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

[Matt Turner]

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+))?")
>
>  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

Can we write out "function"?