* [PATCH] tree-optimization/113552 - fix num_call accounting in simd clone vectorization @ 2024-01-23 11:56 Richard Biener 2024-01-23 12:01 ` Jakub Jelinek 0 siblings, 1 reply; 6+ messages in thread From: Richard Biener @ 2024-01-23 11:56 UTC (permalink / raw) To: gcc-patches The following avoids using exact_log2 on the number of SIMD clone calls to be emitted when vectorizing calls since that can easily be not a power of two in which case it will return -1. For different simd clones the number of calls will differ by a multiply with a power of two only so using floor_log2 is good enough here. Bootstrap and regtest running on x86_64-unknown-linux-gnu. PR tree-optimization/113552 * tree-vect-stmts.cc (vectorizable_simd_clone_call): Use floor_log2 instead of exact_log2 on the number of calls. --- gcc/tree-vect-stmts.cc | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc index 09749ae3817..1dbe1115da4 100644 --- a/gcc/tree-vect-stmts.cc +++ b/gcc/tree-vect-stmts.cc @@ -4071,7 +4071,7 @@ vectorizable_simd_clone_call (vec_info *vinfo, stmt_vec_info stmt_info, || (nargs != simd_nargs)) continue; if (num_calls != 1) - this_badness += exact_log2 (num_calls) * 4096; + this_badness += floor_log2 (num_calls) * 4096; if (n->simdclone->inbranch) this_badness += 8192; int target_badness = targetm.simd_clone.usable (n); -- 2.35.3 ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] tree-optimization/113552 - fix num_call accounting in simd clone vectorization 2024-01-23 11:56 [PATCH] tree-optimization/113552 - fix num_call accounting in simd clone vectorization Richard Biener @ 2024-01-23 12:01 ` Jakub Jelinek 2024-01-23 12:03 ` Richard Biener 0 siblings, 1 reply; 6+ messages in thread From: Jakub Jelinek @ 2024-01-23 12:01 UTC (permalink / raw) To: Richard Biener; +Cc: gcc-patches On Tue, Jan 23, 2024 at 12:56:52PM +0100, Richard Biener wrote: > The following avoids using exact_log2 on the number of SIMD clone calls > to be emitted when vectorizing calls since that can easily be not > a power of two in which case it will return -1. For different simd > clones the number of calls will differ by a multiply with a power of two > only so using floor_log2 is good enough here. > > Bootstrap and regtest running on x86_64-unknown-linux-gnu. > > PR tree-optimization/113552 > * tree-vect-stmts.cc (vectorizable_simd_clone_call): Use > floor_log2 instead of exact_log2 on the number of calls. Is there any target which supports non-power-of-two simdlen? If not, perhaps we should add !pow2p_hwi (num_calls) to the continue; condition a few lines earlier? > diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc > index 09749ae3817..1dbe1115da4 100644 > --- a/gcc/tree-vect-stmts.cc > +++ b/gcc/tree-vect-stmts.cc > @@ -4071,7 +4071,7 @@ vectorizable_simd_clone_call (vec_info *vinfo, stmt_vec_info stmt_info, > || (nargs != simd_nargs)) > continue; > if (num_calls != 1) > - this_badness += exact_log2 (num_calls) * 4096; > + this_badness += floor_log2 (num_calls) * 4096; > if (n->simdclone->inbranch) > this_badness += 8192; > int target_badness = targetm.simd_clone.usable (n); > -- > 2.35.3 Jakub ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] tree-optimization/113552 - fix num_call accounting in simd clone vectorization 2024-01-23 12:01 ` Jakub Jelinek @ 2024-01-23 12:03 ` Richard Biener 2024-01-23 12:21 ` Jakub Jelinek 0 siblings, 1 reply; 6+ messages in thread From: Richard Biener @ 2024-01-23 12:03 UTC (permalink / raw) To: Jakub Jelinek; +Cc: gcc-patches On Tue, 23 Jan 2024, Jakub Jelinek wrote: > On Tue, Jan 23, 2024 at 12:56:52PM +0100, Richard Biener wrote: > > The following avoids using exact_log2 on the number of SIMD clone calls > > to be emitted when vectorizing calls since that can easily be not > > a power of two in which case it will return -1. For different simd > > clones the number of calls will differ by a multiply with a power of two > > only so using floor_log2 is good enough here. > > > > Bootstrap and regtest running on x86_64-unknown-linux-gnu. > > > > PR tree-optimization/113552 > > * tree-vect-stmts.cc (vectorizable_simd_clone_call): Use > > floor_log2 instead of exact_log2 on the number of calls. > > Is there any target which supports non-power-of-two simdlen? > If not, perhaps we should add !pow2p_hwi (num_calls) to the continue; > condition a few lines earlier? Is non-power-of-two simdlen a thing? Note there's nothing wrong with non-power-of-two num_calls, with VF == 4 and a group size of 3 you get 12 lanes and either 3 (simdlen == 4) or 6 (simdlen == 2) calls. Iff