From d4c03c1e41043f25e21889762bceb480abb56634 Mon Sep 17 00:00:00 2001
From: Matheus Tavares Bernardino <quic_mathbern@quicinc.com>
Date: Mon, 13 Mar 2023 15:58:19 -0300
Subject: [PATCH] migration/xbzrle: use ctz64 to avoid undefined result

mainline inclusion
from mainline-v8.0.0-rc1
commit d84a78d15d3af9ff28ceec6906a4b101bd545b55
category: feature
feature: AVX512 support for xbzrle_encode_buffer
bugzilla: https://gitee.com/openeuler/intel-qemu/issues/I6Z50P

Intel-SIG: commit d84a78d15d3a ("migration/xbzrle: use ctz64 to avoid undefined result")

-------------------------------------

migration/xbzrle: use ctz64 to avoid undefined result

__builtin_ctzll() produces undefined results when the argument is 0.
This can be seen through test-xbzrle, which produces the following
warning:

../migration/xbzrle.c:265: runtime error: passing zero to ctz(), which is not a valid argument

Replace __builtin_ctzll() with our ctz64() wrapper which properly
handles 0.

Signed-off-by: Matheus Tavares Bernardino <quic_mathbern@quicinc.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Aichun Shi <aichun.shi@intel.com>
---
 migration/xbzrle.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/migration/xbzrle.c b/migration/xbzrle.c
index 05366e86c0..21b92d4eae 100644
--- a/migration/xbzrle.c
+++ b/migration/xbzrle.c
@@ -12,6 +12,7 @@
  */
 #include "qemu/osdep.h"
 #include "qemu/cutils.h"
+#include "qemu/host-utils.h"
 #include "xbzrle.h"
 
 /*
@@ -233,7 +234,7 @@ int xbzrle_encode_buffer_avx512(uint8_t *old_buf, uint8_t *new_buf, int slen,
                     break;
                 }
                 never_same = false;
-                num = __builtin_ctzll(~comp);
+                num = ctz64(~comp);
                 num = (num < bytes_to_check) ? num : bytes_to_check;
                 zrun_len += num;
                 bytes_to_check -= num;
@@ -262,7 +263,7 @@ int xbzrle_encode_buffer_avx512(uint8_t *old_buf, uint8_t *new_buf, int slen,
                 nzrun_len += 64;
                 break;
             }
-            num = __builtin_ctzll(comp);
+            num = ctz64(comp);
             num = (num < bytes_to_check) ? num : bytes_to_check;
             nzrun_len += num;
             bytes_to_check -= num;
-- 
2.27.0