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Re: Simulation of MIPS recip and rsqrt instructions
- From: Richard Sandiford <rsandifo at redhat dot com>
- To: cgd at broadcom dot com
- Cc: gdb-patches at sources dot redhat dot com
- Date: 27 Nov 2002 08:11:59 +0000
- Subject: Re: Simulation of MIPS recip and rsqrt instructions
- References: <m3smxom7q9.fsf@localhost.localdomain><mailpost.1038339722.6479@news-sj1-1> <yov5smxo2hc1.fsf@broadcom.com>
cgd@broadcom.com writes:
> In adding those calls to sim_fpu_inv() I did not notice the changes to
> sim_fpu_inv() in our source which replace its entire body with:
>
> #if 0
> ... old body ...
> #else
> const sim_fpu sim_fpu_one = {
> sim_fpu_class_number, 0, IMPLICIT_1, 0
> };
> return sim_fpu_div (f, &sim_fpu_one, r, sim_fpu_round_default);
> #endif
>
> 8-)
Ah. ;) Out of interest, how come you're using these local constants?
I noticed the same thing in cp1.c. Is it just supposed to lead to
better optimisation than the global sim_fpu_one?
> > Unfortunately, sim_fpu_inv isn't commented and cp1.c seems to be
> > its only active user. Which should change?
>
> For small values of only. 8-)
>
> common/cgen-accfp.c seems to use it as well for "invsf" and "invdf".
Yeah, but nothing seems to use invsf and invdf. AFAICT, the mips
port really is the only active user.
> Anybody got a clue as to what the cgen-accfp.c 'invsf' and 'invdf' fns
> are supposed to do?
Not me. I looked at the cgen docs, but it didn't mention it
explicitly. But like you & Andrew say, it's probably better
to patch sim_fpu_inv(). Please install my second patch if it's
OK. I realise I missed the change log first time, so here it
is again.
Richard
* sim-fpu.c (sim_fpu_inv): Use sim_fpu_div.
Index: sim/common/sim-fpu.c
===================================================================
RCS file: /cvs/src/src/sim/common/sim-fpu.c,v
retrieving revision 1.4
diff -c -d -p -F^[(a-zA-Z0-9_^#] -r1.4 sim-fpu.c
*** sim/common/sim-fpu.c 12 Jun 2002 00:46:11 -0000 1.4
--- sim/common/sim-fpu.c 26 Nov 2002 20:33:46 -0000
*************** INLINE_SIM_FPU (int)
*** 1754,1786 ****
sim_fpu_inv (sim_fpu *f,
const sim_fpu *r)
{
! if (sim_fpu_is_snan (r))
! {
! *f = *r;
! f->class = sim_fpu_class_qnan;
! return sim_fpu_status_invalid_snan;
! }
! if (sim_fpu_is_qnan (r))
! {
! *f = *r;
! f->class = sim_fpu_class_qnan;
! return 0;
! }
! if (sim_fpu_is_infinity (r))
! {
! *f = sim_fpu_zero;
! f->sign = r->sign;
! return 0;
! }
! if (sim_fpu_is_zero (r))
! {
! f->class = sim_fpu_class_infinity;
! f->sign = r->sign;
! return sim_fpu_status_invalid_div0;
! }
! *f = *r;
! f->normal_exp = - r->normal_exp;
! return 0;
}
--- 1754,1760 ----
sim_fpu_inv (sim_fpu *f,
const sim_fpu *r)
{
! return sim_fpu_div (f, &sim_fpu_one, r);
}