sys-devel/gcc: fix SLP returns_twice issue for 13

This fixes a checking (which we now do by default for pre-releases) ICE
for busybox/xdvik, but it's potentially more serious anyway.

Bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109469
Signed-off-by: Sam James <sam@gentoo.org>

1 files changed, 66 insertions, 0 deletions

diff --git a/sys-devel/gcc/files/gcc-13.0.1_pre20230409-PR109469-SLP-returns-twice.patch b/sys-devel/gcc/files/gcc-13.0.1_pre20230409-PR109469-SLP-returns-twice.patch
new file mode 100644
index 000000000000..7d45c9e60af8
--- /dev/null
+++ b/sys-devel/gcc/files/gcc-13.0.1_pre20230409-PR109469-SLP-returns-twice.patch
@@ -0,0 +1,66 @@
+https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109469
+https://gcc.gnu.org/git/gitweb.cgi?p=gcc.git;h=2d7ad38707e1fd71193d440198cc0726092b9015
+
+From 2d7ad38707e1fd71193d440198cc0726092b9015 Mon Sep 17 00:00:00 2001
+From: Richard Biener <rguenther@suse.de>
+Date: Tue, 11 Apr 2023 16:06:12 +0200
+Subject: [PATCH] tree-optimization/109469 - SLP with returns-twice region
+ start
+
+The following avoids an SLP region starting with a returns-twice
+call where we cannot insert stmts at the head.
+
+	PR tree-optimization/109469
+	* tree-vect-slp.cc (vect_slp_function): Skip region starts with
+	a returns-twice call.
+
+	* gcc.dg/torture/pr109469.c: New testcase.
+--- /dev/null
++++ b/gcc/testsuite/gcc.dg/torture/pr109469.c
+@@ -0,0 +1,15 @@
++/* { dg-do compile } */
++
++__attribute__((returns_twice)) int foo();
++
++struct xio myproc;
++struct xio {
++  void (*read_proc)();
++  void (*write_proc)();
++};
++
++void dummy_write_proc() {
++  switch (foo())
++  default:
++    myproc.read_proc = myproc.write_proc = dummy_write_proc;
++}
+--- a/gcc/tree-vect-slp.cc
++++ b/gcc/tree-vect-slp.cc
+@@ -7671,10 +7671,23 @@ vect_slp_function (function *fun)
+ 	{
+ 	  r |= vect_slp_bbs (bbs, NULL);
+ 	  bbs.truncate (0);
+-	  bbs.quick_push (bb);
+ 	}
+-      else
+-	bbs.safe_push (bb);
++
++      /* We need to be able to insert at the head of the region which
++	 we cannot for region starting with a returns-twice call.  */
++      if (bbs.is_empty ())
++	if (gcall *first = safe_dyn_cast <gcall *> (first_stmt (bb)))
++	  if (gimple_call_flags (first) & ECF_RETURNS_TWICE)
++	    {
++	      if (dump_enabled_p ())
++		dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
++				 "skipping bb%d as start of region as it "
++				 "starts with returns-twice call\n",
++				 bb->index);
++	      continue;
++	    }
++
++      bbs.safe_push (bb);
+ 
+       /* When we have a stmt ending this block and defining a
+ 	 value we have to insert on edges when inserting after it for
+-- 
+2.31.1