If it is Adjust_Alignment that is causing this problem, and this is for kernel
compilation, why don’t we just use an option like �COPT:space to force the
smaller alignment, which kernel compiles could use?
From: Jian-Xin Lai [mailto:laij...@gmail.com]
Sent: Wednesday, August 24, 2011 9:33 PM
To: Mike Murphy
Cc: Sun Chan; 朱庆; open64-devel@lists.sourceforge.net
Subject: Re: [Open64-devel] Code Review request for bug832[wgen]
This case comes from kernel. It requires a strict alignment for the data.
In Adjust_Alignment, we trend to increase the alignment (for example, to 16
byte) for better performance. Usually, it is OK. But if the code specifies a
special alignment like this example, we need to follow it.
在 2011年8月25日 下午12:28，Mike Murphy
<mmur...@nvidia.com<mailto:mmur...@nvidia.com>>写道：
The alignment is stored in the ty_idx (see TY_align), and then there are
routines like Adjusted_Alignment in stblock that can modify it. I suspect the
problem here is that the alignment is being put on the object rather than the
type, and then is lost (but should still be possible, because the TY_align is
like qualifiers that can vary from the base type). Does the alignment show up
properly in the intermediate .B file?
-----Original Message-----
From: Sun Chan [mailto:sun.c...@gmail.com<mailto:sun.c...@gmail.com>]
Sent: Wednesday, August 24, 2011 7:51 PM
To: 朱庆
Cc:
open64-devel@lists.sourceforge.net<mailto:open64-devel@lists.sourceforge.net>
Subject: Re: [Open64-devel] Code Review request for bug832[wgen]
The reason I asked for the file is that I think there has to be some
alignment attribute somewhere. I am sure data alignment has been dealt
with in the compiler. That it is due to user, or just language
attribute might be irrelevant from compiler point of view.
Mike or Murthy,
Do you remember where alignment is handled? I only found Alignment
field in BLK of the symtab_defs.h
Sun
2011/8/25 朱庆 <zqing1...@gmail.com<mailto:zqing1...@gmail.com>>:
> Hi Sun,
>
> Attached symtab_defs.h.
>
> Thanks
> zhuqing
> 2011/8/24 Sun Chan <sun.c...@gmail.com<mailto:sun.c...@gmail.com>>:
>> can you send me the full symtab_defs.h?
>> Sun
>>
>> On Wed, Aug 24, 2011 at 4:56 PM, 朱庆
>> <zqing1...@gmail.com<mailto:zqing1...@gmail.com>> wrote:
>>> Hi all,
>>>
>>> Can gatekeeper help review following fix for bug832?
>>> https://bugs.open64.net/show_bug.cgi?id=832
>>>
>>> small case, a.c:
>>> struct obs_kernel_param {
>>> const char *str;
>>> };
>>>
>>> const char str1[] = "acpi_parse_apic_instance=";
>>> const char str2[] = "acpi_os_name";
>>> struct obs_kernel_param var1
>>> __attribute__ ((aligned ((sizeof (long))))) =
>>> {str1};
>>>
>>> struct obs_kernel_param var2
>>> __attribute__ ((aligned ((sizeof (long))))) =
>>> {str2};
>>>
>>> when compile with opencc, nm a.o
>>> 0000000000000000 D var1
>>> 0000000000000010 D var2
>>> compile with gcc, nm a.o
>>> 0000000000000000 D var1
>>> 0000000000000008 D var2
>>> the offset of var1 and var2 are different, the problem with opencc is
>>> :fixed align attribute does not work, this may cause some problems
>>> when mix link two files with opencc and gcc.
>>>
>>> The fix is to add a new ST flag to record user_defined_align.
>>>
>>> Thanks
>>> zhuqing
>>>
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>>>
>>
>
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