[Mesa-dev] [PATCH 2/3] nir/algebraic: support for power-of-two optimizations
Jason Ekstrand
jason at jlekstrand.net
Mon May 16 19:16:24 UTC 2016
On Mon, May 16, 2016 at 9:09 AM, Rob Clark <robdclark at gmail.com> wrote:
> On Mon, May 16, 2016 at 10:45 AM, Jason Ekstrand <jason at jlekstrand.net>
> wrote:
> >
> > On May 16, 2016 7:29 AM, "Rob Clark" <robdclark at gmail.com> wrote:
> >>
> >> On Sat, May 14, 2016 at 4:03 PM, Jason Ekstrand <jason at jlekstrand.net>
> >> wrote:
> >> >
> >> >
> >> > On Sat, May 14, 2016 at 12:20 PM, Rob Clark <robdclark at gmail.com>
> wrote:
> >> >>
> >> >> On Thu, May 12, 2016 at 10:55 PM, Jason Ekstrand <
> jason at jlekstrand.net>
> >> >> wrote:
> >> >> >
> >> >> >
> >> >> > On Tue, May 10, 2016 at 11:57 AM, Rob Clark <robdclark at gmail.com>
> >> >> > wrote:
> >> >> >>
> >> >> >> From: Rob Clark <robclark at freedesktop.org>
> >> >> >>
> >> >> >> Some optimizations, like converting integer multiply/divide into
> >> >> >> left/
> >> >> >> right shifts, have additional constraints on the search
> expression.
> >> >> >> Like requiring that a variable is a constant power of two.
> Support
> >> >> >> these cases by allowing a fxn name to be appended to the search
> var
> >> >> >> expression (ie. "a#32(is_power_of_two)").
> >> >> >>
> >> >> >> TODO update doc/comment explaining search var syntax
> >> >> >> TODO the eagle-eyed viewer might have noticed that this could also
> >> >> >> replace the existing const syntax (ie. "#a"). Not sure if we
> should
> >> >> >> keep that.. we could make it syntactic sugar (ie '#' automatically
> >> >> >> sets
> >> >> >> the cond fxn ptr to 'is_const') or just get rid of it entirely?
> >> >> >> Maybe
> >> >> >> that is a follow-on clean-up patch?
> >> >> >>
> >> >> >> Signed-off-by: Rob Clark <robclark at freedesktop.org>
> >> >> >> ---
> >> >> >> src/compiler/nir/nir_algebraic.py | 8 +++--
> >> >> >> src/compiler/nir/nir_opt_algebraic.py | 5 +++
> >> >> >> src/compiler/nir/nir_search.c | 3 ++
> >> >> >> src/compiler/nir/nir_search.h | 10 ++++++
> >> >> >> src/compiler/nir/nir_search_helpers.h | 66
> >> >> >> +++++++++++++++++++++++++++++++++++
> >> >> >> 5 files changed, 90 insertions(+), 2 deletions(-)
> >> >> >> create mode 100644 src/compiler/nir/nir_search_helpers.h
> >> >> >>
> >> >> >> diff --git a/src/compiler/nir/nir_algebraic.py
> >> >> >> b/src/compiler/nir/nir_algebraic.py
> >> >> >> index 285f853..19ac6ee 100644
> >> >> >> --- a/src/compiler/nir/nir_algebraic.py
> >> >> >> +++ b/src/compiler/nir/nir_algebraic.py
> >> >> >> @@ -76,6 +76,7 @@ class Value(object):
> >> >> >> return Constant(val, name_base)
> >> >> >>
> >> >> >> __template = mako.template.Template("""
> >> >> >> +#include "compiler/nir/nir_search_helpers.h"
> >> >> >> static const ${val.c_type} ${val.name} = {
> >> >> >> { ${val.type_enum}, ${val.bit_size} },
> >> >> >> % if isinstance(val, Constant):
> >> >> >> @@ -84,6 +85,7 @@ static const ${val.c_type} ${val.name} = {
> >> >> >> ${val.index}, /* ${val.var_name} */
> >> >> >> ${'true' if val.is_constant else 'false'},
> >> >> >> ${val.type() or 'nir_type_invalid' },
> >> >> >> + ${val.cond if val.cond else 'NULL'},
> >> >> >> % elif isinstance(val, Expression):
> >> >> >> ${'true' if val.inexact else 'false'},
> >> >> >> nir_op_${val.opcode},
> >> >> >> @@ -113,7 +115,7 @@ static const ${val.c_type} ${val.name} = {
> >> >> >> Variable=Variable,
> >> >> >> Expression=Expression)
> >> >> >>
> >> >> >> -_constant_re = re.compile(r"(?P<value>[^@]+)(?:@(?P<bits>\d+))?")
