[Bug target/95125] Unoptimal code for vectorized conversions
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95125 --- Comment #11 from Hongtao.liu --- (In reply to Andrew Pinski from comment #10) > float_double and fix_double don't produce the best code yet. It's because loop vectorizer can only use one vector size, since BB vect supports different vector sizes in the same instance, w/ "-O2 -ftree-slp-vectorize -march=skylake-avx512 -funroll-loops" produce optimal codes, this is related to PR101097.
[Bug target/95125] Unoptimal code for vectorized conversions
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95125 --- Comment #10 from Andrew Pinski --- float_double and fix_double don't produce the best code yet.
[Bug target/95125] Unoptimal code for vectorized conversions
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95125 --- Comment #9 from CVS Commits --- The master branch has been updated by hongtao Liu : https://gcc.gnu.org/g:94c0409717bf8bf783963c1d50bb8f4a4732dce7 commit r11-596-g94c0409717bf8bf783963c1d50bb8f4a4732dce7 Author: liuhongt Date: Sat May 23 15:30:58 2020 +0800 Add missing expander for vector float_extend and float_truncate. 2020-05-25 Hongtao Liu gcc/ChangeLog PR target/95125 * config/i386/sse.md (sf2dfmode_lower): New mode attribute. (trunc2) New expander. (extend2): Ditto. gcc/testsuite/ChangeLog * gcc.target/i386/pr95125-avx.c: New test. * gcc.target/i386/pr95125-avx512f.c: Ditto.
[Bug target/95125] Unoptimal code for vectorized conversions
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95125
--- Comment #8 from rsandifo at gcc dot gnu.org
---
(In reply to Richard Biener from comment #7)
> (In reply to Uroš Bizjak from comment #6)
> > (In reply to Hongtao.liu from comment #5)
> > > (In reply to Uroš Bizjak from comment #3)
> > > > It turns out that a bunch of patterns have to be renamed (and testcases
> > > > added).
> > > >
> > > > Easyhack, waiting for someone to show some love to conversion patterns
> > > > in
> > > > sse.md.
> > >
> > > expander for floatv4siv4df2, fix_truncv4dfv4si2 already exists.
> > >
> > > if change **float_double fix_double** to
> > > ---
> > > void
> > > float_double (void)
> > > {
> > > d[0] = i[0];
> > > d[1] = i[1];
> > > d[2] = i[2];
> > > d[3] = i[3];
> > > }
> >
> > Hm, the above is vectorized, but the equivalent:
> >
> > void
> > float_double (void)
> > {
> > for (int n = 0; n < 4; n++)
> > d[n] = i[n];
> > }
> >
> > is not?
>
> Yes, we're committing to a too high VF here, likely because we pick the
> "wrong" vector mode too early. We could eventually fix this up in
> the early vectype analysis.
It might be worth investigating VECT_COMPARE_COSTS, which weighs
the cost of different VFs against each other and is how SVE copes
with this. I guess the danger is that it might interfere with
-mprefer-* options (although the first VF listed by
autovectorize_vector_modes wins in a tie).
[Bug target/95125] Unoptimal code for vectorized conversions
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95125
Richard Biener changed:
What|Removed |Added
CC||rsandifo at gcc dot gnu.org
--- Comment #7 from Richard Biener ---
(In reply to Uroš Bizjak from comment #6)
> (In reply to Hongtao.liu from comment #5)
> > (In reply to Uroš Bizjak from comment #3)
> > > It turns out that a bunch of patterns have to be renamed (and testcases
> > > added).
> > >
> > > Easyhack, waiting for someone to show some love to conversion patterns in
> > > sse.md.
> >
> > expander for floatv4siv4df2, fix_truncv4dfv4si2 already exists.
> >
> > if change **float_double fix_double** to
> > ---
> > void
> > float_double (void)
> > {
> > d[0] = i[0];
> > d[1] = i[1];
> > d[2] = i[2];
> > d[3] = i[3];
> > }
>
> Hm, the above is vectorized, but the equivalent:
>
> void
> float_double (void)
> {
> for (int n = 0; n < 4; n++)
> d[n] = i[n];
> }
>
> is not?
