:) agree to you, but as soon as you're a user who tries to introduce
vector code and face a bug in cost model you'd like to have a
workaround until the bug will be fixed and compiler will come to you
with new OS distribution, don't you?
I propose the following, yet SLP have to use a NULL as a loop info
which looks somewhat hacky.
Sergos
* common.opt: Added new option -fsimd-vect-cost-model
* tree-vectorizer.h (unlimited_cost_model): Interface update
to rely on particular loop info
* tree-vect-data-refs.c (vect_peeling_hash_insert): Update to
unlimited_cost_model call according to new interface
(vect_peeling_hash_choose_best_peeling): Ditto
(vect_enhance_data_refs_alignment): Ditto
* tree-vect-slp.c: Ditto
* tree-vect-loop.c (vect_estimate_min_profitable_iters): Ditto
plus issue a warning in case cost model overrides users' directive
diff --git a/gcc/common.opt b/gcc/common.opt
index d5971df..87b3b37 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -2296,6 +2296,10 @@ fvect-cost-model=
Common Joined RejectNegative Enum(vect_cost_model)
Var(flag_vect_cost_model) Init(VECT_COST_MODEL_DEFAULT)
Specifies the cost model for vectorization
+fsimd-vect-cost-model=
+Common Joined RejectNegative Enum(vect_cost_model)
Var(flag_simd_vect_cost_model) Init(VECT_COST_MODEL_UNLIMITED)
+Specifies the cost model for vectorization in loops marked with
#pragma omp simd
+
Enum
Name(vect_cost_model) Type(enum vect_cost_model) UnknownError(unknown
vectorizer cost model %qs)
diff --git a/gcc/tree-vect-data-refs.c b/gcc/tree-vect-data-refs.c
index 83d1f45..e26f704 100644
--- a/gcc/tree-vect-data-refs.c
+++ b/gcc/tree-vect-data-refs.c
@@ -1090,7 +1090,8 @@ vect_peeling_hash_insert (loop_vec_info
loop_vinfo, struct data_reference *dr,
*new_slot = slot;
}
- if (!supportable_dr_alignment && unlimited_cost_model ())
+ if (!supportable_dr_alignment
+ && unlimited_cost_model (LOOP_VINFO_LOOP (loop_vinfo)))
slot->count += VECT_MAX_COST;
}
@@ -1200,7 +1201,7 @@ vect_peeling_hash_choose_best_peeling
(loop_vec_info loop_vinfo,
res.peel_info.dr = NULL;
res.body_cost_vec = stmt_vector_for_cost ();
- if (!unlimited_cost_model ())
+ if (!unlimited_cost_model (LOOP_VINFO_LOOP (loop_vinfo)))
{
res.inside_cost = INT_MAX;
res.outside_cost = INT_MAX;
@@ -1429,7 +1430,7 @@ vect_enhance_data_refs_alignment (loop_vec_info
loop_vinfo)
vectorization factor.
We do this automtically for cost model, since we
calculate cost
for every peeling option. */
- if (unlimited_cost_model ())
+ if (unlimited_cost_model (LOOP_VINFO_LOOP (loop_vinfo)))
possible_npeel_number = vf /nelements;
/* Handle the aligned case. We may decide to align some other
@@ -1437,7 +1438,7 @@ vect_enhance_data_refs_alignment (loop_vec_info
loop_vinfo)
if (DR_MISALIGNMENT (dr) == 0)
{
npeel_tmp = 0;
- if (unlimited_cost_model ())
+ if (unlimited_cost_model (LOOP_VINFO_LOOP (loop_vinfo)))
possible_npeel_number++;
}
diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c
index 86ebbd2..be66172 100644
--- a/gcc/tree-vect-loop.c
+++ b/gcc/tree-vect-loop.c
@@ -2696,7 +2696,7 @@ vect_estimate_min_profitable_iters
(loop_vec_info loop_vinfo,
void *target_cost_data = LOOP_VINFO_TARGET_COST_DATA (loop_vinfo);
/* Cost model disabled. */
- if (unlimited_cost_model ())
+ if (unlimited_cost_model (LOOP_VINFO_LOOP (loop_vinfo)))
{
dump_printf_loc (MSG_NOTE, vect_location, "cost model disabled.\n");