non-power-of-two simdlen is a thing then we could bias by + num_calls (no idea why we use *_log2 in the first place, but it was that way since the beginning). Richard. > > diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc > > index 09749ae3817..1dbe1115da4 100644 > > --- a/gcc/tree-vect-stmts.cc > > +++ b/gcc/tree-vect-stmts.cc > > @@ -4071,7 +4071,7 @@ vectorizable_simd_clone_call (vec_info *vinfo, stmt_vec_info stmt_info, > > || (nargs != simd_nargs)) > > continue; > > if (num_calls != 1) > > - this_badness += exact_log2 (num_calls) * 4096; > > + this_badness += floor_log2 (num_calls) * 4096; > > if (n->simdclone->inbranch) > > this_badness += 8192; > > int target_badness = targetm.simd_clone.usable (n); > > -- > > 2.35.3 > > Jakub > > -- Richard Biener <rguenther@suse.de> SUSE Software Solutions Germany GmbH, Frankenstrasse 146, 90461 Nuernberg, Germany; GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg) ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] tree-optimization/113552 - fix num_call accounting in simd clone vectorization 2024-01-23 12:03 ` Richard Biener @ 2024-01-23 12:21 ` Jakub Jelinek 2024-01-23 12:40 ` Richard Biener 0 siblings, 1 reply; 6+ messages in thread From: Jakub Jelinek @ 2024-01-23 12:21 UTC (permalink / raw) To: Richard Biener; +Cc: gcc-patches On Tue, Jan 23, 2024 at 01:03:46PM +0100, Richard Biener wrote: > On Tue, 23 Jan 2024, Jakub Jelinek wrote: > > > On Tue, Jan 23, 2024 at 12:56:52PM +0100, Richard Biener wrote: > > > The following avoids using exact_log2 on the number of SIMD clone calls > > > to be emitted when vectorizing calls since that can easily be not > > > a power of two in which case it will return -1. For different simd > > > clones the number of calls will differ by a multiply with a power of two > > > only so using floor_log2 is good enough here. > > > > > > Bootstrap and regtest running on x86_64-unknown-linux-gnu. > > > > > > PR tree-optimization/113552 > > > * tree-vect-stmts.cc (vectorizable_simd_clone_call): Use > > > floor_log2 instead of exact_log2 on the number of calls. > > > > Is there any target which supports non-power-of-two simdlen? > > If not, perhaps we should add !pow2p_hwi (num_calls) to the continue; > > condition a few lines earlier? > > Is non-power-of-two simdlen a thing? Note there's nothing wrong > with non-power-of-two num_calls, with VF == 4 and a group size > of 3 you get 12 lanes and either 3 (simdlen == 4) or 6 (simdlen == 2) > calls. > > Iff non-power-of-two simdlen is a thing then we could bias > by + num_calls (no idea why we use *_log2 in the first place, but it > was that way since the beginning). Ah, with SLP I can understand it doesn't have to be a power of two, the original + if (n->simdclone->simdlen + < (unsigned) LOOP_VINFO_VECT_FACTOR (loop_vinfo)) + this_badness += (exact_log2 (LOOP_VINFO_VECT_FACTOR (loop_vinfo)) + - exact_log2 (n->simdclone->simdlen)) * 1024; was written for loop vectorization only and I think correctly assumed power of 2 loop vectorization factors as well as simdlens. I admit I don't remember why log2 rather than the count has been used, the first version of the patch is https://gcc.gnu.org/pipermail/gcc-patches/2013-November/374728.html But if we keep using log2, perhaps better ceil_log2 because num_calls of 3 is certainly more expensive than 2. Jakub ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] tree-optimization/113552 - fix num_call accounting in simd clone vectorization 2024-01-23 12:21 ` Jakub Jelinek @ 2024-01-23 12:40 ` Richard Biener 2024-01-23 12:43 ` Jakub Jelinek 0 siblings, 1 reply; 6+ messages in thread From: Richard Biener @ 2024-01-23 12:40 UTC (permalink / raw) To: Jakub Jelinek; +Cc: gcc-patches On Tue, 23 Jan 2024, Jakub Jelinek wrote: > On Tue, Jan 23, 2024 at 01:03:46PM +0100, Richard Biener wrote: > > On Tue, 23 Jan 2024, Jakub Jelinek wrote: > > > > > On Tue, Jan 23, 2024 at 12:56:52PM +0100, Richard Biener wrote: > > > > The following avoids using exact_log2 on the number of SIMD clone calls > > > > to be emitted when vectorizing calls since that can easily be not > > > > a power of two in which case it will return -1. For different simd > > > > clones the number of calls will differ by a multiply with a power of two > > > > only so using floor_log2 is good enough here. > > > > > > > > Bootstrap and regtest running on x86_64-unknown-linux-gnu. > > > > > > > > PR tree-optimization/113552 > > > > * tree-vect-stmts.cc (vectorizable_simd_clone_call): Use > > > > floor_log2 instead of exact_log2 on the number of