On Fri, 16 Sep 2016, Richard Biener wrote:
> On Fri, 16 Sep 2016, Bernhard Reutner-Fischer wrote:
>
> > On 15 September 2016 09:08:36 CEST, Richard Biener <rguent...@suse.de>
> > wrote:
> > >
> > >Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
> > >
> >
> > >+ /* Likewise if we simplified to sth not queued for insertion. */
> > >+ bool found = false;
> > >+ gsi = gsi_start (forced_stmts);
> > >+ for (; !gsi_end_p (gsi); gsi_next (&gsi))
> > >+ {
> > >+ gimple *stmt = gsi_stmt (gsi);
> > >+ tree forcedname = gimple_get_lhs (stmt);
> > >+ if (forcedname == folded)
> > {
> > >+ found = true;
> >
> > break;}
> >
> > Or do we fix up such code anyway somewhere?
>
> We don't -- I guess it would be an interesting transform but difficult
> in this case as gimple_get_lhs might have side-effects we cannot skip.
>
> It might fit loop splitting which would split it "dynamically" into
> a head running until we set found to true, skipping to the tail
> that has the loop with omitted guard and found = true setting.
> If the loop ends up with no side-effects it should end up being
> removed. If not it might actually not be a desirable transform due
> to code-size.
>
> I'll fixup the PRE code.
Bootstrapped / tested on x86_64-unknown-linux-gnu.
Richard.
2016-09-19 Richard Biener <rguent...@suse.de>
PR tree-optimization/77514
* tree-ssa-pre.c (create_expression_by_pieces): Optimize
search for folded stmt.
Index: gcc/tree-ssa-pre.c
===================================================================
--- gcc/tree-ssa-pre.c (revision 240176)
+++ gcc/tree-ssa-pre.c (working copy)
@@ -2881,13 +2881,16 @@ create_expression_by_pieces (basic_block
}
/* Likewise if we simplified to sth not queued for insertion. */
bool found = false;
- gsi = gsi_start (forced_stmts);
- for (; !gsi_end_p (gsi); gsi_next (&gsi))
+ gsi = gsi_last (forced_stmts);
+ for (; !gsi_end_p (gsi); gsi_prev (&gsi))
{
gimple *stmt = gsi_stmt (gsi);
tree forcedname = gimple_get_lhs (stmt);
if (forcedname == folded)
- found = true;
+ {
+ found = true;
+ break;
+ }
}
if (! found)
{
