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Re: [RFA] gdbtypes.[ch] rs6000-tdep.c--AltiVec regs types


Daniel Jacobowitz wrote:
> 
> On Fri, Jan 11, 2002 at 05:32:45PM -0500, Elena Zannoni wrote:
> >
> > This patch provides a builtin union type for the AltiVec registers,
> > so that the printing of such regs is a bit more enlightening, like:
> >
> >
> > (gdb) p $vr0
> > $2 = {uint128 = 0x00000064000000c80000012c00000190,
> >       v4sf = {f = {1.40129846e-43, 2.80259693e-43, 4.20389539e-43, 5.60519386e-43}},
> >       v4si = {f = {100, 200, 300, 400}},
> >       v8hi = {f = {0, 100, 0, 200, 0, 300, 0, 400}},
> >       v16qi = {f = "\0\0\0d\0\0\0\0\0\001,\0\0\001\220"}}
> > (gdb) p $vr0.v4si
> > $3 = {f = {100, 200, 300, 400}}
> > (gdb) p $vr0.v4si.f[2]
> > $4 = 300
> > (gdb) p $vr0.v4si.f[2]=444
> > $5 = 444
> 
> Why is the .f necessary?  Why not make $vr0.v4si an array rather than
> struct type?

I know this is historical (it's been done the same way for other
targets), 
and I'm guessing it's because a struct type can be passed by value,
while
an array type is always passed by reference.  You want a type that can
be passed to a function.

I should know this (I've dealt with it before), but my 
memory cache is shrinking with age and misuse.  ;-(


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