> >> >> >> +_constant_re =
> re.compile(r"(?P<value>[^@\(]+)(?:@(?P<bits>\d+))?")
> >> >> >
> >> >> >
> >> >> > Spurious change?
> >> >> >
> >> >>
> >> >> I thought it needed to avoid matching something like
> >> >> a(is_power_of_two).. but it seems to work with that hunk reverted so
> I
> >> >> guess I can drop it..
> >> >>
> >> >> >>
> >> >> >>
> >> >> >> class Constant(Value):
> >> >> >> def __init__(self, val, name):
> >> >> >> @@ -150,7 +152,8 @@ class Constant(Value):
> >> >> >> return "nir_type_float"
> >> >> >>
> >> >> >> _var_name_re = re.compile(r"(?P<const>#)?(?P<name>\w+)"
> >> >> >> -
> >> >> >> r"(?:@(?P<type>int|uint|bool|float)?(?P<bits>\d+)?)?")
> >> >> >> +
> >> >> >> r"(?:@(?P<type>int|uint|bool|float)?(?P<bits>\d+)?)?"
> >> >> >> + r"(?P<cond>\([^\)]+\))?")
> >> >> >>
> >> >> >> class Variable(Value):
> >> >> >> def __init__(self, val, name, varset):
> >> >> >> @@ -161,6 +164,7 @@ class Variable(Value):
> >> >> >>
> >> >> >> self.var_name = m.group('name')
> >> >> >> self.is_constant = m.group('const') is not None
> >> >> >> + self.cond = m.group('cond')
> >> >> >> self.required_type = m.group('type')
> >> >> >> self.bit_size = int(m.group('bits')) if m.group('bits')
> else
> >> >> >> 0
> >> >> >>
> >> >> >> diff --git a/src/compiler/nir/nir_opt_algebraic.py
> >> >> >> b/src/compiler/nir/nir_opt_algebraic.py
> >> >> >> index 0a95725..952a91a 100644
> >> >> >> --- a/src/compiler/nir/nir_opt_algebraic.py
> >> >> >> +++ b/src/compiler/nir/nir_opt_algebraic.py
> >> >> >> @@ -62,6 +62,11 @@ d = 'd'
> >> >> >> # constructed value should have that bit-size.
> >> >> >>
> >> >> >> optimizations = [
> >> >> >> +
> >> >> >> + (('imul', a, '#b at 32(is_power_of_two)'), ('ishl', a,
> ('find_lsb',
> >> >> >> b))),
> >> >> >> + (('udiv', a, '#b at 32(is_power_of_two)'), ('ushr', a,
> ('find_lsb',
> >> >> >> b))),
> >> >> >> + (('umod', a, '#b(is_power_of_two)'), ('iand', a, ('isub',
> b,
> >> >> >> 1))),
> >> >> >> +
> >> >> >> (('fneg', ('fneg', a)), a),
> >> >> >> (('ineg', ('ineg', a)), a),
> >> >> >> (('fabs', ('fabs', a)), ('fabs', a)),
> >> >> >> diff --git a/src/compiler/nir/nir_search.c
> >> >> >> b/src/compiler/nir/nir_search.c
> >> >> >> index 2c2fd92..b21fb2c 100644
> >> >> >> --- a/src/compiler/nir/nir_search.c
> >> >> >> +++ b/src/compiler/nir/nir_search.c
> >> >> >> @@ -127,6 +127,9 @@ match_value(const nir_search_value *value,
> >> >> >> nir_alu_instr *instr, unsigned src,
> >> >> >> instr->src[src].src.ssa->parent_instr->type !=
> >> >> >> nir_instr_type_load_const)
> >> >> >> return false;
> >> >> >>
> >> >> >> + if (var->cond && !var->cond(instr, src, num_components,
> >> >> >> new_swizzle))
> >> >> >> + return false;
> >> >> >> +
> >> >> >> if (var->type != nir_type_invalid) {
> >> >> >> if (instr->src[src].src.ssa->parent_instr->type !=
> >> >> >> nir_instr_type_alu)
> >> >> >> return false;
> >> >> >> diff --git a/src/compiler/nir/nir_search.h
> >> >> >> b/src/compiler/nir/nir_search.h
> >> >> >> index a500feb..f55d797 100644
> >> >> >> --- a/src/compiler/nir/nir_search.h
> >> >> >> +++ b/src/compiler/nir/nir_search.h
> >> >> >> @@ -68,6 +68,16 @@ typedef struct {
> >> >> >> * never match anything.
