Re: New optimized string routines for Intel and alignment of stack.

[Florian Weimer <fweimer at redhat dot com>]

On 06/11/2016 08:01 AM, Mike Frysinger wrote:
> On 07 Jun 2016 17:35, Joseph Myers wrote:
> > On Tue, 7 Jun 2016, Florian Weimer wrote:
> > > On 06/07/2016 07:56 AM, Carlos O'Donell wrote:
> > > > We have had several users that have built legacy applications
> > > > for 32-bit x86 with stack alignment that does not match the
> > > > ABI.
> > >
> > > Let's say the GNU project broke the i386 ABI, which is more accurate. The
> > > stack pointer alignment requirement is a recent change.
> >
> > I place the ABI change around 2006, when GCC stopped using
> > -mpreferred-stack-boundary=2 even with -Os, and so compatibility
> > requirements as applying to GLIBC_2.4 and older symbols.
> >
> > https://sourceware.org/ml/libc-alpha/2013-08/msg00372.html
>
> indeed, the ship has sailed.  i don't think trying to revert things after
> 10 years makes sense.
>
> https://groups.google.com/forum/#!msg/ia32-abi/T5s-UGmUO_E/0-9QgPuB8_MJ

Yeah, I didn't realize the only thing that might work is âpreserve 
alignment, but don't rely on itâ.  Performance-wise, this is the worst 
option.  But maybe we should do this in glibc.

Florian