> > *Maybe* the register functions need to be a little smarter, by
> > first choosing any register whose regno field matches the ideal
> > number, then choosing the best register out of that set that fits
> > the other criteria best.
> >
> > (This is all crash-course hacking I'm doing, so I might be
> > totally mistaken).
>
> The "rreg_ideal" functions did more-or-less that, if I recall (it's been
> about a year since I did the same crash course your're doing now).
Hmm, I think I ran into a similar problem rreg_ideal_int()... Here is an
excerpt from the "pusharg_int" section of the PowerPC backend:
if( (w = next_arg_register(a, Rint, &r_count)) != -1 )
{
#if 0
/*
* We can pass the arg in a register. Ask for the register
* we were given (rreg_int(1)) to be mapped to the one we
* want (w).
*/
r = rreg_ideal_int(1, w);
if( r != w )
{
/* They weren't the same, flush whatever is in "w" */
clobberRegister(w);
/* and move the data into it. */
LOUT = ppc_op_mr(w, r);
/* XXX Why isn't there a register swap? */
}
/* Pin the register. */
register_reserve(w);
#else
/*
* can't use rreg_ideal_int because of brokeness. its possible
* for this to create a move between a callee saved register
* and a caller saved regsiter. And, since the pushargs are
* run after the function_sync that does the spill, we can lose
* the data in the register.
*/
r = rreg_int(1);
if( r != w )
{
clobberRegister(w);
LOUT = ppc_op_mr(w, r);
}
register_reserve(w);
#endif
And, here is the analogous section of the mips jitter:
if (arg_idx < NR_ARGUMENTS) {
o = REG_i4 + arg_idx;
r = rreg_ideal_int(1, o);
/* We might not get the ideal register (if the slot is global)
* so handle this.
*/
if (r != o) {
clobberRegister(o);
insn_RRR(_ADDU, o, r, REG_i0);
debug((" mov %s,%s\n", regname(o), regname(r)));
r = o;
}
register_reserve(r);
resreg[res_idx++] = r;
Perhaps you should try without the rreg_ideal_int()?
> Regards,
>
> Kevin K.
tim
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