*ret_min_profitable_niters = 0;
@@ -2929,6 +2929,11 @@ vect_estimate_min_profitable_iters
(loop_vec_info loop_vinfo,
/* vector version will never be profitable. */
else
{
+ if (LOOP_VINFO_LOOP (loop_vinfo)->force_vect)
+ {
+ pedwarn (vect_location, 0, "Vectorization did not happen
for the loop");
+ }
+
if (dump_enabled_p ())
dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
"cost model: the vector iteration cost = %d "
diff --git a/gcc/tree-vect-slp.c b/gcc/tree-vect-slp.c
index 247bdfd..4b25964 100644
--- a/gcc/tree-vect-slp.c
+++ b/gcc/tree-vect-slp.c
@@ -2171,7 +2171,7 @@ vect_slp_analyze_bb_1 (basic_block bb)
}
/* Cost model: check if the vectorization is worthwhile. */
- if (!unlimited_cost_model ()
+ if (!unlimited_cost_model (NULL)
&& !vect_bb_vectorization_profitable_p (bb_vinfo))
{
if (dump_enabled_p ())
diff --git a/gcc/tree-vectorizer.h b/gcc/tree-vectorizer.h
index a6c5b59..2916906 100644
--- a/gcc/tree-vectorizer.h
+++ b/gcc/tree-vectorizer.h
@@ -919,9 +919,12 @@ known_alignment_for_access_p (struct
data_reference *data_ref_info)
/* Return true if the vect cost model is unlimited. */
static inline bool
-unlimited_cost_model ()
+unlimited_cost_model (loop_p loop)
{
- return flag_vect_cost_model == VECT_COST_MODEL_UNLIMITED;
+ return (flag_vect_cost_model == VECT_COST_MODEL_UNLIMITED
+ || (loop != NULL
+ && loop->force_vect
+ && flag_simd_vect_cost_model == VECT_COST_MODEL_UNLIMITED));
}
/* Source location */
On Mon, Nov 18, 2013 at 7:13 PM, Richard Biener <rguent...@suse.de> wrote:
> On Mon, 18 Nov 2013, Sergey Ostanevich wrote:
>
>> I would agree that the example is just for the case cost model makes
>> correct estimation But how can we assure ourself that it won't have any
>> mistakes in the future?
>
> We call it bugs and not mistakes and we have bugzilla for it.
>
> Richard.
>
>> I believe it'll be Ok to introduce an extra flag as Jakub proposed for the
>> dedicated simd-forced vectorization to use unlimited cost model. This
>> can be default for -fopenmp or there should be a warning issued that
>> compiler overrides user's request of vectorization. In such a case user
>> can enforce vectorization (even with mentioned results :) with this
>> unlimited cost model for simd.
>>
>>
>>
>> On Fri, Nov 15, 2013 at 6:24 PM, Richard Biener <rguent...@suse.de> wrote:
>> > On Fri, 15 Nov 2013, Sergey Ostanevich wrote:
>> >
>> >> Richard,
>> >>
>> >> here's an example that causes trigger for the cost model.
>> >
>> > I hardly believe that (AVX2)
>> >
>> > .L9:
>> > vmovups (%rsi), %xmm3
>> > addl $1, %r8d
>> > addq $256, %rsi
>> > vinsertf128 $0x1, -240(%rsi), %ymm3, %ymm1
>> > vmovups -224(%rsi), %xmm3
>> > vinsertf128 $0x1, -208(%rsi), %ymm3, %ymm3
>> > vshufps $136, %ymm3, %ymm1, %ymm3
>> > vperm2f128 $3, %ymm3, %ymm3, %ymm2
>> > vshufps $68, %ymm2, %ymm3, %ymm1
>> > vshufps $238, %ymm2, %ymm3, %ymm2
>> > vmovups -192(%rsi), %xmm3
>> > vinsertf128 $1, %xmm2, %ymm1, %ymm2
>> > vinsertf128 $0x1, -176(%rsi), %ymm3, %ymm1
>> > vmovups -160(%rsi), %xmm3
>> > vinsertf128 $0x1, -144(%rsi), %ymm3, %ymm3
>> > vshufps $136, %ymm3, %ymm1, %ymm3
>> > vperm2f128 $3, %ymm3, %ymm3, %ymm1
>> > vshufps $68, %ymm1, %ymm3, %ymm4
>> > vshufps $238, %ymm1, %ymm3, %ymm1
>> > vmovups -128(%rsi), %xmm3
>> > vinsertf128 $1, %xmm1, %ymm4, %ymm1
