp-oacc-kernels.c
index d65e6c6..2091385 100644
--- a/gcc/omp-oacc-kernels.c
+++ b/gcc/omp-oacc-kernels.c
@@ -766,6 +766,43 @@ flatten_binds (gbind *bind, bool include_toplevel_vars = false)
    return vars;
  }

+/* Recursively search BODY_SEQUENCE for 'for' loops, and record their loop
+   indices in IDX_VARS.  */
+
+static void
+find_omp_for_index_vars_1 (gimple_seq body_sequence, hash_set<tree> *idx_vars)
+{
+  gimple_stmt_iterator gsi;
+
+  for (gsi = gsi_start (body_sequence); !gsi_end_p (gsi); gsi_next (&gsi))
+    {
+      gimple *stmt = gsi_stmt (gsi);
+      gimple *for_stmt = top_level_omp_for_in_stmt (stmt);
+
+      if (for_stmt)
+        {
+	  tree idx = gimple_omp_for_index (for_stmt, 0);
+	  idx_vars->add (idx);
+	  find_omp_for_index_vars_1 (gimple_omp_body (for_stmt), idx_vars);
+	}
+      else if (gimple_code (stmt) == GIMPLE_BIND)
+	find_omp_for_index_vars_1 (gimple_bind_body (as_a <gbind *> (stmt)),
+				   idx_vars);
+    }
+}
+
+/* Find all loop index variables in a bind.  */
+
+static hash_set<tree>
+find_omp_for_index_vars (gbind *bind)
+{
+  hash_set<tree> idx_vars;
+
+  find_omp_for_index_vars_1 (gimple_bind_body (bind), &idx_vars);
+
+  return idx_vars;
+}
+
  /* Helper function for places where we construct data regions.  Wraps the BODY
     inside a try-finally construct at LOC that calls __builtin_GOACC_data_end
     in its cleanup block.  Returns this try statement.  */
@@ -784,13 +821,15 @@ make_data_region_try_statement (location_t loc, gimple *body)

  /* If INNER_BIND_VARS holds variables, build an OpenACC data region with
     location LOC containing BODY and having "create(var)" clauses for each
-   variable.  If INNER_CLEANUP is present, add a try-finally statement with
-   this cleanup code in the finally block.  Return the new data region, or
-   the original BODY if no data region was needed.  */
+   variable (such variables are also made addressable as a side effect).  If
+   INNER_CLEANUP is present, add a try-finally statement with this cleanup
+   code in the finally block.  Return the new data region, or the original
+   BODY if no data region was needed.  */

  static gimple *
  maybe_build_inner_data_region (location_t loc, gimple *body,
-                               tree inner_bind_vars, gimple *inner_cleanup)
+			       tree inner_bind_vars, gimple *inner_cleanup,
+			       hash_set<tree> *idx_vars)
  {
    /* Build data "create(var)" clauses for these local variables.
       Below we will add these to a data region enclosing the entire body
@@ -817,7 +856,7 @@ maybe_build_inner_data_region (location_t loc, gimple *body,
            else
              inner_bind_vars = next;
          }
-      else
+      else if (!idx_vars->contains (v))
          {
            /* Otherwise, build the map clause.  */
            tree new_clause = build_omp_clause (loc, OMP_CLAUSE_MAP);
@@ -825,6 +864,7 @@ maybe_build_inner_data_region (location_t loc, gimple *body,
            OMP_CLAUSE_DECL (new_clause) = v;
            OMP_CLAUSE_SIZE (new_clause) = DECL_SIZE_UNIT (v);
            OMP_CLAUSE_CHAIN (new_clause) = inner_data_clauses;
+	  TREE_ADDRESSABLE (v) = 1;
            inner_data_clauses = new_clause;

            prev_mapped_var = v;
@@ -1156,6 +1196,8 @@ decompose_kernels_region_body (gimple *kernels_region, 
tree kernels_clauses)
    tree inner_bind_vars = flatten_binds (kernels_bind);
    gimple_seq body_sequence = gimple_bind_body (kernels_bind);

+  hash_set<tree> idx_vars = find_omp_for_index_vars (kernels_bind);
+
    /* All these inner variables will get allocated on the device (below, by
       calling maybe_build_inner_data_region).  Here we create "present"
       clauses for them and add these clauses to the list of clauses to be
@@ -1163,7 +1205,9 @@ decompose_kernels_region_body (gimple *kernels_region, 
tree kernels_clauses)
    tree present_clauses = kernels_clauses;
    for (tree var = inner_bind_vars; var; var = TREE_CHAIN (var))
      {
-      if (!DECL_ARTIFICIAL (var) && TREE_CODE (var) != CONST_DECL)
+      if (!DECL_ARTIFICIAL (var)
+	  && TREE_CODE (var) != CONST_DECL
+	  && !idx_vars.contains (var))
          {
            tree present_clause = build_omp_clause (loc, OMP_CLAUSE_MAP);
            OMP_CLAUSE_SET_MAP_KIND (present_clause, GOMP_MAP_FORCE_PRESENT);
@@ -1342,7 +1386,7 @@ decompose_kernels_region_body (gimple *kernels_region, 
tree kernels_clauses)
    /* If we found variables declared in nested scopes, build a data region to
       map them to the device.  */
    body = maybe_build_inner_data_region (loc, body, inner_bind_vars,
-                                        inner_cleanup);
+                                        inner_cleanup, &idx_vars);

    return body;
  }
-- 
2.8.1