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Re: discuss: How to print XMM registers on i386/x86-64
- From: Elena Zannoni <ezannoni at redhat dot com>
- To: Andrew Cagney <ac131313 at cygnus dot com>
- Cc: Andreas Jaeger <aj at suse dot de>, Michal Ludvig <mludvig at suse dot cz>, gdb <gdb at sources dot redhat dot com>
- Date: Thu, 4 Apr 2002 12:56:59 -0500
- Subject: Re: discuss: How to print XMM registers on i386/x86-64
- References: <3CAC6E35.8050302@suse.cz><u8sn6btrjc.fsf@gromit.moeb><3CAC8B94.7020904@cygnus.com>
Andrew Cagney writes:
> > Michal Ludvig <mludvig@suse.cz> writes:
> >
> >
> >> Hi all,
> >> current gdb has a problem with printing xmm registers on i386/x86-64
> >> architectures. XMM regsters are of type builtin_type_v4sf. In 5.1.1
> >> the output of 'comand info registers xmm0' was as follows:
> >>
> >> xmm0 0x00102030405060708090a0b0c0d0e0f0
> >> Now in current mainline it's completely broken (with the same type):
> >>
> >> xmm0 {f = {0x0, 0x0, 0x0, 0x0}} \
> >> {f = {5.82303983e-10, 2.77686634e+29, -1.16826016e-09, \
> >> -5.56616044e+29}}
>
> When you say broken, you mean the output or the values?
>
> >> If I change the type to builtin_type_v4si I get a more useful output:
> >>
> >> xmm0 {f = {0x30201000, 0x70605040, 0xb0a09080, 0xf0e0d0c0}} \
> >> {f = {807407616, 1885360192, -1331654528, -253701952}}
> >>
> >> So my question is how to print it? We shouldn't treat XMM registers as
> >> 4xFP, because it can contain 1) two double precision floats, 2) four
> >> single precision floats, 3) from 16 bytes, 8 words, 4 double words, 2
> >> quadwords or 1 double quadword (128b).
>
>
> The idea behind the registers having struct/union types was to make it
> possible for the user to ``explore'' (and access) sub fields and the
> composite vis:
>
> $xmm0.v4si[1]
> $xmm0.v2di[0]
>
> (don't quote me on the syntax). It sounds like the current type isn't
> sufficient - a union of types is needed?
>
> Can I suggest treating how ``info registers'' displays registers as a
> separate problem - the code is free to display the registers in what
> ever format it sees fit.
>
> >> For now gcc won't store more than one FP variable into each register,
> >> ie. we don't need to convert all parts to float.
>
> I think the full register contents should be displayed - we can't assume
> that the user is using GCC.
>
> Ok, one MMX patch comming right up ...
>
> Andrew
>
>
Another example to look at is the printing of the AltiVec registers.
The code for this is in rs6000-tdep.c.
Elena