>> > vshufps $136, %ymm1, %ymm2, %ymm1
>> > vperm2f128 $3, %ymm1, %ymm1, %ymm2
>> > vshufps $68, %ymm2, %ymm1, %ymm4
>> > vshufps $238, %ymm2, %ymm1, %ymm2
>> > vinsertf128 $0x1, -112(%rsi), %ymm3, %ymm1
>> > vmovups -96(%rsi), %xmm3
>> > vinsertf128 $1, %xmm2, %ymm4, %ymm4
>> > vinsertf128 $0x1, -80(%rsi), %ymm3, %ymm3
>> > vshufps $136, %ymm3, %ymm1, %ymm3
>> > vperm2f128 $3, %ymm3, %ymm3, %ymm2
>> > vshufps $68, %ymm2, %ymm3, %ymm1
>> > vshufps $238, %ymm2, %ymm3, %ymm2
>> > vmovups -64(%rsi), %xmm3
>> > vinsertf128 $1, %xmm2, %ymm1, %ymm2
>> > vinsertf128 $0x1, -48(%rsi), %ymm3, %ymm1
>> > vmovups -32(%rsi), %xmm3
>> > vinsertf128 $0x1, -16(%rsi), %ymm3, %ymm3
>> > cmpl %r8d, %edi
>> > vshufps $136, %ymm3, %ymm1, %ymm3
>> > vperm2f128 $3, %ymm3, %ymm3, %ymm1
>> > vshufps $68, %ymm1, %ymm3, %ymm5
>> > vshufps $238, %ymm1, %ymm3, %ymm1
>> > vinsertf128 $1, %xmm1, %ymm5, %ymm1
>> > vshufps $136, %ymm1, %ymm2, %ymm1
>> > vperm2f128 $3, %ymm1, %ymm1, %ymm2
>> > vshufps $68, %ymm2, %ymm1, %ymm3
>> > vshufps $238, %ymm2, %ymm1, %ymm2
>> > vinsertf128 $1, %xmm2, %ymm3, %ymm1
>> > vshufps $136, %ymm1, %ymm4, %ymm1
>> > vperm2f128 $3, %ymm1, %ymm1, %ymm2
>> > vshufps $68, %ymm2, %ymm1, %ymm3
>> > vshufps $238, %ymm2, %ymm1, %ymm2
>> > vinsertf128 $1, %xmm2, %ymm3, %ymm2
>> > vaddps %ymm2, %ymm0, %ymm0
>> > ja .L9
>> >
>> > is more efficient than
>> >
>> > .L3:
>> > vaddss (%rcx,%rax), %xmm0, %xmm0
>> > addq $32, %rax
>> > cmpq %rdx, %rax
>> > jne .L3
>> >
>> > ;)
>> >
>> >> As soon as
>> >> elemental functions will appear and we update the vectorizer so it can
>> >> accept
>> >> an elemental function inside the loop - we will have the same
>> >> situation as we have
>> >> it now: cost model will bail out with profitability estimation.
>> >
>> > Yes.
>> >
>> >> Still we have no chance to get info on how efficient the bar() function
>> >> when it
>> >> is in vector form.
>> >
>> > Well I assume you mean that the speedup when vectorizing the elemental
>> > will offset whatever wreckage we cause with vectorizing the rest of the
>> > statements. I'd say you can at least compare to unrolling by
>> > the vectorization factor, building the vector inputs to the elemental
>> > from scalars, distributing the vector result from the elemental to
>> > scalars.
>> >
>> >> I believe I should repeat: #pragma omp simd is intended for introduction
>> >> of an
>> >> instruction-level parallel region on developer's request, hence should
>> >> be treated
>> >> in same manner as #pragma omp parallel. Vectorizer cost model is an
>> >> obstacle
>> >> here, not a help.
>> >
>> > Surely not if there isn't an elemental call in it. With it the
>> > cost model of course will have not enough information to decide.
>> >
>> > But still, what's the difference to the case where we cannot vectorize
>> > the function? What happens if we cannot vectorize the elemental?
>> > Do we have to build scalar versions for all possible vector sizes?
>> >
>> > Richard.
>> >
>> >> Regards,
>> >> Sergos
>> >>
>> >>
>> >> On Fri, Nov 15, 2013 at 1:08 AM, Richard Biener <rguent...@suse.de> wrote:
>> >> > Sergey Ostanevich <sergos....@gmail.com> wrote:
>> >> >>this is only for the whole file? I mean to have a particular loop
>> >> >>vectorized in a
>> >> >>file while all others - up to compiler's cost model. is there such a
>> >> >>machinery?
