From 28623c81b50663e946790649352cb1b3ed23954d Mon Sep 17 00:00:00 2001
From: Max Filippov <jcmvbkbc@gmail.com>
Date: Tue, 24 Sep 2019 04:15:17 -0700
Subject: [PATCH] xtensa: fix PR target/91880

Xtensa hwloop_optimize segfaults when zero overhead loop is about to be
inserted as the first instruction of the function.
Insert zero overhead loop instruction into new basic block before the
loop when basic block that precedes the loop is empty.

2019-09-26  Max Filippov  <jcmvbkbc@gmail.com>
gcc/
	* config/xtensa/xtensa.c (hwloop_optimize): Insert zero overhead
	loop instruction into new basic block before the loop when basic
	block that precedes the loop is empty.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
[Romain: rebase on gcc 8.4.0]
Signed-off-by: Romain Naour <romain.naour@smile.fr>
---
Backported from: r276166

 gcc/config/xtensa/xtensa.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/gcc/config/xtensa/xtensa.c b/gcc/config/xtensa/xtensa.c
index 08f9f7c7a8f..de206527810 100644
--- a/gcc/config/xtensa/xtensa.c
+++ b/gcc/config/xtensa/xtensa.c
@@ -4232,7 +4232,9 @@ hwloop_optimize (hwloop_info loop)
 
   seq = get_insns ();
 
-  if (!single_succ_p (entry_bb) || vec_safe_length (loop->incoming) > 1)
+  entry_after = BB_END (entry_bb);
+  if (!single_succ_p (entry_bb) || vec_safe_length (loop->incoming) > 1
+      || !entry_after)
     {
       basic_block new_bb;
       edge e;
@@ -4253,7 +4255,6 @@ hwloop_optimize (hwloop_info loop)
     }
   else
     {
-      entry_after = BB_END (entry_bb);
       while (DEBUG_INSN_P (entry_after)
              || (NOTE_P (entry_after)
 		 && NOTE_KIND (entry_after) != NOTE_INSN_BASIC_BLOCK))
-- 
2.24.1