[llvm-commits] [llvm] r56885 - in /llvm/trunk: include/llvm/Target/TargetLowering.h lib/CodeGen/SelectionDAG/SelectionDAG.cpp lib/Target/X86/X86ISelLowering.cpp lib/Target/X86/X86ISelLowering.h lib/Target/X86/X86Subtarget.cpp lib/Target/X86/X86Su

[Evan Cheng]

So your take is -fno-builtin stops gcc from recognizing memcpy, memset  
as special functions and optimizing them into something else (e.g.  
bzero). After re-reading the man page entry a few times, I kinda see  
it. I wish I can find the code in gcc that does this to have higher  
confidence.

However, this means we should 1) rename -no-builtin to something like - 
no-builtin-optimization, 2) it should disable all of the optimizations  
for memcpy and memset (and probably) others.

Evan

On Sep 30, 2008, at 3:25 PM, Bill Wendling wrote:

>>
>> Before we charge ahead with this, can we take a moment and consider
>> whether it's desireable? This is giving -fno-builtin a significantly
>> different meaning from what it has in GCC.
>>
> I changed it so that it won't convert a memset to a bzero. This should
> be in line with how GCC treats this flag:
>
>           Don't recognize built-in functions that do not begin with
>           __builtin_ as prefix.
>
> -bw
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