[Mesa-dev] [PATCH v4 1/3] nir: Add a pass to lower vector phi nodes to scalar phi nodes

[Jason Ekstrand]

On Wed, Jan 28, 2015 at 4:28 PM, Ian Romanick <idr at freedesktop.org> wrote:

> On 01/27/2015 05:31 PM, Jason Ekstrand wrote:
> > v2 Jason Ekstrand <jason.ekstrand at intel.com>:
> >  - Add better comments
> >  - Use nir_ssa_dest_init and nir_src_for_ssa more places
> >  - Fix some void * casts
> >
> > v3 Jason Ekstrand <jason.ekstrand at intel.com>:
> >  - Rework the way we determine whether or not to sccalarize a phi node to
> >    make the recursion non-bogus
> >  - Treat load_const instructions as scalarizable
> > ---
> >  src/glsl/Makefile.sources               |   1 +
> >  src/glsl/nir/nir.h                      |   2 +
> >  src/glsl/nir/nir_lower_phis_to_scalar.c | 266
> ++++++++++++++++++++++++++++++++
> >  3 files changed, 269 insertions(+)
> >  create mode 100644 src/glsl/nir/nir_lower_phis_to_scalar.c
> >
> > diff --git a/src/glsl/Makefile.sources b/src/glsl/Makefile.sources
> > index face22e..bf6b70b 100644
> > --- a/src/glsl/Makefile.sources
> > +++ b/src/glsl/Makefile.sources
> > @@ -31,6 +31,7 @@ NIR_FILES = \
> >       nir/nir_lower_global_vars_to_local.c \
> >       nir/nir_lower_locals_to_regs.c \
> >       nir/nir_lower_io.c \
> > +     nir/nir_lower_phis_to_scalar.c \
> >       nir/nir_lower_samplers.cpp \
> >       nir/nir_lower_system_values.c \
> >       nir/nir_lower_to_source_mods.c \
> > diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
> > index 980fdd0..4f58eee 100644
> > --- a/src/glsl/nir/nir.h
> > +++ b/src/glsl/nir/nir.h
> > @@ -1526,6 +1526,8 @@ void nir_remove_dead_variables(nir_shader *shader);
> >  void nir_lower_vec_to_movs(nir_shader *shader);
> >  void nir_lower_alu_to_scalar(nir_shader *shader);
> >
> > +void nir_lower_phis_to_scalar(nir_shader *shader);
> > +
> >  void nir_lower_samplers(nir_shader *shader,
> >                          struct gl_shader_program *shader_program,
> >                          struct gl_program *prog);
> > diff --git a/src/glsl/nir/nir_lower_phis_to_scalar.c
> b/src/glsl/nir/nir_lower_phis_to_scalar.c
> > new file mode 100644
> > index 0000000..a94b8b0
> > --- /dev/null
> > +++ b/src/glsl/nir/nir_lower_phis_to_scalar.c
> > @@ -0,0 +1,266 @@
> > +/*
> > + * Copyright © 2015 Intel Corporation
> > + *
> > + * 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:
> > + *    Jason Ekstrand (jason at jlekstrand.net)
> > + *
> > + */
> > +
> > +#include "nir.h"
> > +
> > +/*
> > + * Implements a pass that lowers vector phi nodes to scalar phi nodes
> when
> > + * we don't think it will hurt anything.
> > + */
> > +
> > +struct lower_phis_to_scalar_state {
> > +   void *mem_ctx;
> > +   void *dead_ctx;
> > +
> > +   /* Hash table marking which phi nodes are scalarizable.  The key is
> > +    * pointers to phi instructions and the entry is either NULL for not
> > +    * scalarizable or non-null for scalarizable.
> > +    */
> > +   struct hash_table *phi_table;
> > +};
> > +
> > +static bool
> > +should_lower_phi(nir_phi_instr *phi, struct lower_phis_to_scalar_state
> *state);
> > +
> > +static bool
> > +is_phi_src_scalarizable(nir_phi_src *src,
> > +                        struct lower_phis_to_scalar_state *state)
> > +{
> > +   /* Don't know what to do with non-ssa sources */
> > +   if (!src->src.is_ssa)
> > +      return false;
> > +
> > +   nir_instr *src_instr = src->src.ssa->parent_instr;
> > +   switch (src_instr->type) {
> > +   case nir_instr_type_alu: {
> > +      nir_alu_instr *src_alu = nir_instr_as_alu(src_instr);
> > +
> > +      /* ALU operations with output_size == 0 should be scalarized.  We
> > +       * will also see a bunch of vecN operations from scalarizing ALU
> > +       * operations and, since they can easily be copy-propagated, they
> > +       * are ok too.
> > +       */
> > +      return nir_op_infos[src_alu->op].output_size == 0 ||
> > +             src_alu->op != nir_op_vec2 ||
> > +             src_alu->op != nir_op_vec3 ||
> > +             src_alu->op != nir_op_vec4;
>
> I don't think this logic is correct.  It will return true if src_alu->op
> is nir_op_vec2 because that's not nir_op_vec4.  Right?
>
> Bah!  Yeah, that's completely bogus.  That said, I don't think you're
looking at the latest version.
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