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Re: Builtin expansion versus headers optimization: Reductions
- From: OndÅej BÃlka <neleai at seznam dot cz>
- To: Mikhail Maltsev <maltsevm at gmail dot com>
- Cc: Andi Kleen <andi at firstfloor dot org>, gcc at gcc dot gnu dot org, libc-alpha at sourceware dot org
- Date: Sat, 6 Jun 2015 14:42:43 +0200
- Subject: Re: Builtin expansion versus headers optimization: Reductions
- Authentication-results: sourceware.org; auth=none
- References: <20150604105929 dot GA19141 at domone> <87fv67nonj dot fsf at tassilo dot jf dot intel dot com> <20150605090203 dot GA16032 at domone> <557163E8 dot 3010504 at gmail dot com>
On Fri, Jun 05, 2015 at 12:55:04PM +0400, Mikhail Maltsev wrote:
> 05.06.2015 13:02, OndÅej BÃlka writes:
> > Also as I mentioned bugs before gcc now doesn't handle alignment well so
> > it doesn't optimize following to zero for aligned code.
> >
> > align = ((uintptr_t) x) % 16;
> >
> That is because GCC is conservative and supports some non-ABI-compliant
> memory allocators which only guarantee 8-byte alignment, but
>
Then adding these annotations wouldn't help much as one could interpose
malloc and violate that, unless we rule out that it shouldn't be
replaced by noncompilant one.