[COMMITTED] algol68: optimize a68_low_dup for non-row values that do not contain rows

[Jose E. Marchesi]

---
 gcc/algol68/a68-low.cc | 58 +++++++++++++++++++++---------------------
 1 file changed, 29 insertions(+), 29 deletions(-)

diff --git a/gcc/algol68/a68-low.cc b/gcc/algol68/a68-low.cc
index f54158bb26c..04da444609f 100644
--- a/gcc/algol68/a68-low.cc
+++ b/gcc/algol68/a68-low.cc
@@ -474,9 +474,8 @@ a68_low_dup (tree expr, bool use_heap)
 	}
       else
 	{
-	  /* We calculate num_elems by dividing new_elements_size by the byte
-	     size of the type of the elements.  This includes elements that are
-	     not accessible due to trimming.  */
+	  /* Note that num_elems includes elements that are not accessible due
+	     to trimming.  */
 	  tree num_elems = a68_lower_tmpvar ("numelems%", size_type_node,
 					     fold_build2 (TRUNC_DIV_EXPR, sizetype,
 							  new_elements_size,
@@ -537,35 +536,35 @@ a68_low_dup (tree expr, bool use_heap)
 			       new_elements,
 			       new_elements_size);
     }
+  else if (!HAS_ROWS (m))
+    {
+      /* Non-multiple values that do not contain rows do not need to be dupped,
+	 since they can be just moved around using the semantics of
+	 MODIFY_EXPR.  */
+      dup = expr;
+    }
   else if (A68_STRUCT_TYPE_P (type))
     {
-      if (TREE_CONSTANT (expr))
-	/* Copying the array descriptor is enough, it can share the constant
-	   elements with the original arrays.  */
-	dup = expr;
-      else
+      /* Since struct value can contain multiples and unions and other values
+	 that require deep copy, we cannot simply rely on the C semantics of a
+	 MODIFY_EXPR.  */
+      tree struct_type = type;
+      vec <constructor_elt, va_gc> *ce = NULL;
+
+      expr = save_expr (expr);
+      for (tree field = TYPE_FIELDS (struct_type);
+	   field;
+	   field = TREE_CHAIN (field))
 	{
-	  /* Since struct value can contain multiples and unions and other
-	     values that require deep copy, we cannot simply rely on the C
-	     semantics of a MODIFY_EXPR.  */
-	  tree struct_type = type;
-	  vec <constructor_elt, va_gc> *ce = NULL;
-
-	  expr = save_expr (expr);
-	  for (tree field = TYPE_FIELDS (struct_type);
-	       field;
-	       field = TREE_CHAIN (field))
-	    {
-	      CONSTRUCTOR_APPEND_ELT (ce, field,
-				      a68_low_dup (fold_build3 (COMPONENT_REF,
-								TREE_TYPE (field),
-								expr,
-								field,
-								NULL_TREE),
-						   use_heap));
-	    }
-	  dup = build_constructor (struct_type, ce);
+	  CONSTRUCTOR_APPEND_ELT (ce, field,
+				  a68_low_dup (fold_build3 (COMPONENT_REF,
+							    TREE_TYPE (field),
+							    expr,
+							    field,
+							    NULL_TREE),
+					       use_heap));
 	}
+      dup = build_constructor (struct_type, ce);
     }
   else if (A68_UNION_TYPE_P (type))
     {
@@ -629,7 +628,8 @@ a68_low_dup (tree expr, bool use_heap)
       dup = a68_pop_range ();
     }
   else
-    dup = expr;
+    /* Not an Algol 68 value.  */
+    gcc_unreachable ();
 
   return dup;
 }
-- 
2.30.2