* [Bug middle-end/103439] genemit emits dead code
2021-11-26 12:10 [Bug middle-end/103439] New: genemit emits dead code rguenth at gcc dot gnu.org
@ 2021-11-26 12:26 ` ubizjak at gmail dot com
2021-11-26 12:28 ` rguenther at suse dot de
` (4 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: ubizjak at gmail dot com @ 2021-11-26 12:26 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103439
--- Comment #1 from Uroš Bizjak <ubizjak at gmail dot com> ---
(In reply to Richard Biener from comment #0)
> I'm not sure if there are valid cases where we have a mix of a direct
> RTL pattern and manual expansion, so where the { } part falls thru.
Yes, we have quite some of them in e.g. i386.md, movstrict<mode>, extv<mode>,
extzv<mode>, insv<mode> and zero_extend expanders are some of them.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug middle-end/103439] genemit emits dead code
2021-11-26 12:10 [Bug middle-end/103439] New: genemit emits dead code rguenth at gcc dot gnu.org
2021-11-26 12:26 ` [Bug middle-end/103439] " ubizjak at gmail dot com
@ 2021-11-26 12:28 ` rguenther at suse dot de
2021-11-26 13:11 ` ubizjak at gmail dot com
` (3 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: rguenther at suse dot de @ 2021-11-26 12:28 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103439
--- Comment #2 from rguenther at suse dot de <rguenther at suse dot de> ---
On Fri, 26 Nov 2021, ubizjak at gmail dot com wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103439
>
> --- Comment #1 from Uroš Bizjak <ubizjak at gmail dot com> ---
> (In reply to Richard Biener from comment #0)
> > I'm not sure if there are valid cases where we have a mix of a direct
> > RTL pattern and manual expansion, so where the { } part falls thru.
>
> Yes, we have quite some of them in e.g. i386.md, movstrict<mode>, extv<mode>,
> extzv<mode>, insv<mode> and zero_extend expanders are some of them.
OK, so that's conditional FAILs. I've not yet found a conditional
DONE that eventually falls through to a "DONE via the pattern".
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug middle-end/103439] genemit emits dead code
2021-11-26 12:10 [Bug middle-end/103439] New: genemit emits dead code rguenth at gcc dot gnu.org
2021-11-26 12:26 ` [Bug middle-end/103439] " ubizjak at gmail dot com
2021-11-26 12:28 ` rguenther at suse dot de
@ 2021-11-26 13:11 ` ubizjak at gmail dot com
2021-11-26 13:38 ` rguenth at gcc dot gnu.org
` (2 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: ubizjak at gmail dot com @ 2021-11-26 13:11 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103439
--- Comment #3 from Uroš Bizjak <ubizjak at gmail dot com> ---
(In reply to rguenther@suse.de from comment #2)
> On Fri, 26 Nov 2021, ubizjak at gmail dot com wrote:
>
> > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103439
> >
> > --- Comment #1 from Uroš Bizjak <ubizjak at gmail dot com> ---
> > (In reply to Richard Biener from comment #0)
> > > I'm not sure if there are valid cases where we have a mix of a direct
> > > RTL pattern and manual expansion, so where the { } part falls thru.
> >
> > Yes, we have quite some of them in e.g. i386.md, movstrict<mode>, extv<mode>,
> > extzv<mode>, insv<mode> and zero_extend expanders are some of them.
>
> OK, so that's conditional FAILs. I've not yet found a conditional
> DONE that eventually falls through to a "DONE via the pattern".
Look at zero_extend and extend expanders.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug middle-end/103439] genemit emits dead code
2021-11-26 12:10 [Bug middle-end/103439] New: genemit emits dead code rguenth at gcc dot gnu.org
` (2 preceding siblings ...)
2021-11-26 13:11 ` ubizjak at gmail dot com
@ 2021-11-26 13:38 ` rguenth at gcc dot gnu.org
2021-11-26 22:06 ` pinskia at gcc dot gnu.org
2021-11-29 7:21 ` rguenth at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: rguenth at gcc dot gnu.org @ 2021-11-26 13:38 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103439
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Uroš Bizjak from comment #3)
> (In reply to rguenther@suse.de from comment #2)
> > On Fri, 26 Nov 2021, ubizjak at gmail dot com wrote:
> >
> > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103439
> > >
> > > --- Comment #1 from Uroš Bizjak <ubizjak at gmail dot com> ---
> > > (In reply to Richard Biener from comment #0)
> > > > I'm not sure if there are valid cases where we have a mix of a direct
> > > > RTL pattern and manual expansion, so where the { } part falls thru.