Yes, we're committing to a too high VF here, likely because we pick the
"wrong" vector mode too early. We could eventually fix this up in
the early vectype analysis.
[Bug target/95125] Unoptimal code for vectorized conversions
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95125
Uroš Bizjak changed:
What|Removed |Added
CC||rguenth at gcc dot gnu.org
--- Comment #6 from Uroš Bizjak ---
(In reply to Hongtao.liu from comment #5)
> (In reply to Uroš Bizjak from comment #3)
> > It turns out that a bunch of patterns have to be renamed (and testcases
> > added).
> >
> > Easyhack, waiting for someone to show some love to conversion patterns in
> > sse.md.
>
> expander for floatv4siv4df2, fix_truncv4dfv4si2 already exists.
>
> if change **float_double fix_double** to
> ---
> void
> float_double (void)
> {
> d[0] = i[0];
> d[1] = i[1];
> d[2] = i[2];
> d[3] = i[3];
> }
Hm, the above is vectorized, but the equivalent:
void
float_double (void)
{
for (int n = 0; n < 4; n++)
d[n] = i[n];
}
is not?
[Bug target/95125] Unoptimal code for vectorized conversions
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95125
--- Comment #5 from Hongtao.liu ---
(In reply to Uroš Bizjak from comment #3)
> It turns out that a bunch of patterns have to be renamed (and testcases
> added).
>
> Easyhack, waiting for someone to show some love to conversion patterns in
> sse.md.
expander for floatv4siv4df2, fix_truncv4dfv4si2 already exists.
if change **float_double fix_double** to
---
void
float_double (void)
{
d[0] = i[0];
d[1] = i[1];
d[2] = i[2];
d[3] = i[3];
}
void
fix_double (void)
{
i[0] = d[0];
i[1] = d[1];
i[2] = d[2];
i[3] = d[3];
}
it successfully generate
---
float_double():
vcvtdq2pd i(%rip), %ymm0
vmovapd %ymm0, d(%rip)
vzeroupper
ret
fix_double():
vcvttpd2dqy d(%rip), %xmm0
vmovdqa %xmm0, i(%rip)
ret
l:
-
[Bug target/95125] Unoptimal code for vectorized conversions
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95125 --- Comment #4 from Hongtao.liu --- (In reply to Uroš Bizjak from comment #3) > It turns out that a bunch of patterns have to be renamed (and testcases > added). > > Easyhack, waiting for someone to show some love to conversion patterns in > sse.md. I'll take a look.
[Bug target/95125] Unoptimal code for vectorized conversions
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95125 --- Comment #3 from Uroš Bizjak --- It turns out that a bunch of patterns have to be renamed (and testcases added). Easyhack, waiting for someone to show some love to conversion patterns in sse.md.
[Bug target/95125] Unoptimal code for vectorized conversions
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95125 --- Comment #2 from Uroš Bizjak --- (In reply to Richard Biener from comment #1) > ISTR I filed a duplicate 10 years ago or so. The issue is the vectorizer > could not handle V4DFmode -> V4SFmode conversions. > > Could, because for SVE we added the capability but this requires > additional instruction patterns (IIRC I filed a but about this last > year). Yep. PR92658 it is. Oh... yes. And it is even assigned to me. And there is a patch... ;) Anyway, I got surprised, since my soon-to-be committed v2sf-v2df conversion patch was able to fully vectorize similar testcase involving double[2] and float[2], while code involving [4] compiled to he mess below.
[Bug target/95125] Unoptimal code for vectorized conversions
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95125 Richard Biener changed: What|Removed |Added Version|unknown |11.0 Ever confirmed|0 |1 Last reconfirmed||2020-05-14 Target||x86_64-*-* i?86-*-* Keywords||missed-optimization Status|UNCONFIRMED |NEW --- Comment #1 from Richard Biener --- ISTR I filed a duplicate 10 years ago or so. The issue is the vectorizer could not handle V4DFmode -> V4SFmode conversions. Could, because for SVE we added the capability but this requires additional instruction patterns (IIRC I filed a but about this last year). Yep. PR92658 it is.
