Re: Bug#164766: Problem with VIA C3 chip and libcrypto

[Daniel Jacobowitz <dan@debian.org>]

On Fri, Jan 17, 2003 at 09:39:44AM +0900, GOTO Masanori wrote:
> At 16 Jan 2003 18:38:07 +0000,
> Philip Blundell wrote:
> > So, per our IRC discussion this afternoon, I think the current plan for
> > this is to have ld.so treat CMOV as an optional extension, similar to
> > how MMX is handled.  In other words:
> > 
> >  - Add CMOV to HWCAP_IMPORTANT in glibc.
> > 
> >  - Ask the maintainers of openssl and any other affected packages to put
> > their cmov-using libraries in /lib/i686/cmov. 
> > 
> >  - If openssl wants to ship a specific C3-compatible build that only
> > uses mandatory i686 features, it can go in /lib/i686.
> 
> Thanks Philip for summarizing.
> We debian-glibc team plan to prepare cmov-aware libc6.
> 
> 
> To make sure for other people, I add some more words.
> 
> This libc ld.so special handling for hardware capability is used by
> only MMX currently.  We expand it not only for MMX but also CMOV.
> MMX, intel's multi media extension, is also same circumstance that
> both Pentium (i586) and Pentium MMX (i586 MMX) are 'i586 class
> processors'.

This bit is a good idea but...

> Well, his stance is not wrong.
> 
> We can hack gcc not to generate CMOV code with (for example) -mcpu=c3,
> or -mno-cmov (like -mno-mmx), but stil this hardware capability
> handling is needed for dynamic libraries.
> 
> In addition, We don't provide any cmov checking for 'binaries which
> are hand-assembled or gcc generated'.  Hand-assembled binaries should
> check cmov flag like mmx.  If you get 'illegal instruction' with such
> binaries, you submit BTS for such packages.  It's another issue that a
> binary is optmized as i686 with cmov instruction by gcc.  You need to
> consider how to fix.  I anticipate that it may need to make gcc
> non-cmov aware.

Let's not do anything about this until someone gets clarification from
GCC that -march=i686 is not actually supposed to be a 686, OK?

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer