[Bug c/33111] Bad code generation with -O2 (ARM 7 architecture)

[gressau at optusnet dot com dot au]

--- 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=14180action=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).


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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is obsolete||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is obsolete||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is obsolete||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

[Bug c/33111] Bad code generation with -O2 (ARM 7 architecture)

[rask at gcc dot gnu dot org]

--- 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?


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33111

[Bug c/33111] Bad code generation with -O2 (ARM 7 architecture)

[gressau at optusnet dot com dot au]

--- 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:[EMAIL PROTECTED] 
Sent: Monday, 10 September 2007 07:08
To: [EMAIL PROTECTED]
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?


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33111

[Bug c/33111] Bad code generation with -O2 (ARM 7 architecture)

[pinskia at gcc dot gnu dot org]

--- 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.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33111

[Bug c/33111] Bad code generation with -O2 (ARM 7 architecture)

[gressau at optusnet dot com dot au]

--- 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.


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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

[Bug c/33111] Bad code generation with -O2 (ARM 7 architecture)

[gressau at optusnet dot com dot au]

--- 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=14077action=view)
This file does not compile correctly with -O2


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33111

[Bug c/33111] Bad code generation with -O2 (ARM 7 architecture)

[gressau at optusnet dot com dot au]

--- 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=14078action=view)
This is the working unoptimized assembly of uip.c


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33111

[Bug c/33111] Bad code generation with -O2 (ARM 7 architecture)

[gressau at optusnet dot com dot au]

--- 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=14079action=view)
This is the nonworking optimized assembly of uip.c


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33111