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From: "mikpelinux at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/58779] [4.7/4.8/4.9 Regression] wrong code at -O1 on x86_64-linux-gnu
Date: Sun, 20 Oct 2013 21:08:00 -0000 [thread overview]
Message-ID: <bug-58779-4-4qONlsDVwt@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-58779-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58779
Mikael Pettersson <mikpelinux at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |ktietz at gcc dot gnu.org,
| |mikpelinux at gmail dot com
--- Comment #2 from Mikael Pettersson <mikpelinux at gmail dot com> ---
Started with r180109. CC:ing author.
The code generation difference for this test case at r180109 is:
--- pr58779-r180108.s 2013-10-20 22:44:38.935370903 +0200
+++ pr58779-r180109.s 2013-10-20 22:40:11.576301229 +0200
@@ -8,11 +8,10 @@
subq $8, %rsp
.cfi_def_cfa_offset 16
movl a(%rip), %eax
- leal -1(%rax), %edx
- cmpl %edx, %eax
- jb .L2
+ addl $-1, %eax
+ jb .L3
call abort
-.L2:
+.L3:
movl $0, %eax
addq $8, %rsp
.cfi_def_cfa_offset 8
But these two code fragments set the flags differently: according to gdb the
older one sets CF AF IF at the point of the jb, while the newer one sets PF SF
IF. Since jb checks CF, the newer code fails.
next prev parent reply other threads:[~2013-10-20 21:08 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-18 6:44 [Bug rtl-optimization/58779] New: " su at cs dot ucdavis.edu
2013-10-18 6:53 ` [Bug rtl-optimization/58779] [4.7/4.8/4.9 Regression] " pinskia at gcc dot gnu.org
2013-10-18 8:16 ` rguenth at gcc dot gnu.org
2013-10-20 21:08 ` mikpelinux at gmail dot com [this message]
2013-10-21 6:52 ` [Bug target/58779] " pinskia at gcc dot gnu.org
2013-10-22 6:10 ` ubizjak at gmail dot com
2013-10-22 7:08 ` ubizjak at gmail dot com
2013-10-22 18:36 ` uros at gcc dot gnu.org
2013-10-22 18:38 ` ubizjak at gmail dot com
2013-10-26 6:02 ` uros at gcc dot gnu.org
2013-10-26 6:09 ` uros at gcc dot gnu.org
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