> >> >> >> */
> >> >> >> nir_alu_type type;
> >> >> >> +
> >> >> >> + /** Optional condition fxn ptr
> >> >> >> + *
> >> >> >> + * This is only allowed in search expressions, and allows
> >> >> >> additional
> >> >> >> + * constraints to be placed on the match. Typically used for
> >> >> >> 'is_constant'
> >> >> >> + * variables to require, for example, power-of-two in order
> for
> >> >> >> the
> >> >> >> search
> >> >> >> + * to match.
> >> >> >> + */
> >> >> >> + bool (*cond)(nir_alu_instr *instr, unsigned src,
> >> >> >> + unsigned num_components, const uint8_t *swizzle);
> >> >> >> } nir_search_variable;
> >> >> >>
> >> >> >> typedef struct {
> >> >> >> diff --git a/src/compiler/nir/nir_search_helpers.h
> >> >> >> b/src/compiler/nir/nir_search_helpers.h
> >> >> >> new file mode 100644
> >> >> >> index 0000000..8ed2ca0
> >> >> >> --- /dev/null
> >> >> >> +++ b/src/compiler/nir/nir_search_helpers.h
> >> >> >> @@ -0,0 +1,66 @@
> >> >> >> +/*
> >> >> >> + * Copyright © 2016 Red Hat
> >> >> >> + *
> >> >> >> + * Permission is hereby granted, free of charge, to any person
> >> >> >> obtaining
> >> >> >> a
> >> >> >> + * copy of this software and associated documentation files (the
> >> >> >> "Software"),
> >> >> >> + * to deal in the Software without restriction, including without
> >> >> >> limitation
> >> >> >> + * the rights to use, copy, modify, merge, publish, distribute,
> >> >> >> sublicense,
> >> >> >> + * and/or sell copies of the Software, and to permit persons to
> >> >> >> whom
> >> >> >> the
> >> >> >> + * Software is furnished to do so, subject to the following
> >> >> >> conditions:
> >> >> >> + *
> >> >> >> + * The above copyright notice and this permission notice
> (including
> >> >> >> the
> >> >> >> next
> >> >> >> + * paragraph) shall be included in all copies or substantial
> >> >> >> portions
> >> >> >> of
> >> >> >> the
> >> >> >> + * Software.
> >> >> >> + *
> >> >> >> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
> KIND,
> >> >> >> EXPRESS OR
> >> >> >> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
> >> >> >> MERCHANTABILITY,
> >> >> >> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO
> >> >> >> EVENT
> >> >> >> SHALL
> >> >> >> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
> >> >> >> DAMAGES
> >> >> >> OR
> >> >> >> OTHER
> >> >> >> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
> OTHERWISE,
> >> >> >> ARISING
> >> >> >> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
> >> >> >> OTHER
> >> >> >> DEALINGS
> >> >> >> + * IN THE SOFTWARE.
> >> >> >> + *
> >> >> >> + * Authors:
> >> >> >> + * Rob Clark <robclark at freedesktop.org>
> >> >> >> + */
> >> >> >> +
> >> >> >> +#ifndef _NIR_SEARCH_HELPERS_
> >> >> >> +#define _NIR_SEARCH_HELPERS_
> >> >> >> +
> >> >> >> +#include "nir.h"
> >> >> >> +
> >> >> >> +static inline bool
> >> >> >> +__is_power_of_two(unsigned int x)
> >> >> >> +{
> >> >> >> + return ((x != 0) && !(x & (x - 1)));
> >> >> >> +}
> >> >> >> +
> >> >> >> +static inline bool
> >> >> >> +is_power_of_two(nir_alu_instr *instr, unsigned src, unsigned
> >> >> >> num_components,
> >> >> >> + const uint8_t *swizzle)
> >> >> >> +{
> >> >> >> + nir_const_value *val =
> >> >> >> nir_src_as_const_value(instr->src[src].src);
> >> >> >> +
> >> >> >> + /* only constant src's: */
> >> >> >> + if (!val)
> >> >> >> + return false;
> >> >> >> +
> >> >> >> + for (unsigned i = 0; i < num_components; i++) {
> >> >> >> + switch (nir_op_infos[instr->op].input_types[src]) {
> >> >> >> + case nir_type_int:
> >> >> >> + if (!__is_power_of_two(val->i32[swizzle[i]]))
> >> >> >> + return false;
> >> >> >> + break;
> >> >> >> + case nir_type_uint:
> >> >> >> + if (!__is_power_of_two(val->u32[swizzle[i]]))
> >> >> >> + return false;
> >> >> >
> >> >> >
> >> >> > Your implementation of __is_power_of_two takes an unsigned.
> There's
> >> >> > no
> >> >> > benefit to splitting it into two cases and it just creates a false
> >> >> > distinction. If you do, you can probably inline the helper (I
> don't
> >> >> > care
> >> >> > much one way or the other on that).
> >> >>
> >> >> hmm, are you sure about negative PoT? Although possibly that should
> >> >> be '__is_power_of_two(ABS(val->i32[..])'?
> >> >
> >> >
> >> > I don't know off-hand whether or not it's correct for negative
> >> > power-of-two.
> >> > However, I do know that it does exactly the same thing in both cases
> >> > regardless of whether or not the first one is correct :-)
> >> > --Jason
> >>
> >> so, for the record, __is_power_of_two(ABS(val->i32[..])) seems to be
> >> the correct thing to do. That would let us add a (presumably
> >> optional) rule to lower idiv to ushr plus a multiply by the isign of
> >> each of the args..
> >
> > Unfortunately, idiv can never be lowered because -1 >> 1 == -1. Yeah,
> > that's annoying.
> >
> > Also, I don't think any of the optimizations you've added here works for
> > negative numbers without a sign-flip. We would need a pair of
> > optimizations: one for non-negative powers of two and one for negative.
>
> so pretty sure this isn't an issue, since (udiv, a,
> #b(is_power_of_two)) hits the nir_type_uint case in is_power_of_two()
> and doesn't recognize -2 (for example) as a PoT..
>
> possibly we could do a bit better, I think we'd have to split
> is_power_of_two() into is_neg_power_of_two() and
> is_pos_power_of_two()..
>
I like that plan
> BR,
> -R
>
> >> BR,
> >> -R
> >>
> >> >>
> >> >> BR,
> >> >> -R
> >> >>
> >> >> > All in all, this seems ok. The "(some_function)" syntax seems
> clunky
> >> >> > but I
> >> >> > can't come up with anything better off-hand. Let's just go with it
> >> >> > for
> >> >> > now
> >> >> > and we can always change it later.
> >> >> >
> >> >> > Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>
> >> >> >
> >> >> >>
> >> >> >> + break;
> >> >> >> + default:
> >> >> >> + return false;
> >> >> >> + }
> >> >> >> + }
> >> >> >> +
> >> >> >> + return true;
> >> >> >> +}
> >> >> >> +
> >> >> >> +#endif /* _NIR_SEARCH_ */
> >> >> >> --
> >> >> >> 2.5.5
> >> >> >>
> >> >> >
> >> >
> >> >
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/mesa-dev/attachments/20160516/312bf607/attachment-0001.html>
More information about the mesa-dev
mailing list