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* [Bug c/33111] New: Bad code generation with -O2 (ARM 7 architecture)
@ 2007-08-19 7:49 gressau at optusnet dot com dot au
2007-08-19 8:59 ` [Bug c/33111] " pinskia at gcc dot gnu dot org
` (9 more replies)
0 siblings, 10 replies; 11+ messages in thread
From: gressau at optusnet dot com dot au @ 2007-08-19 7:49 UTC (permalink / raw)
To: gcc-bugs
#define UIP_LLH_LEN 10000
#define BUF ((uip_tcpip_hdr *)&uip_buf[UIP_LLH_LEN])
#define u8_t unsigned char
#define u16_t unsigned short
#define UIP_BUFSIZE 1000
typedef struct {
/* IP header. */
u8_t vhl,
tos,
len[2],
ipid[2],
ipoffset[2],
ttl,
proto;
u16_t ipchksum;
u16_t srcipaddr[2],
destipaddr[2];
/* TCP header. */
u16_t srcport,
destport;
u8_t seqno[4],
ackno[4],
tcpoffset,
flags,
wnd[2];
u16_t tcpchksum;
u8_t urgp[2];
u8_t optdata[4];
} uip_tcpip_hdr;
u8_t uip_buf[UIP_BUFSIZE+2];
volatile u8_t uip_acc32[4];
int jaroslav;
int main(void)
{
if((BUF->ackno[0] == uip_acc32[0]) &&
(BUF->ackno[1] == uip_acc32[1]) &&
(BUF->ackno[2] == uip_acc32[2]) &&
(BUF->ackno[3] == uip_acc32[3]))
jaroslav++;
return 1;
}
.file "main.c"
.text
.align 2
.global main
.type main, %function
main:
@ args = 0, pretend = 0, frame = 0
@ frame_needed = 0, uses_anonymous_args = 0
@ link register save eliminated.
ldr r0, .L10
ldr r1, .L10+4
ldrb r2, [r0, #28] @ zero_extendqisi2
ldrb r3, [r1, #0] @ zero_extendqisi2
cmp r2, r3
@ lr needed for prologue
beq .L9
.L2:
mov r0, #1
bx lr
.L9:
ldrb r2, [r1, #1] @ zero_extendqisi2
ldrb r3, [r0, #29] @ zero_extendqisi2
cmp r3, r2
bne .L2
ldrb r2, [r1, #2] @ zero_extendqisi2
ldrb r3, [r0, #30] @ zero_extendqisi2
cmp r3, r2
bne .L2
ldrb r2, [r1, #3] @ zero_extendqisi2
ldrb r3, [r0, #31] @ zero_extendqisi2
cmp r3, r2 !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!I THINK CC's OF THIS
COMPARE NEVER GET LOOKED AT
ldreq r2, .L10+8
ldreq r3, [r2, #0]
addeq r3, r3, #1
streq r3, [r2, #0]
b .L2
.L11:
.align 2
.L10:
.word uip_buf+10000
.word uip_acc32
.word jaroslav
.size main, .-main
.comm uip_buf,1002,1
.comm uip_acc32,4,1
.comm jaroslav,4,4
.ident "GCC: (GNU) 4.2.0"
--
Summary: Bad code generation with -O2 (ARM 7 architecture)
Product: gcc
Version: 4.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: gressau at optusnet dot com dot au
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33111
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug c/33111] Bad code generation with -O2 (ARM 7 architecture)
2007-08-19 7:49 [Bug c/33111] New: Bad code generation with -O2 (ARM 7 architecture) gressau at optusnet dot com dot au
@ 2007-08-19 8:59 ` pinskia at gcc dot gnu dot org
2007-08-19 13:24 ` gressau at optusnet dot com dot au
` (8 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2007-08-19 8:59 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from pinskia at gcc dot gnu dot org 2007-08-19 08:59 -------
> #define BUF ((uip_tcpip_hdr *)&uip_buf[UIP_LLH_LEN])
Right there is an alias violation.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33111
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug c/33111] Bad code generation with -O2 (ARM 7 architecture)
2007-08-19 7:49 [Bug c/33111] New: Bad code generation with -O2 (ARM 7 architecture) gressau at optusnet dot com dot au
2007-08-19 8:59 ` [Bug c/33111] " pinskia at gcc dot gnu dot org
@ 2007-08-19 13:24 ` gressau at optusnet dot com dot au
2007-08-19 22:23 ` gressau at optusnet dot com dot au
` (7 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: gressau at optusnet dot com dot au @ 2007-08-19 13:24 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from gressau at optusnet dot com dot au 2007-08-19 13:23 -------
The attached sample code does not illustrate the real problem.
