[Mesa-dev] [PATCH 2/3] nir/algebraic: support for power-of-two optimizations

Fri May 13 02:55:21 UTC 2016

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?

>
>  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).

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
>
>
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