[LLVMdev] detailed comparison of generated code size for LLVM and other compilers

Dale Johannesen dalej at apple.com
Mon Dec 14 13:27:03 PST 2009

On Dec 14, 2009, at 12:23 PMPST, John Regehr wrote:

>>> 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.

You'll probably need to  some digging to make sure the defaults are  
exactly comparable.  Are SSE and/or MMX used?  This affects floating  
point codegen quite a bit.  Are the target CPUs the same?

I think some useful information is going to come out of this, but  
there's some cruft to clear out first.

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