Further investigation is required why the code works with -O0
and does not work with -O2.
--
gressau at optusnet dot com dot au changed:
What |Removed |Added
----------------------------------------------------------------------------
CC|gressau at optusnet dot com |
|dot au |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33111
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug c/33111] Bad code generation with -O2 (ARM 7 architecture)
2007-08-19 7:49 [Bug c/33111] New: Bad code generation with -O2 (ARM 7 architecture) gressau at optusnet dot com dot au
2007-08-19 8:59 ` [Bug c/33111] " pinskia at gcc dot gnu dot org
2007-08-19 13:24 ` gressau at optusnet dot com dot au
@ 2007-08-19 22:23 ` gressau at optusnet dot com dot au
2007-08-19 22:24 ` gressau at optusnet dot com dot au
` (6 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: gressau at optusnet dot com dot au @ 2007-08-19 22:23 UTC (permalink / raw)
To: gcc-bugs
------- Comment #3 from gressau at optusnet dot com dot au 2007-08-19 22:22 -------
Created an attachment (id=14077)
--> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=14077&action=view)
This file does not compile correctly with -O2
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33111
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug c/33111] Bad code generation with -O2 (ARM 7 architecture)
2007-08-19 7:49 [Bug c/33111] New: Bad code generation with -O2 (ARM 7 architecture) gressau at optusnet dot com dot au
` (2 preceding siblings ...)
2007-08-19 22:23 ` gressau at optusnet dot com dot au
@ 2007-08-19 22:24 ` gressau at optusnet dot com dot au
2007-08-19 22:25 ` gressau at optusnet dot com dot au
` (5 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: gressau at optusnet dot com dot au @ 2007-08-19 22:24 UTC (permalink / raw)
To: gcc-bugs
------- Comment #4 from gressau at optusnet dot com dot au 2007-08-19 22:24 -------
Created an attachment (id=14078)
--> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=14078&action=view)
This is the working unoptimized assembly of uip.c
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33111
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug c/33111] Bad code generation with -O2 (ARM 7 architecture)
2007-08-19 7:49 [Bug c/33111] New: Bad code generation with -O2 (ARM 7 architecture) gressau at optusnet dot com dot au
` (3 preceding siblings ...)
2007-08-19 22:24 ` gressau at optusnet dot com dot au
@ 2007-08-19 22:25 ` gressau at optusnet dot com dot au
2007-09-09 20:44 ` gressau at optusnet dot com dot au
` (4 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: gressau at optusnet dot com dot au @ 2007-08-19 22:25 UTC (permalink / raw)
To: gcc-bugs
------- Comment #5 from gressau at optusnet dot com dot au 2007-08-19 22:25 -------
Created an attachment (id=14079)
--> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=14079&action=view)
This is the nonworking optimized assembly of uip.c
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33111
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug c/33111] Bad code generation with -O2 (ARM 7 architecture)
2007-08-19 7:49 [Bug c/33111] New: Bad code generation with -O2 (ARM 7 architecture) gressau at optusnet dot com dot au
` (4 preceding siblings ...)
2007-08-19 22:25 ` gressau at optusnet dot com dot au
@ 2007-09-09 20:44 ` gressau at optusnet dot com dot au
2007-09-09 21:08 ` rask at gcc dot gnu dot org
` (3 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: gressau at optusnet dot com dot au @ 2007-09-09 20:44 UTC (permalink / raw)
To: gcc-bugs
------- Comment #6 from gressau at optusnet dot com dot au 2007-09-09 20:44 -------
Created an attachment (id=14180)
--> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=14180&action=view)
Test of optimized comparison (-O2)
Comparison of four consecutive bytes gets optimized (-O2) as comparison of a
word. The word address produced does not have the last two bits zero and the
ARM7 processor either ignores them (LPC2000) or data aborts (SAM7).
--
gressau at optusnet dot com dot au changed:
What |Removed |Added
----------------------------------------------------------------------------
Attachment #14077|0 |1
is obsolete| |
Attachment #14078|0 |1
is obsolete| |
Attachment #14079|0 |1
is obsolete| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33111
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug c/33111] Bad code generation with -O2 (ARM 7 architecture)
2007-08-19 7:49 [Bug c/33111] New: Bad code generation with -O2 (ARM 7 architecture) gressau at optusnet dot com dot au
` (5 preceding siblings ...)
2007-09-09 20:44 ` gressau at optusnet dot com dot au
@ 2007-09-09 21:08 ` rask at gcc dot gnu dot org
2007-09-09 22:23 ` gressau at optusnet dot com dot au
` (2 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: rask at gcc dot gnu dot org @ 2007-09-09 21:08 UTC (permalink / raw)
To: gcc-bugs
------- Comment #7 from rask at gcc dot gnu dot org 2007-09-09 21:08 -------
Did you read comment #1?
