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

[Jason Ekstrand]

On Thu, May 12, 2016 at 8:12 PM, Matt Turner <mattst88 at gmail.com> 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+))?")
> >
> >  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"?
>

And "pointer" while we're at it?
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