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From: "mikpe at it dot uu dot se" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/44328] switch/case optimization produces an invalid jump table index
Date: Sun, 30 May 2010 14:50:00 -0000 [thread overview]
Message-ID: <20100530145025.20689.qmail@sourceware.org> (raw)
In-Reply-To: <bug-44328-19252@http.gcc.gnu.org/bugzilla/>
------- Comment #2 from mikpe at it dot uu dot se 2010-05-30 14:50 -------
I can confirm this wrong-code when gcc 4.4/4.5 targets arm-unknown-eabi.
However, a 4.4/4.5 running natively on arm-unknown-linux-gnueabi does not
exhibit this behaviour. There there's no 'comparison always true' warning, and
the generated code contains conditional instructions where the arm-unknown-eabi
gcc emitted unconditional instructions.
This is what 4.5-20100527 generates for me on arm-unknown-linux-gnueabi:
sub r1, r1, #1
cmp r1, #2
ldrls r3, .L4
movhi r1, #1
ldrls r1, [r3, r1, asl #2]
b open
.L5:
.align 2
.L4:
.word .LANCHOR0
.size _Z9open_filePKc8OpenMode, .-_Z9open_filePKc8OpenMode
.section .rodata
.align 2
.LANCHOR0 = . + 0
.type CSWTCH.2, %object
.size CSWTCH.2, 12
CSWTCH.2:
.word 74
.word 3
.word 75
My guess is that the subtract+compare is done in a too narrow mode, resulting
in the warning and subsequent omission of the conditionals.
Also, it's not a jump table but a lookup table.
--
mikpe at it dot uu dot se changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |mikpe at it dot uu dot se
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44328
next prev parent reply other threads:[~2010-05-30 14:50 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-30 0:00 [Bug c++/44328] New: " eblot dot ml at gmail dot com
2010-05-30 10:36 ` [Bug c++/44328] " eblot dot ml at gmail dot com
2010-05-30 14:50 ` mikpe at it dot uu dot se [this message]
2010-05-30 17:36 ` eblot dot ml at gmail dot com
2010-06-04 23:41 ` [Bug c++/44328] switch/case optimization produces an invalid lookup " eblot dot ml at gmail dot com
2010-06-15 15:09 ` jamborm at gcc dot gnu dot org
2010-06-17 9:21 ` eblot dot ml at gmail dot com
2010-06-17 9:37 ` Andrew Pinski
2010-06-17 9:34 ` eblot dot ml at gmail dot com
2010-06-17 9:37 ` pinskia at gmail dot com
2010-06-17 14:02 ` jamborm at gcc dot gnu dot org
2010-06-17 15:01 ` jamborm at gcc dot gnu dot org
2010-06-17 16:34 ` eblot dot ml at gmail dot com
2010-06-17 16:37 ` jamborm at gcc dot gnu dot org
2010-06-17 16:41 ` eblot dot ml at gmail dot com
2010-06-20 13:53 ` eblot dot ml at gmail dot com
2010-06-20 16:51 ` jamborm at gcc dot gnu dot org
2010-06-20 16:57 ` eblot dot ml at gmail dot com
2010-06-20 17:03 ` eblot dot ml at gmail dot com
2010-06-20 18:26 ` mikpe at it dot uu dot se
2010-06-21 8:29 ` jamborm at gcc dot gnu dot org
2010-06-21 10:45 ` mikpe at it dot uu dot se
2010-06-21 11:18 ` mikpe at it dot uu dot se
2010-07-05 13:43 ` [Bug tree-optimization/44328] " ramana at gcc dot gnu dot org
2010-07-24 22:24 ` jifl-bugzilla at jifvik dot org
2010-08-02 12:24 ` ian dot bolton at arm dot com
2010-08-02 13:33 ` ian dot bolton at arm dot com
2010-08-03 17:09 ` ian dot bolton at arm dot com
2010-09-01 11:10 ` jamborm at gcc dot gnu dot org
2010-09-01 11:23 ` jamborm at gcc dot gnu dot org
2010-09-01 11:24 ` jamborm at gcc dot gnu dot org
2010-09-01 11:25 ` ibolton at gcc dot gnu dot org
2010-09-01 11:33 ` jamborm at gcc dot gnu dot org
2010-09-01 11:47 ` jifl-bugzilla at jifvik dot org
2010-09-01 11:50 ` jakub at gcc dot gnu dot org
2010-09-02 13:10 ` ibolton at gcc dot gnu dot org
2010-09-07 9:28 ` ibolton at gcc dot gnu dot org
2010-09-09 15:37 ` ibolton at gcc dot gnu dot org
2010-09-09 15:38 ` rguenth at gcc dot gnu dot org
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