calls. > > > > > > Is there any target which supports non-power-of-two simdlen? > > > If not, perhaps we should add !pow2p_hwi (num_calls) to the continue; > > > condition a few lines earlier? > > > > Is non-power-of-two simdlen a thing? Note there's nothing wrong > > with non-power-of-two num_calls, with VF == 4 and a group size > > of 3 you get 12 lanes and either 3 (simdlen == 4) or 6 (simdlen == 2) > > calls. > > > > Iff non-power-of-two simdlen is a thing then we could bias > > by + num_calls (no idea why we use *_log2 in the first place, but it > > was that way since the beginning). > > Ah, with SLP I can understand it doesn't have to be a power of two, > the original > + if (n->simdclone->simdlen > + < (unsigned) LOOP_VINFO_VECT_FACTOR (loop_vinfo)) > + this_badness += (exact_log2 (LOOP_VINFO_VECT_FACTOR (loop_vinfo)) > + - exact_log2 (n->simdclone->simdlen)) * 1024; > was written for loop vectorization only and I think correctly assumed > power of 2 loop vectorization factors as well as simdlens. Note even without SLP we could vectorize a group size of 3 with interleaving. But yes, VF for interleaving is a power of two and so is simdlen so the above should have worked. > I admit I don't remember why log2 rather than the count has been used, > the first version of the patch is > https://gcc.gnu.org/pipermail/gcc-patches/2013-November/374728.html > But if we keep using log2, perhaps better ceil_log2 because num_calls of > 3 is certainly more expensive than 2. I think only the relative accounting to the other this_badness increments matter since as said, at least with power-of-two simdlen we'd get different {ceil,floor}_log2 values for different simdlen. It's never going to be 3 vs 2 but 3 * 2^n vs. 3 * 2^m so floor or ceil doesn't matter. In fact we could have just using some inverse of exact_log2 (n->simdclone->simdlen). That is, it's only simdlen that's varying in this addend to this_badness. For the exact_log2 case the behavior is unchanged and we now only get a sensible number for the others now. Maybe log2 was for the fear of overflow or over-accounting compared to the other increments. When overflow is not an issue we could also use floor_log2 (num_calls * 4096) to be more "precise". I don't know why we have all these different weights and why they are the way they are - but it's a lot of apples and oranges we put together in a magic number to compare ;) I prefer to do a minimal change now, but both floor and ceil work for me, so if you prefer I can change (but as said, it would only matter with the mixing with the other cost factors, and in unknown ways since the desire is not spelled out). Richard. ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] tree-optimization/113552 - fix num_call accounting in simd clone vectorization 2024-01-23 12:40 ` Richard Biener @ 2024-01-23 12:43 ` Jakub Jelinek 0 siblings, 0 replies; 6+ messages in thread From: Jakub Jelinek @ 2024-01-23 12:43 UTC (permalink / raw) To: Richard Biener; +Cc: gcc-patches On Tue, Jan 23, 2024 at 01:40:15PM +0100, Richard Biener wrote: > It's never going to be 3 vs 2 but 3 * 2^n vs. 3 * 2^m so floor or > ceil doesn't matter. In fact we could have just using > some inverse of exact_log2 (n->simdclone->simdlen). That is, > it's only simdlen that's varying in this addend to this_badness. > > For the exact_log2 case the behavior is unchanged and we now only > get a sensible number for the others now. Maybe log2 was for the > fear of overflow or over-accounting compared to the other increments. > When overflow is not an issue we could also use > floor_log2 (num_calls * 4096) to be more "precise". I don't know > why we have all these different weights and why they are the way > they are - but it's a lot of apples and oranges we put together > in a magic number to compare ;) > > I prefer to do a minimal change now, but both floor and ceil work > for me, so if you prefer I can change (but as said, it would only > matter with the mixing with the other cost factors, and in unknown > ways since the desire is not spelled out). Ok as is then. Jakub ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2024-01-23 12:43 UTC | newest] Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2024-01-23 11:56 [PATCH] tree-optimization/113552 - fix num_call accounting in simd clone vectorization Richard Biener 2024-01-23 12:01 ` Jakub Jelinek 2024-01-23 12:03 ` Richard Biener 2024-01-23 12:21 ` Jakub Jelinek 2024-01-23 12:40 ` Richard Biener 2024-01-23 12:43 ` Jakub Jelinek
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