Re: discuss: How to print XMM registers on i386/x86-64

[Andrew Cagney <ac131313 at cygnus dot com>]

> 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