> > >
> > > Yes, we have quite some of them in e.g. i386.md, movstrict<mode>, extv<mode>,
> > > extzv<mode>, insv<mode> and zero_extend expanders are some of them.
> >
> > OK, so that's conditional FAILs. I've not yet found a conditional
> > DONE that eventually falls through to a "DONE via the pattern".
>
> Look at zero_extend and extend expanders.
Indeed.
(define_expand "zero_extendqihi2"
[(set (match_operand:HI 0 "register_operand")
(zero_extend:HI (match_operand:QI 1 "nonimmediate_operand")))]
""
{
if (TARGET_ZERO_EXTEND_WITH_AND && optimize_function_for_speed_p (cfun))
{
operands[1] = force_reg (QImode, operands[1]);
emit_insn (gen_zero_extendqihi2_and (operands[0], operands[1]));
DONE;
}
})
and
/* /home/rguenther/src/trunk/gcc/config/i386/i386.md:4120 */
rtx
gen_zero_extendqihi2 (rtx operand0,
rtx operand1)
{
rtx_insn *_val = 0;
start_sequence ();
{
rtx operands[2];
operands[0] = operand0;
operands[1] = operand1;
#define FAIL return (end_sequence (), _val)
#define DONE return (_val = get_insns (), end_sequence (), _val)
#line 4124 "/home/rguenther/src/trunk/gcc/config/i386/i386.md"
{
if (TARGET_ZERO_EXTEND_WITH_AND && optimize_function_for_speed_p (cfun))
{
operands[1] = force_reg (QImode, operands[1]);
emit_insn (gen_zero_extendqihi2_and (operands[0], operands[1]));
DONE;
}
}
#undef DONE
#undef FAIL
operand0 = operands[0];
(void) operand0;
operand1 = operands[1];
(void) operand1;
}
emit_insn (gen_rtx_SET (operand0,
gen_rtx_ZERO_EXTEND (HImode,
operand1)));
_val = get_insns ();
end_sequence ();
return _val;
}
so quite hard if not impossible to "fix" in genemit
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug middle-end/103439] genemit emits dead code
2021-11-26 12:10 [Bug middle-end/103439] New: genemit emits dead code rguenth at gcc dot gnu.org
` (3 preceding siblings ...)
2021-11-26 13:38 ` rguenth at gcc dot gnu.org
@ 2021-11-26 22:06 ` pinskia at gcc dot gnu.org
2021-11-29 7:21 ` rguenth at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-11-26 22:06 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103439
--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #4)
> so quite hard if not impossible to "fix" in genemit
The most complex one I saw in action was mod<mode>3 in aarch64.md:
(define_expand "mod<mode>3"
[(match_operand:GPI 0 "register_operand")
(match_operand:GPI 1 "register_operand")
(match_operand:GPI 2 "const_int_operand")]
Where the pattern in the expand is not going to be used at all (obviously) but
has a conditional FAIL and then an unconditional DONE.
if (val <= 0
|| exact_log2 (val) <= 0
|| !aarch64_bitmask_imm (val - 1, <MODE>mode))
FAIL;
....
rtx masked_neg = gen_reg_rtx (<MODE>mode);
emit_insn (gen_and<mode>3 (masked_neg, neg_op, mask));
emit_insn (gen_csneg3<mode>_insn (operands[0], cond,
masked_neg, masked_pos));
DONE;
And even splits will have issues too. See "*compare_condjump<GPI:mode>" in
aarch64 where the pattern in the split will not be used but then there is an
unconditional DONE:
emit_jump_insn (gen_condjump (cmp_rtx, cc_reg, operands[2]));
DONE;
I think we should just close this as won't fix and add -Wno-unreachable-code
while compiling the generated C file.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug middle-end/103439] genemit emits dead code
2021-11-26 12:10 [Bug middle-end/103439] New: genemit emits dead code rguenth at gcc dot gnu.org
` (4 preceding siblings ...)
2021-11-26 22:06 ` pinskia at gcc dot gnu.org
@ 2021-11-29 7:21 ` rguenth at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: rguenth at gcc dot gnu.org @ 2021-11-29 7:21 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103439
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |WONTFIX
Status|UNCONFIRMED |RESOLVED
--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
OK, agreed.
^ permalink raw reply [flat|nested] 7+ messages in thread