On Mon, Nov 22, 2021 at 10:36:13AM -0600, Bill Schmidt wrote:
> Hi Mike,
>
> Thanks for this patch!
> > --- a/gcc/config/rs6000/rs6000.md
> > +++ b/gcc/config/rs6000/rs6000.md
> > @@ -12988,15 +12988,34 @@ (define_expand "indirect_jump"
> > emit_jump_insn (gen_indirect_jump_nospec (Pmode, operands[0], ccreg));
> > DONE;
> > }
> > + if (TARGET_P10_FUSION && TARGET_P10_FUSION_ZERO_CYCLE)
> > + {
> > + emit_jump_insn (gen_indirect_jump_zero_cycle (Pmode, operands[0]));
> > + DONE;
> > + }
> > })
> >
> > (define_insn "*indirect_jump<mode>"
> > [(set (pc)
> > (match_operand:P 0 "register_operand" "c,*l"))]
> > - "rs6000_speculate_indirect_jumps"
> > + "rs6000_speculate_indirect_jumps
> > + && !(TARGET_P10_FUSION && TARGET_P10_FUSION_ZERO_CYCLE)"
> > "b%T0"
> > [(set_attr "type" "jmpreg")])
> >
> > +(define_insn "@indirect_jump<mode>_zero_cycle"
>
> I don't know why this is an "@" pattern, but honestly I don't
> know why @indirect_jump<mode>_nospec is an "@" pattern either.
> The documentation for such things is hard for me to understand,
> so I'm probably just missing something obvious, but I don't
> immediately see why we would need the @ here.
I didn't know about it either. Basically the next insn used it:
(define_insn "@indirect_jump<mode>_nospec"
[(set (pc) (match_operand:P 0 "register_operand" "c,*l"))
(clobber (match_operand:CC 1 "cc_reg_operand" "=y,y"))]
"!rs6000_speculate_indirect_jumps"
"crset %E1\;beq%T0- %1\;b $"
[(set_attr "type" "jmpreg")
(set_attr "length" "12")])
This creates a function:
gen_indirect_jump_nospec (machine_mode arg0, rtx x0, rtx x1)
where the mode of the P iterator is passed as argument. I.e. you can do:
rtx foo = gen_indirect_jump_nospec (Pmode, op0, op1);
instead of:
rtx foo;
if (Pmode == SImode)
foo = gen_indirect_jumpsi_nospec (op0, op1);
else if (Pmode == DImode)
foo = gen_indirect_jumpdi_nospec (op0, op1);
else
gcc_unreachable ();
> > + [(set (pc)
> > + (match_operand:P 0 "register_operand" "r,r,!cl"))
> > + (clobber (match_scratch:P 1 "=c,*l,X"))]
>
> Do we need the *l and X alternatives if we're only doing this for
> mtctr/bctr?
Probably not, but I recall back before the current allocator, that it would
cause crashes if we didn't have LR. I could certainly eliminate the *l
alternative.
--
Michael Meissner, IBM
PO Box 98, Ayer, Massachusetts, USA, 01432
email: meiss...@linux.ibm.com
