[llvm-commits] [llvm] r120974 - in /llvm/trunk: include/llvm/Analysis/AliasAnalysis.h lib/Transforms/Scalar/DeadStoreElimination.cpp test/Transforms/DeadStoreElimination/simple.ll

[Chris Lattner]

On Dec 6, 2010, at 9:36 AM, Duncan Sands wrote:

>>   // memcpy is not defined if the source and destination pointers are exactly
>>   // equal, but other compilers do this optimization, and almost every memcpy
>>   // implementation handles this case safely.  If there is a libc that does not
>>   // safely handle this, we can add a target hook.
>> 
>> Note that the example from the PR doesn't explicitly call memcpy.
> 
> I've been told that on some platforms zeroing the target memory before doing the
> copy speeds it up due to cache effects.  It looks like clang's implementation
> of struct copy will not work on such targets.

GCC also uses memcpy.  If we find one of these theoretical platforms, clang can always generate memmove on it.

-Chris