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re PR tree-optimization/79090 (DSE wrongly removes store at variable offset) 

PR tree-optimization/79090
	* tree-ssa-dse.c (valid_ao_ref_for_dse): Reject zero length and
	variable length stores.
	(compute_trims): Delete dead assignment to *trim_tail.
	(dse_dom_walker::dse_optimize_stmt): Optimize mem* calls with
	zero length.

From-SVN: r244472
This commit is contained in:
Jeff Law 2017-01-15 02:34:01 -07:00 committed by Jeff Law
parent 3d812e26ea
commit 0cb4b758f5
2 changed files with 21 additions and 1 deletions
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9
gcc/ChangeLog
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@ -1,3 +1,12 @@
2017-01-14 Jeff Law <law@redhat.com>
PR tree-optimization/79090
* tree-ssa-dse.c (valid_ao_ref_for_dse): Reject zero length and
variable length stores.
(compute_trims): Delete dead assignment to *trim_tail.
(dse_dom_walker::dse_optimize_stmt): Optimize mem* calls with
zero length.
2017-01-14 Bernd Schmidt <bschmidt@redhat.com>
PR rtl-optimization/78626

13
gcc/tree-ssa-dse.c
View File

@ -129,6 +129,8 @@ valid_ao_ref_for_dse (ao_ref *ref)
{
return (ao_ref_base (ref)
&& ref->max_size != -1
&& ref->size != 0
&& ref->max_size == ref->size
&& (ref->offset % BITS_PER_UNIT) == 0
&& (ref->size % BITS_PER_UNIT) == 0
&& (ref->size != -1));
@ -221,7 +223,6 @@ compute_trims (ao_ref *ref, sbitmap live, int *trim_head, int *trim_tail)
the REF to compute the trims. */
/* Now identify how much, if any of the tail we can chop off. */
*trim_tail = 0;
int last_orig = (ref->size / BITS_PER_UNIT) - 1;
int last_live = bitmap_last_set_bit (live);
*trim_tail = (last_orig - last_live) & ~0x1;
@ -700,6 +701,16 @@ dse_dom_walker::dse_optimize_stmt (gimple_stmt_iterator *gsi)
case BUILT_IN_MEMMOVE:
case BUILT_IN_MEMSET:
{
/* Occasionally calls with an explicit length of zero
show up in the IL. It's pointless to do analysis
on them, they're trivially dead. */
tree size = gimple_call_arg (stmt, 2);
if (integer_zerop (size))
{
delete_dead_call (gsi);
return;
}
gimple *use_stmt;
enum dse_store_status store_status;
m_byte_tracking_enabled