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Re: [RFC PATCH] add auto_bitmap


Jeff Law <law@redhat.com> wrote:
>On 11/14/13 04:04, tsaunders@mozilla.com wrote:
>> From: Trevor Saunders <tsaunders@mozilla.com>
>>
>> Hi,
>>
>> this patch adds and starts to use a class auto_bitmap, which is a
>very thin
>> wrapper around bitmap.  Its advantage is that it takes care of
>delocation
>> automatically.  So you can do things like
>>
>> int
>> f ()
>> {
>>    auto_bitmap x;
>>    // do stuff with x
>> }
>>
>> Another advantage of this class is it puts the bitmap_head struct on
>the stack
>> instead of mallocing it or using a obstack.
>>
>> I Think the biggest question is if I should make auto_bitmap a full
>c++ified
>> wrapper around   bitmap or if I should contiune just taking the
>address of it
>> and passing it as a bitmap, but other comments are of course welcome
>too.
>I'd prefer to see it fully c++ified.
>
>In response to one of Richi's comments, I spot checked the patch and 
>only found two occurrences where this lengthened the lifetime of the 
>bitmap in any significant way.  The vast majority of the time any 
>increase in length was trivial.
>
>Those instances are in tree-ssa-loop-ivopts.c and the other in 
>tree-ssa-strlen.c.  I don't think you need to change anything for them,
>
>I'm just pointed out that of all the stuff you changed, these were the 
>only ones I saw where lifetimes were changed significantly.

I still ask why we need a new type and cannot put this functionality into bitmap_head itself.

Richard.

>jeff



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