[Bug libc/206] malloc does not align memory correctly for sse capable systems

["bangerth at ices dot utexas dot edu" <sourceware-bugzilla at sources dot redhat dot com>]

------- Additional Comments From bangerth at ices dot utexas dot edu  2004-06-08 15:41 -------
Subject: Re:  malloc does not align memory correctly for sse capable systems


> MALLOC_ALIGNMENT in glibc is really not going to change, it is a
> quality of implementation, sure, by making it bigger the quality
> implementation would drop a lot for most of the programs out there.

Is it possible to quantify this somehow?


> SSE types are certainly out of the scope of the C standard.  GCC allows to
> create objects with arbitrary alignment, not just __m128, but you can use
> say: __attribute__((aligned (256))).  With the same argumentation, you
> could request that all malloc memory is 256 bytes aligned (or 4K or
> whatever you choose).

That's a reasonable argument indeed. In fact, we would presently simply get 
code that ignores this alignment requirement, we only noticed for SSE types 
since the processor traps when this happens.


> If you want to make C++ new working on these types,

OK, I will go back to the gcc guys with this. Thanks
  Wolfgang

-------------------------------------------------------------------------
Wolfgang Bangerth              email:            bangerth@ices.utexas.edu
                               www: http://www.ices.utexas.edu/~bangerth/



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http://sources.redhat.com/bugzilla/show_bug.cgi?id=206

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