Does -fno-strict-aliasing magically "fix" your code?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33111
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug c/33111] Bad code generation with -O2 (ARM 7 architecture)
2007-08-19 7:49 [Bug c/33111] New: Bad code generation with -O2 (ARM 7 architecture) gressau at optusnet dot com dot au
` (6 preceding siblings ...)
2007-09-09 21:08 ` rask at gcc dot gnu dot org
@ 2007-09-09 22:23 ` gressau at optusnet dot com dot au
2008-12-27 6:54 ` [Bug target/33111] " pinskia at gcc dot gnu dot org
2009-05-22 14:51 ` rearnsha at gcc dot gnu dot org
9 siblings, 0 replies; 11+ messages in thread
From: gressau at optusnet dot com dot au @ 2007-09-09 22:23 UTC (permalink / raw)
To: gcc-bugs
------- Comment #8 from gressau at optusnet dot com dot au 2007-09-09 22:23 -------
Subject: RE: Bad code generation with -O2 (ARM 7 architecture)
The -fno-strict-aliasing does not fix the unaligned access.
-----Original Message-----
From: rask at gcc dot gnu dot org [mailto:gcc-bugzilla@gcc.gnu.org]
Sent: Monday, 10 September 2007 07:08
To: gressau@optusnet.com.au
Subject: [Bug c/33111] Bad code generation with -O2 (ARM 7 architecture)
------- Comment #7 from rask at gcc dot gnu dot org 2007-09-09 21:08
-------
Did you read comment #1?
Does -fno-strict-aliasing magically "fix" your code?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33111
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug target/33111] Bad code generation with -O2 (ARM 7 architecture)
2007-08-19 7:49 [Bug c/33111] New: Bad code generation with -O2 (ARM 7 architecture) gressau at optusnet dot com dot au
` (7 preceding siblings ...)
2007-09-09 22:23 ` gressau at optusnet dot com dot au
@ 2008-12-27 6:54 ` pinskia at gcc dot gnu dot org
2009-05-22 14:51 ` rearnsha at gcc dot gnu dot org
9 siblings, 0 replies; 11+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2008-12-27 6:54 UTC (permalink / raw)
To: gcc-bugs
------- Comment #9 from pinskia at gcc dot gnu dot org 2008-12-27 06:53 -------
(In reply to comment #1)
> > #define BUF ((uip_tcpip_hdr *)&uip_buf[UIP_LLH_LEN])
> Right there is an alias violation.
More than that this is an alignment violation.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33111
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug target/33111] Bad code generation with -O2 (ARM 7 architecture)
2007-08-19 7:49 [Bug c/33111] New: Bad code generation with -O2 (ARM 7 architecture) gressau at optusnet dot com dot au
` (8 preceding siblings ...)
2008-12-27 6:54 ` [Bug target/33111] " pinskia at gcc dot gnu dot org
@ 2009-05-22 14:51 ` rearnsha at gcc dot gnu dot org
9 siblings, 0 replies; 11+ messages in thread
From: rearnsha at gcc dot gnu dot org @ 2009-05-22 14:51 UTC (permalink / raw)
To: gcc-bugs
------- Comment #10 from rearnsha at gcc dot gnu dot org 2009-05-22 14:51 -------
The ARM7 does not support unaligned accesses in the way that C programmers
normally expect (even if it doesn't fault them in the MMU then it still won't
fetch what you might expect -- see the CPU manuals for details).
As of ARM11 the rules were changed, but that's a different story...
--
rearnsha at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution| |INVALID
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33111
^ permalink raw reply [flat|nested] 11+ messages in thread
end of thread, other threads:[~2009-05-22 14:51 UTC | newest]
Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed)
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2007-08-19 7:49 [Bug c/33111] New: Bad code generation with -O2 (ARM 7 architecture) gressau at optusnet dot com dot au
2007-08-19 8:59 ` [Bug c/33111] " pinskia at gcc dot gnu dot org
2007-08-19 13:24 ` gressau at optusnet dot com dot au
2007-08-19 22:23 ` gressau at optusnet dot com dot au
2007-08-19 22:24 ` gressau at optusnet dot com dot au
2007-08-19 22:25 ` gressau at optusnet dot com dot au
2007-09-09 20:44 ` gressau at optusnet dot com dot au
2007-09-09 21:08 ` rask at gcc dot gnu dot org
2007-09-09 22:23 ` gressau at optusnet dot com dot au
2008-12-27 6:54 ` [Bug target/33111] " pinskia at gcc dot gnu dot org
2009-05-22 14:51 ` rearnsha at gcc dot gnu dot org
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