>> >> >
>> >> > No, there is not.
>> >> >
>> >> > Richard.
>> >> >
>> >> >>Sergos
>> >> >>
>> >> >>On Thu, Nov 14, 2013 at 12:39 PM, Richard Biener <rguent...@suse.de>
>> >> >>wrote:
>> >> >>> On Wed, 13 Nov 2013, Sergey Ostanevich wrote:
>> >> >>>
>> >> >>>> I will get some tests.
>> >> >>>> As for cost analysis - simply consider the pragma as a request to
>> >> >>>> vectorize. How can I - as a developer - enforce it beyond the
>> >> >>pragma?
>> >> >>>
>> >> >>> You can disable the cost model via -fvect-cost-model=unlimited
>> >> >>>
>> >> >>> Richard.
>> >> >>>
>> >> >>>> On Wed, Nov 13, 2013 at 12:55 PM, Richard Biener <rguent...@suse.de>
>> >> >>wrote:
>> >> >>>> > On Tue, 12 Nov 2013, Sergey Ostanevich wrote:
>> >> >>>> >
>> >> >>>> >> The reason patch was in its original state is because we want
>> >> >>>> >> to notify user that his assumption of profitability may be wrong.
>> >> >>>> >> This is not a part of any spec and as far as I know ICC does not
>> >> >>>> >> notify user about the case. Still it can be a good hint for those
>> >> >>>> >> users who tries to get as much as possible performance.
>> >> >>>> >>
>> >> >>>> >> Richard's comment on the vectorization problems is about the same
>> >> >>-
>> >> >>>> >> to inform user that his attempt to force vectorization is failed.
>> >> >>>> >>
>> >> >>>> >> As for profitable or not - sometimes I believe it's impossible to
>> >> >>be
>> >> >>>> >> precise. For OMP we have case of a vector version of a function
>> >> >>>> >> and we have no chance to figure out whether it is profitable to
>> >> >>use
>> >> >>>> >> it or to loose it. If we can't map the loop for any vector length
>> >> >>>> >> other than 1 - I believe in this case we have to bail out and
>> >> >>report.
>> >> >>>> >> Is it about 'never profitable'?
>> >> >>>> >
>> >> >>>> > For example. I think we should report non-vectorized loops
>> >> >>>> > that are marked with force_vect anyway, with
>> >> >>-Wdisabled-optimization.
>> >> >>>> > Another case is that a loop may be profitable to vectorize if
>> >> >>>> > the ISA supports a gather instruction but otherwise not. Or if
>> >> >>the
>> >> >>>> > ISA supports efficient vector construction from N not loop
>> >> >>>> > invariant scalars (for vectorization of strided loads).
>> >> >>>> >
>> >> >>>> > Simply disregarding all of the cost analysis sounds completely
>> >> >>>> > bogus to me.
>> >> >>>> >
>> >> >>>> > I'd simply go for the diagnostic for now, not changing anything
>> >> >>else.
>> >> >>>> > We want to have a good understanding about why the cost model is
>> >> >>>> > so bad that we have to force to ignore it for #pragma simd - thus
>> >> >>we
>> >> >>>> > want testcases.
>> >> >>>> >
>> >> >>>> > Richard.
>> >> >>>> >
>> >> >>>> >>
>> >> >>>> >> On Tue, Nov 12, 2013 at 6:35 PM, Richard Biener
>> >> >><rguent...@suse.de> wrote:
>> >> >>>> >> > On 11/12/13 3:16 PM, Jakub Jelinek wrote:
>> >> >>>> >> >> On Tue, Nov 12, 2013 at 05:46:14PM +0400, Sergey Ostanevich
>> >> >>wrote:
>> >> >>>> >> >>> ivdep just substitutes all cross-iteration data analysis,
>> >> >>>> >> >>> nothing related to cost model. ICC does not cancel its
>> >> >>>> >> >>> cost model in case of #pragma ivdep
>> >> >>>> >> >>>
>> >> >>>> >> >>> as for the safelen - OMP standart treats it as a limitation
>> >> >>>> >> >>> for the vector length. this means if no safelen is present
>> >> >>>> >> >>> an arbitrary vector length can be used.
>> >> >>>> >> >>
>> >> >>>> >> >> I was talking about GCC loop->safelen, which is INT_MAX for
>> >> >>#pragma omp simd
>> >> >>>> >> >> without safelen clause or #pragma simd without vectorlength
>> >> >>clause.
>> >> >>>> >> >>
>> >> >>>> >> >>> so I believe loop->force_vect is the only trigger to
>> >> >>disregard
>> >> >>>> >> >>> the cost model
>> >> >>>> >> >>
>> >> >>>> >> >> Anyway, in that case I think the originally posted patch is
>> >> >>wrong,
>> >> >>>> >> >> if we want to treat force_vect as disregard all the cost model
>> >> >>and
>> >> >>>> >> >> force vectorization (well, the name of the field already kind
>> >> >>of suggest
>> >> >>>> >> >> that), then IMHO we should treat it the same as
>> >> >>-fvect-cost-model=unlimited
>> >> >>>> >> >> for those loops.
>> >> >>>> >> >
>> >> >>>> >> > Err - the user may have a specific sub-architecture in mind
>> >> >>when using
>> >> >>>> >> > #pragma simd, if you say we should completely ignore the cost
>> >> >>model
>> >> >>>> >> > then should we also sorry () if we cannot vectorize the loop
>> >> >>(either
>> >> >>>> >> > because of GCC deficiencies or lack of sub-target support)?
>> >> >>>> >> >
>> >> >>>> >> > That said, at least in the cases that the cost model says the
>> >> >>loop
>> >> >>>> >> > is never profitable to vectorize we should follow its advice.
>> >> >>>> >> >
>> >> >>>> >> > Richard.
>> >> >>>> >> >
>> >> >>>> >> >> Thus (untested):
>> >> >>>> >> >>
>> >> >>>> >> >> 2013-11-12 Jakub Jelinek <ja...@redhat.com>
>> >> >>>> >> >>
>> >> >>>> >> >> * tree-vect-loop.c (vect_estimate_min_profitable_iters):
>> >> >>Use
>> >> >>>> >> >> unlimited cost model also for force_vect loops.
>> >> >>>> >> >>
>> >> >>>> >> >> --- gcc/tree-vect-loop.c.jj 2013-11-12 12:09:40.000000000
>> >> >>+0100
>> >> >>>> >> >> +++ gcc/tree-vect-loop.c 2013-11-12 15:11:43.821404330
>> >> >>+0100
>> >> >>>> >> >> @@ -2702,7 +2702,7 @@ vect_estimate_min_profitable_iters (loop
>> >> >>>> >> >> void *target_cost_data = LOOP_VINFO_TARGET_COST_DATA
>> >> >>(loop_vinfo);
>> >> >>>> >> >>
>> >> >>>> >> >> /* Cost model disabled. */
>> >> >>>> >> >> - if (unlimited_cost_model ())
>> >> >>>> >> >> + if (unlimited_cost_model () || LOOP_VINFO_LOOP
>> >> >>(loop_vinfo)->force_vect)
>> >> >>>> >> >> {
>> >> >>>> >> >> dump_printf_loc (MSG_NOTE, vect_location, "cost model
>> >> >>disabled.\n");
>> >> >>>> >> >> *ret_min_profitable_niters = 0;
>> >> >>>> >> >>
>> >> >>>> >> >> Jakub
>> >> >>>> >> >>
>> >> >>>> >> >
>> >> >>>> >>
>> >> >>>> >>
>> >> >>>> >
>> >> >>>> > --
>> >> >>>> > Richard Biener <rguent...@suse.de>
>> >> >>>> > SUSE / SUSE Labs
>> >> >>>> > SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746
>> >> >>>> > GF: Jeff Hawn, Jennifer Guild, Felix Imend
>> >> >>>>
>> >> >>>>
>> >> >>>
>> >> >>> --
>> >> >>> Richard Biener <rguent...@suse.de>
>> >> >>> SUSE / SUSE Labs
>> >> >>> SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746
>> >> >>> GF: Jeff Hawn, Jennifer Guild, Felix Imend"orffer
>> >> >
>> >> >
>> >>
>> >
>> > --
>> > Richard Biener <rguent...@suse.de>
>> > SUSE / SUSE Labs
>> > SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746
>> > GF: Jeff Hawn, Jennifer Guild, Felix Imend"orffer
>>
>>
>
> --
> Richard Biener <rguent...@suse.de>
> SUSE / SUSE Labs
> SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746
> GF: Jeff Hawn, Jennifer Guild, Felix Imend"orffer
