diff mbox

Fix PR77514

Message ID alpine.LSU.2.11.1609190852450.26629@t29.fhfr.qr
State New
Headers show

Commit Message

Richard Biener Sept. 19, 2016, 6:53 a.m. UTC 
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 <rguenther@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  <rguenther@suse.de>

	PR tree-optimization/77514
	* tree-ssa-pre.c (create_expression_by_pieces): Optimize
	search for folded stmt.
diff mbox

Patch

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)
     {