Re: RFC: partially available registers

Pedro Alves
2011-07-27T19:26:43Z

On Wednesday 27 July 2011 20:08:26, Tom Tromey wrote:
> Pedro> ... but I think that we should go with 0, instead of <unavailable>,
> Pedro> meaning changing x87-tdep.c:i387_supply_xsave to supply
> Pedro> explicity zeroed buffer, instead of a NULL pointer, like
> Pedro> gdbserver does.
>
> Tom> I will do this.
>
> Here's the patch.

Thanks. Why only the AVX state though? There are
several other places in the same function that
pass NULL to regcache_raw_supply that I think
should get the same treatment.

i387_supply_xsave accepts and handles a NULL XSAVE
argument. I suppose it's for cores that miss the
xsave section? I can't quite tell what path ends
up calling i387_supply_xsave with NULL. Maybe it's
dead code (I remember this code having changed a bit
the design throughout the review iterations; this bit may
have been left behind). If not dead, that may be a genuine
case for <unavailable>.

>
> In absence of comment I will check it in, in a couple of days.
>
> Built and regtested by the buildbot.
>
> Tom
>
> 2011-07-27 Tom Tromey <tromey@redhat.com>
>
> * i387-tdep.c (i387_supply_xsave): Supply zero for high bits of
> AVX registers.
>
> diff --git a/gdb/i387-tdep.c b/gdb/i387-tdep.c
> index c4ace82..332d491 100644
> --- a/gdb/i387-tdep.c
> +++ b/gdb/i387-tdep.c
> @@ -798,17 +798,26 @@ i387_supply_xsave (struct regcache *regcache, int regnum,
> /* Handle the upper YMM registers. */
> if ((tdep->xcr0 & I386_XSTATE_AVX))
> {
> + gdb_byte buf[MAX_REGISTER_SIZE];
> +
> if ((clear_bv & I386_XSTATE_AVX))
> - p = NULL;
> + {
> + memset (buf, 0, sizeof (buf));
> + p = NULL;
> + }
> else
> p = regs;
>
> for (i = I387_YMM0H_REGNUM (tdep);
> i < I387_YMMENDH_REGNUM (tdep); i++)
> {
> + const void *arg;
> +
> if (p != NULL)
> - p = XSAVE_AVXH_ADDR (tdep, regs, i);
> - regcache_raw_supply (regcache, i, p);
> + arg = XSAVE_AVXH_ADDR (tdep, regs, i);
> + else
> + arg = buf;
> + regcache_raw_supply (regcache, i, arg);
> }
> }
>
>

--
Pedro Alves