llvm dev - Dec 2009 - [LLVMdev] detailed comparison of generated code size for LLVM and other compilers

On Dec 14, 2009, at 9:46 AMPST, Chris Lattner wrote:
>
> On Dec 14, 2009, at 7:33 AM, John Regehr wrote:
>
>> See here:
>>
>>  http://embed.cs.utah.edu/embarrassing/
>>
>> There is a lot of data there.  Please excuse bugs and other problems.
>> Feedback would be appreciated.
>
> Hi John,
>
> I agree with the gcc folks: it's really important to get frame pointer
> emission etc aligned across the various compilers.  ICC defaulting to
> frame pointers off and GCC/llvm defaulting to them on will seriously
> warp the numbers.
Where did the gcc folks express this opinion?

There are probably other differing defaults besides frame pointers.   
Stack protectors, perhaps.

On Dec 14, 2009, at 11:04 AM, Dale Johannesen wrote:
>>
>> I agree with the gcc folks: it's really important to get frame  
>> pointer
>> emission etc aligned across the various compilers.  ICC defaulting to
>> frame pointers off and GCC/llvm defaulting to them on will seriously
>> warp the numbers.
>
> Where did the gcc folks express this opinion?
The GCC mailing list.
> There are probably other differing defaults besides frame pointers.   
> Stack protectors, perhaps.
Yes, that's another good example,

-Chris

>> There are probably other differing defaults besides frame pointers. 
Stack
>> protectors, perhaps.
>
> Yes, that's another good example,
Ok-- I assume I should just add '-fno-stack-protector' to the llvm-gcc
and
clang command lines?  I had totally missed that something like this was 
turned on by default.

I'll re-run everything with this change, with frame pointers omitted, and 
dropping testcases that contain uses of uninititalized locals and post 
here again when that's done.

Thanks for the feedback,

John