[cfe-dev] aligned 'new'

[Anton Yartsev]

On 21.07.2011 0:58, Anton Yartsev wrote:
> On 12.07.2011 1:22, Anton Yartsev wrote:
>> On 24.06.2011 5:43, Anton Yartsev wrote:
>>> On 30.05.2011 8:35, Chris Lattner wrote:
>>>> On May 29, 2011, at 8:49 PM, Anton Yartsev wrote:
>>>>
>>>>> Hi all,
>>>>>
>>>>> I am thinking of the ability of operator new to return memory aligned
>>>>> according to the alignment of the type passed to it (at least of 
>>>>> AltiVec
>>>>> vector types whose proper alignment is essential).
>>>>> The proposed implementation is:
>>>>> 1) clang: add -fstrict-aligned option. When the option is set it 
>>>>> cause
>>>>> clang to define the built-in macro "__STRICT_ALIGNED"
>>>>> 2) libcxx: add additional placement new declarations to
>>>>> libcxx\include\new with the additional argument - alignment. Make 
>>>>> this
>>>>> declarations conditionalized on the "__STRICT_ALIGNED". Add new
>>>>> definitions to libcxx\src\new.cpp.
>>>>> 3) clang: if -fstrict-aligned option is set, when clang sees a new 
>>>>> of a
>>>>> type which either has an inherent alignment, or has an explicit
>>>>> alignment specified by __attribute__((__aligned__(x))), it will
>>>>> transform the standard new call to a call to the aligned version 
>>>>> of new.
>>>>>
>>>>> Am i on the right way? Any thoughts?
>>>> I don't think that this is the right way to go.  Instead, you'd 
>>>> want "new foo" to automatically detect that the alignment of "foo" 
>>>> is greater than the alignment guaranteed by the system malloc.  In 
>>>> this case, and if using the default operator new, you'd generate a 
>>>> call to memalign instead of to operator new (something like that).
>>>>
>>>> It isn't clear to me how generally useful this is though, and we 
>>>> tend to avoid adding tons of language extensions to Clang.
>>>>
>>>> -Chris
>>> Attached is the the patch that substitutes calls to default new 
>>> operators with calls to functions - aligned analogs of default new 
>>> operators. This functions may live in the clang's mm_malloc.h header 
>>> where aligned malloc lives.  The patch is partial, it does not 
>>> affect deletes and do not contain substituting functions yet. Please 
>>> review and direct!
>>>
>> Ping!
>>
> Hi,
>
> here is the updated patch that substitute both news and deletes, 
> please review!
>
Final patch with aligned functions added, please review!

-- 
Anton

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