Hi guys,
On Fri, Nov 25, 2022 at 04:11:49PM +0800, Kewen.Lin wrote:
> on 2022/10/26 19:40, Jiufu Guo wrote:
> for "li/lis + oris/xoris", I interpreted it into four combinations:
>
> li + oris, lis + oris, li + xoris, lis + xoris.
>
> not sure just me interpreting like that, but the actual combinations
> which this patch adopts are:
>
> li + oris, li + xoris, lis + xoris.
>
> It's a bit off, but not a big deal, up to you to reword it or not. :)
The first two are obvious, but the last one is almost never a good idea,
there usually are better ways to do the same. I cannot even think of
any case where this is best? A lis;rl* is always prefered (it can
optimise better, be combined with other insns).
> > + HOST_WIDE_INT orig_c = c;
If you ever feel you need a variable to hold an "orig" value, that is a
good hint that you should restructure the code a bit, perhaps even
factor it. That often is overdue (like here), not caused by you, but
you could help solve it ;-)
(This is what made this patch hard to review, btw).
> > gen_rtx_IOR (DImode, copy_rtx (temp),
> > GEN_INT (ud1)));
> > }
> > + else if ((ud4 == 0xffff && ud3 == 0xffff)
> > + && ((ud1 & 0x8000) || (ud1 == 0 && !(ud2 & 0x8000))))
> > + {
> > + temp = !can_create_pseudo_p () ? dest : gen_reg_rtx (DImode);
> > +
> > + HOST_WIDE_INT imm = (ud1 & 0x8000) ? ((ud1 ^ 0x8000) - 0x8000)
> > + : ((ud2 << 16) - 0x80000000);
We really should have some "hwi::sign_extend (ud1, 16)" helper function,
heh. Maybe there already is? Ah, "sext_hwi". Fixing that up
everywhere in this function is preapproved.
> > + else
> > + {
> > + emit_move_insn (temp,
> > + GEN_INT (((ud2 << 16) ^ 0x80000000) - 0x80000000));
> > + if (ud1 != 0)
> > + emit_move_insn (temp, gen_rtx_IOR (DImode, temp, GEN_INT (ud1)));
> > + emit_move_insn (dest,
> > + gen_rtx_ZERO_EXTEND (DImode,
> > + gen_lowpart (SImode, temp)));
> > + }
Why this? Please just write it in DImode, do not go via SImode?
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/powerpc/pr106708.h
> > @@ -0,0 +1,9 @@
> > +/* Test constants which can be built by li/lis + oris/xoris */
> > +void __attribute__ ((__noinline__, __noclone__)) foo (long long *arg)
> > +{
> > + *arg++ = 0x98765432ULL;
> > + *arg++ = 0xffffffff7cdeab55ULL;
> > + *arg++ = 0xffffffff65430000ULL;
> > +}
Use noipa please (it is shorter, simpler, and covers more :-) )
Could you comment what exact instructions are expected?
li;xoris and li;xoris and lis;xoris I guess? It helps if you just tell
the reader here.
The li;oris and li;xoris parts look good.
Segher
