[LLVMdev] faster?

Jim Grosbach grosbach at apple.com
Fri Feb 3 11:18:15 PST 2012


Ah, OK. Sorry, I misunderstood the context. Chris covered the other aspect of the question perfectly, so I have nothing to add there.

Cheers!

  Jim


On Feb 3, 2012, at 11:12 AM, Luca Ciciriello <luca_ciciriello at hotmail.com> wrote:

> Ok, thanks Chris.
> Yes, my code not involve the compiler itself. 
> Anyway the Jim advice is useful.
> 
> Thanks again.
> 
> Luca.
> 
> On Feb 3, 2012, at 8:01 PM, Chris Lattner wrote:
> 
>> I don't think he's asking about code in the compiler itself.  In any case, the foreach loop doesn't evaluate "end()" every iteration of the loop.  Depending in what the container is, that could be worse.
>> 
>> My advice is to use the foreach loop and file a bug if you find a case that is ever slower.
>> 
>> -Chris
>> 
>> On Feb 3, 2012, at 10:06 AM, Jim Grosbach <grosbach at apple.com> wrote:
>> 
>>> Hi Luca,
>>> 
>>> Don't use 'auto' in LLVM code for now. We still support building via some host compilers that don't support it.
>>> 
>>> -Jim
>>> 
>>> On Feb 3, 2012, at 7:31 AM, Luca Ciciriello <luca_ciciriello at hotmail.com> wrote:
>>> 
>>>> Hi All.
>>>> 
>>>> In my C++ code I'm using the libc++ library and my question is about which construct is faster:
>>>> 
>>>> for(auto line :  lines)
>>>> {
>>>>  ...
>>>> }
>>>> 
>>>> or
>>>> 
>>>> for(auto it = lines.begin(); it != lines.end(); it++)
>>>> {
>>>>>>>> }
>>>> 
>>>> Thanks in advance for any answer.
>>>> 
>>>> Luca.
>>>> _______________________________________________
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>>>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
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>>> 
>>> 
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>> 
> 





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