[Date Prev][Date Next] [Thread Prev][Thread Next] [Date Index] [Thread Index]

Re: Help on memchr() EGLIBC assembly code

On Mon, Jul 13, 2009 at 02:24:00PM -0400, Carlos O'Donell wrote:
> On Mon, Jul 13, 2009 at 1:31 PM, Aurelien Jarno<aurelien@aurel32.net> wrote:
> > With a lot of patches (E)GLIBC 2.10 builds on alpha, but it fails on the
> > testsuite for the memchr() function, which is an optimized assembly code
> > on alpha. Unfortunately I don't speak alpha assembly very well, so help
> > is needed.
> >
> > The problem is that the memchr() function on alpha uses prefetch, which
> > can cause a page boundary to be crossed, while the standards (POSIX and
> > C99) says it should stop when a match is found.
> >
> > I have built a small testcase (see file attached), which contains the
> > code to trigger the bug and the assembly code of the memchr() function,
> > copied from EGLIBC.
> >
> > It would be nice if someone can fix the assembly code so that the
> > prefetching does not create memory faults. Thanks in advance.
> If you remove:
> ./sysdeps/alpha/alphaev6/memchr.S
> ./sysdeps/alpha/memchr.S
> and allow the build to fallback on string/memchr.c do the tests pass?
> You can always add memchr.S routines back in a later release if you
> need an immediate workaround.

Yeah, it works, and that's actually my plan if I get no answer. But I
would really like to see this fixed now, as otherwise, it will most
probably stay like that indefinitely.

Aurelien Jarno	                        GPG: 1024D/F1BCDB73
aurelien@aurel32.net                 http://www.aurel32.net

Reply to: