Re: [patch] Fix a couple of VEC_reserve uses, speed up update_ssa a bit

[Steven Bosscher]

On Fri, Aug 10, 2012 at 12:15 AM, Richard Henderson <r...@redhat.com> wrote:
> On 08/09/2012 03:06 PM, Steven Bosscher wrote:
>> +      unsigned old_len = name_to_id ? VEC_length (unsigned, name_to_id) : 0;
>> +      VEC_reserve (unsigned, heap, name_to_id, num_ssa_names - old_len);
>
> VEC_length already handles NULL input.

I didn't know that. Consider that hunk changed to this:

Index: tree-ssa-pre.c
===================================================================
--- tree-ssa-pre.c      (revision 190267)
+++ tree-ssa-pre.c      (working copy)
@@ -249,7 +249,8 @@ alloc_expression_id (pre_expr expr)
       /* VEC_safe_grow_cleared allocates no headroom.  Avoid frequent
         re-allocations by using VEC_reserve upfront.  There is no
         VEC_quick_grow_cleared unfortunately.  */
-      VEC_reserve (unsigned, heap, name_to_id, num_ssa_names);
+      unsigned old_len = VEC_length (unsigned, name_to_id);
+      VEC_reserve (unsigned, heap, name_to_id, num_ssa_names - old_len);
       VEC_safe_grow_cleared (unsigned, heap, name_to_id, num_ssa_names);
       gcc_assert (VEC_index (unsigned, name_to_id, version) == 0);
       VEC_replace (unsigned, name_to_id, version, expr->id);