Remove fishy self-assignment in omp-low.c [PR94629]

The PR noticed that omp-low.c contains a self-assignment in the
function new_omp_context:

if (outer_ctx) {
    ...
    ctx->outer_reduction_clauses = ctx->outer_reduction_clauses;

This is obviously useless.  The original intention might have been
to copy the field from the outer_ctx to ctx.  Since this is done
(properly) in the only function where this field is actually used
(in function scan_omp_for) and the field is being initialized to zero
during the struct allocation, there is no need to attempt to do
anything to this field in new_omp_context. Thus this commit
removes any assignment to the field from new_omp_context.

2020-04-21  Frederik Harwath  <frederik@codesourcery.com>

	PR other/94629
	* gcc/omp-low.c (new_omp_context): Remove assignments to
	ctx->outer_reduction_clauses and ctx->local_reduction_clauses.

Reviewed-by: Thomas Schwinge  <thomas@codesourcery.com>

gcc/ChangeLog

+2020-04-21  Frederik Harwath  <frederik@codesourcery.com>
+
+	PR other/94629
+	* omp-low.c (new_omp_context): Remove assignments to
+	ctx->outer_reduction_clauses and ctx->local_reduction_clauses.
+
 2020-04-20  Andreas Krebbel  <krebbel@linux.ibm.com>
 
 	* config/s390/vector.md ("popcountv8hi2_vx", "popcountv4si2_vx")

gcc/omp-low.c

@@ -128,10 +128,16 @@ struct omp_context
      corresponding tracking loop iteration variables.  */
   hash_map<tree, tree> *lastprivate_conditional_map;
 
-  /* A tree_list of the reduction clauses in this context.  */
+  /* A tree_list of the reduction clauses in this context. This is
+    only used for checking the consistency of OpenACC reduction
+    clauses in scan_omp_for and is not guaranteed to contain a valid
+    value outside of this function. */
   tree local_reduction_clauses;
 
-  /* A tree_list of the reduction clauses in outer contexts.  */
+  /* A tree_list of the reduction clauses in outer contexts. This is
+    only used for checking the consistency of OpenACC reduction
+    clauses in scan_omp_for and is not guaranteed to contain a valid
+    value outside of this function. */
   tree outer_reduction_clauses;
 
   /* Nesting depth of this context.  Used to beautify error messages re
@@ -931,8 +937,6 @@ new_omp_context (gimple *stmt, omp_context *outer_ctx)
       ctx->outer = outer_ctx;
       ctx->cb = outer_ctx->cb;
       ctx->cb.block = NULL;
-      ctx->local_reduction_clauses = NULL;
-      ctx->outer_reduction_clauses = ctx->outer_reduction_clauses;
       ctx->depth = outer_ctx->depth + 1;
     }
   else
@@ -948,8 +952,6 @@ new_omp_context (gimple *stmt, omp_context *outer_ctx)
       ctx->cb.transform_call_graph_edges = CB_CGE_MOVE;
       ctx->cb.adjust_array_error_bounds = true;
       ctx->cb.dont_remap_vla_if_no_change = true;
-      ctx->local_reduction_clauses = NULL;
-      ctx->outer_reduction_clauses = NULL;
       ctx->depth = 1;
     }