re PR c++/90801 (A recurring hang)

2019-06-11  Richard Biener  <rguenther@suse.de>

	PR c++/90801
	* typeck2.c (split_nonconstant_init_1): Avoid ordered remove
	from CONSTRUCTOR by marking to remove elements and doing all
	of them in a O(n) scan.

From-SVN: r272156

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 757f3fccf31f5ccd596c4686f60884ad4480889c..e067ff7a0e092fb6c18659295298bd0aee891d74 100644 (file)
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,10 @@
+2019-06-11  Richard Biener  <rguenther@suse.de>
+
+       PR c++/90801
+       * typeck2.c (split_nonconstant_init_1): Avoid ordered remove
+       from CONSTRUCTOR by marking to remove elements and doing all
+       of them in a O(n) scan.
+
 2019-06-11  Jakub Jelinek  <jakub@redhat.com>
 
        PR c++/90810

diff --git a/gcc/cp/typeck2.c b/gcc/cp/typeck2.c
index e9f759d4213faa3d324abd85f55a2febc031d245..dd7e2cb024c22107d5ac965e45830a19b68273d9 100644 (file)
--- a/gcc/cp/typeck2.c
+++ b/gcc/cp/typeck2.c
@@ -603,7 +603,7 @@ cxx_incomplete_type_error (location_t loc, const_tree value, const_tree type)
 static bool
 split_nonconstant_init_1 (tree dest, tree init)
 {
-  unsigned HOST_WIDE_INT idx;
+  unsigned HOST_WIDE_INT idx, tidx;
   tree field_index, value;
   tree type = TREE_TYPE (dest);
   tree inner_type = NULL;
@@ -657,7 +657,8 @@ split_nonconstant_init_1 (tree dest, tree init)
              if (!split_nonconstant_init_1 (sub, value))
                complete_p = false;
              else
-               CONSTRUCTOR_ELTS (init)->ordered_remove (idx--);
+               /* Mark element for removal.  */
+               CONSTRUCTOR_ELT (init, idx)->index = NULL_TREE;
              num_split_elts++;
            }
          else if (!initializer_constant_valid_p (value, inner_type))
@@ -665,15 +666,8 @@ split_nonconstant_init_1 (tree dest, tree init)
              tree code;
              tree sub;
 
-             /* FIXME: Ordered removal is O(1) so the whole function is
-                worst-case quadratic. This could be fixed using an aside
-                bitmap to record which elements must be removed and remove
-                them all at the same time. Or by merging
-                split_non_constant_init into process_init_constructor_array,
-                that is separating constants from non-constants while building
-                the vector.  */
-             CONSTRUCTOR_ELTS (init)->ordered_remove (idx);
-             --idx;
+             /* Mark element for removal.  */
+             CONSTRUCTOR_ELT (init, idx)->index = NULL_TREE;
 
              if (TREE_CODE (field_index) == RANGE_EXPR)
                {
@@ -711,6 +705,21 @@ split_nonconstant_init_1 (tree dest, tree init)
              num_split_elts++;
            }
        }
+      if (num_split_elts != 0)
+       {
+         /* Perform the delayed ordered removal of non-constant elements
+            we split out.  */
+         for (tidx = 0, idx = 0; idx < CONSTRUCTOR_NELTS (init); ++idx)
+           if (CONSTRUCTOR_ELT (init, idx)->index == NULL_TREE)
+             ;
+           else
+             {
+               if (tidx != idx)
+                 *CONSTRUCTOR_ELT (init, tidx) = *CONSTRUCTOR_ELT (init, idx);
+               ++tidx;
+             }
+         vec_safe_truncate (CONSTRUCTOR_ELTS (init), tidx);
+       }
       break;
 
     case VECTOR_TYPE: