OBS-URL: https://build.opensuse.org/package/show/devel:gcc/gcc13?expand=0&rev=103

gcc13-pr101523.patch

@@ -1,48 +1,46 @@
-From 839bc42772ba7af66af3bd16efed4a69511312ae Mon Sep 17 00:00:00 2001
-From: Segher Boessenkool <segher@kernel.crashing.org>
-Date: Wed, 27 Mar 2024 14:09:52 +0000
-Subject: [PATCH] combine: Don't combine if I2 does not change
+From 5729ffad4db78b26f0d1f658a9fd695be5970550 Mon Sep 17 00:00:00 2001
+From: Richard Biener <rguenther@suse.de>
+Date: Wed, 3 Apr 2024 12:58:26 +0200
+Subject: [PATCH] rtl-optimization/101523 - avoid re-combine after noop 2->2
+ combination
 To: gcc-patches@gcc.gnu.org
 
-In some cases combine will "combine" an I2 and I3, but end up putting
-exactly the same thing back as I2 as was there before.  This is never
-progress, so we shouldn't do it, it will lead to oscillating behaviour
-and the like.
-
-If we want to canonicalise things, that's fine, but this is not the
-way to do it.
-
-2024-03-27  Segher Boessenkool  <segher@kernel.crashing.org>
+The following avoids re-walking and re-combining the instructions
+between i2 and i3 when the pattern of i2 doesn't change.
 
 	PR rtl-optimization/101523
-	* combine.cc (try_combine): Don't do a 2-insn combination if
-	it does not in fact change I2.
+	* combine.cc (try_combine): When the pattern of i2 doesn't
+	change do not re-start combining at i2 or an earlier insn which
+	had links or notes added.
 ---
- gcc/combine.cc | 11 +++++++++++
- 1 file changed, 11 insertions(+)
+ gcc/combine.cc | 7 +++++++
+ 1 file changed, 7 insertions(+)
 
 diff --git a/gcc/combine.cc b/gcc/combine.cc
-index a4479f8d836..745391016d0 100644
+index a4479f8d836..ff25752cac4 100644
 --- a/gcc/combine.cc
 +++ b/gcc/combine.cc
-@@ -4186,6 +4186,17 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1, rtx_insn *i0,
+@@ -4186,6 +4186,10 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1, rtx_insn *i0,
        adjust_for_new_dest (i3);
      }
  
-+  /* If I2 didn't change, this is not a combination (but a simplification or
-+     canonicalisation with context), which should not be done here.  Doing
-+     it here explodes the algorithm.  Don't.  */
++  bool i2_unchanged = false;
 +  if (rtx_equal_p (newi2pat, PATTERN (i2)))
-+    {
-+      if (dump_file)
-+	fprintf (dump_file, "i2 didn't change, not doing this\n");
-+      undo_all ();
-+      return 0;
-+    }
++    i2_unchanged = true;
 +
    /* We now know that we can do this combination.  Merge the insns and
       update the status of registers and LOG_LINKS.  */
  
+@@ -4752,6 +4756,9 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1, rtx_insn *i0,
+   combine_successes++;
+   undo_commit ();
+ 
++  if (i2_unchanged)
++    return i3;
++
+   rtx_insn *ret = newi2pat ? i2 : i3;
+   if (added_links_insn && DF_INSN_LUID (added_links_insn) < DF_INSN_LUID (ret))
+     ret = added_links_insn;
 -- 
 2.35.3
 

gcc13.changes

@@ -1,5 +1,5 @@
 -------------------------------------------------------------------
-Thu Mar 28 06:55:18 UTC 2024 - Richard Biener <rguenther@suse.com>
+Thu Apr  4 07:43:17 UTC 2024 - Richard Biener <rguenther@suse.com>
 
 - Add gcc13-pr101523.patch to avoid combine spending too much
   compile-time and memory doing nothing on s390x.  [boo#1188441]