[PATCH] Don't cross-jump in between frame related and non-frame related insns (PR target/80102, take 2)

[Jakub Jelinek <jakub at redhat dot com>]

On Tue, Mar 21, 2017 at 08:38:20AM +1000, Richard Henderson wrote:
> On 03/21/2017 07:15 AM, Jakub Jelinek wrote:
> > Not really sure what we should do if both i1 and i2 are frame related, shall
> > we check for each of the CFA reg notes if they are available and equal?
> > Or punt if either of the insns is frame related?
> 
> I would punt if either is frame related.

Ok, I'll test then the following patch and gather some statistic on how
often we trigger this.

> As an aside, if the length of "blockage" is corrected to 0, does
> cross-jumping skip this case?  Because replacing a simple_return with a
> direct branch to a simple_return is not a win.  But of course at the moment
> cross-jumping thinks it is eliminating the second blockage as well...

I don't think cross-jumping counts anything but the number of active_insn_p,
at least I can't find any get_attr_length uses outside of final.c in the
generic code (and just very few (shrink-wrap and bb-reorder)
get_attr_min_length calls).  So shall cross-jumping only count
ifdef HAVE_attr_length insns with get_attr_length > 0?

2017-03-21  Jakub Jelinek  <jakub@redhat.com>

	PR target/80102
	* cfgcleanup.c (old_insns_match_p): Don't cross-jump frame related
	insns.

	* g++.dg/opt/pr80102.C: New test.

--- gcc/cfgcleanup.c.jj	2017-01-09 22:46:03.000000000 +0100
+++ gcc/cfgcleanup.c	2017-03-20 13:55:58.823983848 +0100
@@ -1149,6 +1149,10 @@ old_insns_match_p (int mode ATTRIBUTE_UN
   else if (p1 || p2)
     return dir_none;
 
+  /* Do not allow cross-jumping frame related insns.  */
+  if (RTX_FRAME_RELATED_P (i1) || RTX_FRAME_RELATED_P (i2))
+    return dir_none;
+
   p1 = PATTERN (i1);
   p2 = PATTERN (i2);
 
--- gcc/testsuite/g++.dg/opt/pr80102.C.jj	2017-03-20 14:34:01.223434828 +0100
+++ gcc/testsuite/g++.dg/opt/pr80102.C	2017-03-20 14:33:36.000000000 +0100
@@ -0,0 +1,14 @@
+// PR target/80102
+// { dg-do compile }
+// { dg-options "-fnon-call-exceptions -Os" }
+// { dg-additional-options "-mminimal-toc" { target { powerpc*-*-* && lp64 } } }
+
+struct B { float a; B (float c) { for (int g; g < c;) ++a; } };
+struct D { D (B); };
+
+int
+main ()
+{
+  B (1.0);
+  D e (0.0), f (1.0);
+}


	Jakub