[gcc/devel/omp/gcc-12] Reinstate kernels-restrict behaviour

[gcc/devel/omp/gcc-12] Reinstate kernels-restrict behaviour

[Kwok Yeung]

https://gcc.gnu.org/g:90d4c72130b639d27509d749a2c272b5315dd5c2

commit 90d4c72130b639d27509d749a2c272b5315dd5c2
Author: Julian Brown <julian@codesourcery.com>
Date:   Wed Mar 6 14:44:56 2019 -0800

    Reinstate kernels-restrict behaviour
    
    This patch contains a small fix for upstream churn relative to the last version
    posted.
    
    2018-09-20  Cesar Philippidis  <cesar@codesourcery.com>
                Julian Brown  <julian@codesourcery.com>
    
            * omp-low.c (install_var_field): New base_pointer_restrict
            argument.
            (scan_sharing_clauses): Update call to install_var_field.
            (omp_target_base_pointers_restrict_p): New function.
            (scan_omp_target): Update call to install_var_field.

Diff:
---
 gcc/ChangeLog.omp |  9 ++++++
 gcc/omp-low.cc    | 88 +++++++++++++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 91 insertions(+), 6 deletions(-)

diff --git a/gcc/ChangeLog.omp b/gcc/ChangeLog.omp
index d1a9bcef523..6c0729986fa 100644
--- a/gcc/ChangeLog.omp
+++ b/gcc/ChangeLog.omp
@@ -1,3 +1,12 @@
+2018-09-20  Cesar Philippidis  <cesar@codesourcery.com>
+	    Julian Brown  <julian@codesourcery.com>
+
+	* omp-low.c (install_var_field): New base_pointer_restrict
+	argument.
+	(scan_sharing_clauses): Update call to install_var_field.
+	(omp_target_base_pointers_restrict_p): New function.
+	(scan_omp_target): Update call to install_var_field.
+
 2018-10-30  Cesar Philippidis  <cesar@codesourcery.com>
 
 	* config/nvptx/nvptx.cc (nvptx_propagate_unified): New.
diff --git a/gcc/omp-low.cc b/gcc/omp-low.cc
index 70a6dc3c399..edc22e25e91 100644
--- a/gcc/omp-low.cc
+++ b/gcc/omp-low.cc
@@ -777,7 +777,8 @@ build_sender_ref (tree var, omp_context *ctx)
    BASE_POINTERS_RESTRICT, declare the field with restrict.  */
 
 static void
-install_var_field (tree var, bool by_ref, int mask, omp_context *ctx)
+install_var_field (tree var, bool by_ref, int mask, omp_context *ctx,
+		   bool base_pointers_restrict = false)
 {
   tree field, type, sfield = NULL_TREE;
   splay_tree_key key = (splay_tree_key) var;
@@ -816,7 +817,11 @@ install_var_field (tree var, bool by_ref, int mask, omp_context *ctx)
       type = build_pointer_type (build_pointer_type (type));
     }
   else if (by_ref)
-    type = build_pointer_type (type);
+    {
+      type = build_pointer_type (type);
+      if (base_pointers_restrict)
+	type = build_qualified_type (type, TYPE_QUAL_RESTRICT);
+    }
   else if ((mask & (32 | 3)) == 1
 	   && omp_privatize_by_reference (var))
     type = TREE_TYPE (type);
@@ -1256,10 +1261,12 @@ fixup_child_record_type (omp_context *ctx)
 }
 
 /* Instantiate decls as necessary in CTX to satisfy the data sharing
-   specified by CLAUSES.  */
+   specified by CLAUSES.  If BASE_POINTERS_RESTRICT, install var field with
+   restrict.  */
 
 static void
-scan_sharing_clauses (tree clauses, omp_context *ctx)
+scan_sharing_clauses (tree clauses, omp_context *ctx,
+		      bool base_pointers_restrict = false)
 {
   tree c, decl;
   bool scan_array_reductions = false;
@@ -1796,7 +1803,8 @@ scan_sharing_clauses (tree clauses, omp_context *ctx)
 		      && TREE_CODE (TREE_TYPE (decl)) == ARRAY_TYPE)
 		    install_var_field (decl, true, 7, ctx);
 		  else
-		    install_var_field (decl, true, 3, ctx);
+		    install_var_field (decl, true, 3, ctx,
+				       base_pointers_restrict);
 		  if (is_gimple_omp_offloaded (ctx->stmt)
 		      && !(is_gimple_omp_oacc (ctx->stmt)
 			   && OMP_CLAUSE_MAP_IN_REDUCTION (c)))
@@ -3197,6 +3205,68 @@ scan_omp_single (gomp_single *stmt, omp_context *outer_ctx)
     layout_type (ctx->record_type);
 }
 
+/* Return true if the CLAUSES of an omp target guarantee that the base pointers
+   used in the corresponding offloaded function are restrict.  */
+
+static bool
+omp_target_base_pointers_restrict_p (tree clauses)
+{
+  /* The analysis relies on the GOMP_MAP_FORCE_* mapping kinds, which are only
+     used by OpenACC.  */
+  if (flag_openacc == 0)
+    return false;
+
+  /* I.  Basic example:
+
+       void foo (void)
+       {
+	 unsigned int a[2], b[2];
+
+	 #pragma acc kernels \
+	   copyout (a) \
+	   copyout (b)
+	 {
+	   a[0] = 0;
+	   b[0] = 1;
+	 }
+       }
+
+     After gimplification, we have:
+
+       #pragma omp target oacc_kernels \
+	 map(force_from:a [len: 8]) \
+	 map(force_from:b [len: 8])
+       {
+	 a[0] = 0;
+	 b[0] = 1;
+       }
+
+     Because both mappings have the force prefix, we know that they will be
+     allocated when calling the corresponding offloaded function, which means we
+     can mark the base pointers for a and b in the offloaded function as
+     restrict.  */
+
+  tree c;
+  for (c = clauses; c; c = OMP_CLAUSE_CHAIN (c))
+    {
+      if (OMP_CLAUSE_CODE (c) != OMP_CLAUSE_MAP)
+	return false;
+
+      switch (OMP_CLAUSE_MAP_KIND (c))
+	{
+	case GOMP_MAP_FORCE_ALLOC:
+	case GOMP_MAP_FORCE_TO:
+	case GOMP_MAP_FORCE_FROM:
+	case GOMP_MAP_FORCE_TOFROM:
+	  break;
+	default:
+	  return false;
+	}
+    }
+
+  return true;
+}
+
 /* Reorder clauses so that non-contiguous array map clauses are placed at the very
    front of the chain.  */
 
@@ -3269,13 +3339,19 @@ scan_omp_target (gomp_target *stmt, omp_context *outer_ctx)
 
   tree clauses = gimple_omp_target_clauses (stmt);
 
+  bool base_pointers_restrict = false;
   if (offloaded)
     {
       create_omp_child_function (ctx, false);
       gimple_omp_target_set_child_fn (stmt, ctx->cb.dst_fn);
+
+      base_pointers_restrict = omp_target_base_pointers_restrict_p (clauses);
+      if (base_pointers_restrict && dump_file && (dump_flags & TDF_DETAILS))
+	fprintf (dump_file,
+		 "Base pointers in offloaded function are restrict\n");
     }
 
-  scan_sharing_clauses (clauses, ctx);
+  scan_sharing_clauses (clauses, ctx, base_pointers_restrict);
   scan_omp (gimple_omp_body_ptr (stmt), ctx);
 
   if (TYPE_FIELDS (ctx->record_type) == NULL)