use *_grow_cleared rather than *_grow on vect_unpromoted_value

vect_recog_over_widening_pattern is another spot which triggers the
right now commented out static assertion in vec.h which asserts
{quick,safe}_grow vec operations are only used with trivially default
constructible types.

I had a look at this and I think using quick_grow_cleared is best choice
here.  The nops is 2 or 1 most of the time, worst case 3, so the price of
extra initialization of 4 pointer-sized-or-less members times 1, 2 or 3
doesn't seem worth bothering, it is similar to the bitmap_head case where
we already pay the price for just one structure anytime we do
  vect_unpromoted_value unprom_diff;
(and later set_op on it) or even
  vect_unpromoted_value unprom0[2];

With this patch and Richard S's poly_int_pod removal the static_assert can
be enabled as well and gcc builds.

2023-09-29  Jakub Jelinek  <jakub@redhat.com>

	* tree-vect-patterns.cc (vect_recog_over_widening_pattern): Use
	quick_grow_cleared method on unprom rather than quick_grow.

diff --git a/gcc/tree-vect-patterns.cc b/gcc/tree-vect-patterns.cc
index a2ed0365b18cce927e4ebca5d4c15abd820355d3..6964c9986988d8f2f669bec9a4d187bef56c4f33 100644 (file)
--- a/gcc/tree-vect-patterns.cc
+++ b/gcc/tree-vect-patterns.cc
@@ -2944,7 +2944,7 @@ vect_recog_over_widening_pattern (vec_info *vinfo,
   /* Check the operands.  */
   unsigned int nops = gimple_num_ops (last_stmt) - first_op;
   auto_vec <vect_unpromoted_value, 3> unprom (nops);
-  unprom.quick_grow (nops);
+  unprom.quick_grow_cleared (nops);
   unsigned int min_precision = 0;
   bool single_use_p = false;
   for (unsigned int i = 0; i < nops; ++i)