[Bug tree-optimization/63844] [4.8/4.9/5 Regression] open mp parallelization prevents vectorization

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63844

--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
Ok, I think Tom had a similar patch for this but passing the .omp_data_i by
effective "reference" (restrict qualified pointer and DECL_BY_REFERENCE)
fixes this.

Index: gcc/omp-low.c
===================================================================
--- gcc/omp-low.c       (revision 217692)
+++ gcc/omp-low.c       (working copy)
@@ -1517,7 +1517,8 @@ fixup_child_record_type (omp_context *ct
       layout_type (type);
     }

-  TREE_TYPE (ctx->receiver_decl) = build_pointer_type (type);
+  TREE_TYPE (ctx->receiver_decl)
+    = build_qualified_type (build_pointer_type (type), TYPE_QUAL_RESTRICT);
 }

 /* Instantiate decls as necessary in CTX to satisfy the data sharing
@@ -2006,6 +2007,7 @@ create_omp_child_function (omp_context *
   DECL_NAMELESS (t) = 1;
   DECL_ARG_TYPE (t) = ptr_type_node;
   DECL_CONTEXT (t) = current_function_decl;
+  DECL_BY_REFERENCE (t) = 1;
   TREE_USED (t) = 1;
   if (cilk_for_count)
     DECL_CHAIN (t) = DECL_ARGUMENTS (decl);

there are more similar objects built, so the above may not fully optimize
all cases.