[Mesa-dev] [PATCH 1/2] nir: add an optimization to remove useless phi nodes
Jason Ekstrand
jason at jlekstrand.net
Tue Feb 3 12:51:42 PST 2015
Reviewed-by: Jason Ekstrand <jason.ekstrand at intel.com>
Tested-by: Jason Ekstrand <jason.ekstrand at intel.com>
And here's the shader-db stats for the commit message:
total NIR instructions in shared programs: 2045293 -> 2041209 (-0.20%)
NIR instructions in affected programs: 126564 -> 122480 (-3.23%)
helped: 615
HURT: 0
total FS instructions in shared programs: 4321840 -> 4320392 (-0.03%)
FS instructions in affected programs: 24622 -> 23174 (-5.88%)
helped: 138
HURT: 0
On Mon, Feb 2, 2015 at 10:59 PM, Connor Abbott <cwabbott0 at gmail.com> wrote:
> On Tue, Feb 3, 2015 at 1:54 AM, Connor Abbott <cwabbott0 at gmail.com> wrote:
> > This removes phi nodes whose sources all point to the same thing.
> >
> > Only compile tested.
> >
> > Signed-off-by: Connor Abbott <cwabbott0 at gmail.com>
> > ---
> > src/glsl/Makefile.sources | 1 +
> > src/glsl/nir/nir.h | 2 +
> > src/glsl/nir/nir_opt_remove_phis.c | 111
> +++++++++++++++++++++++++++++++++++++
> > 3 files changed, 114 insertions(+)
> > create mode 100644 src/glsl/nir/nir_opt_remove_phis.c
> >
> > diff --git a/src/glsl/Makefile.sources b/src/glsl/Makefile.sources
> > index face22e..6d51c71 100644
> > --- a/src/glsl/Makefile.sources
> > +++ b/src/glsl/Makefile.sources
> > @@ -44,6 +44,7 @@ NIR_FILES = \
> > nir/nir_opt_dce.c \
> > nir/nir_opt_global_to_local.c \
> > nir/nir_opt_peephole_select.c \
> > + nir/nir_opt_remove_phis.c \
> > nir/nir_print.c \
> > nir/nir_remove_dead_variables.c \
> > nir/nir_search.c \
> > diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
> > index 98d2689..d1860d4 100644
> > --- a/src/glsl/nir/nir.h
> > +++ b/src/glsl/nir/nir.h
> > @@ -1559,6 +1559,8 @@ bool nir_opt_dce(nir_shader *shader);
> > bool nir_opt_peephole_select(nir_shader *shader);
> > bool nir_opt_peephole_ffma(nir_shader *shader);
> >
> > +bool nir_opt_remove_phis(nir_shader *shader);
> > +
> > #ifdef __cplusplus
> > } /* extern "C" */
> > #endif
> > diff --git a/src/glsl/nir/nir_opt_remove_phis.c
> b/src/glsl/nir/nir_opt_remove_phis.c
> > new file mode 100644
> > index 0000000..aec5dc01
> > --- /dev/null
> > +++ b/src/glsl/nir/nir_opt_remove_phis.c
> > @@ -0,0 +1,111 @@
> > +/*
> > + * Copyright © 2015 Connor Abbott
> > + *
> > + * 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:
> > + * Connor Abbott (cwabbott0 at gmail.com)
> > + *
> > + */
> > +
> > +#include "nir.h"
> > +
> > +/*
> > + * This is a pass for removing phi nodes that look like:
> > + * a = phi(b, b, b, ...)
> > + *
> > + * Note that we can't ignore undef sources here, or else we may create a
> > + * situation where the definition of b isn't dominated by its uses.
> We're
> > + * allowed to do this since the definition of b must dominate all of the
> > + * phi node's predecessors, which means it must dominate the phi node
> as well
> > + * as all of the phi node's uses. In essence, the phi node acts as a
> copy
> > + * instruction. b can't be another phi node in the same block, since
> the only
> > + * time when phi nodes can source other phi nodes defined in the same
> block is
> > + * at the loop header, and in that case one of the sources of the phi
> has to
> > + * be from before the loop and that source can't be b.
> > + */
> > +
> > +/* returns true if any progress was made */
>
> Gah, this shouldn't be there. Fixed locally.
>
> > +
> > +static bool
> > +remove_phis_block(nir_block *block, void *state)
> > +{
> > + bool *progress = state;
> > +
> > + void *mem_ctx = ralloc_parent(block);
> > +
> > + nir_foreach_instr_safe(block, instr) {
> > + if (instr->type != nir_instr_type_phi)
> > + break;
> > +
> > + nir_phi_instr *phi = nir_instr_as_phi(instr);
> > +
> > + nir_ssa_def *def = NULL;
> > + bool srcs_same = true;
> > +
> > + nir_foreach_phi_src(phi, src) {
> > + assert(src->src.is_ssa);
> > +
> > + if (def == NULL) {
> > + def = src->src.ssa;
> > + } else {
> > + if (src->src.ssa != def) {
> > + srcs_same = false;
> > + break;
> > + }
> > + }
> > + }
> > +
> > + if (!srcs_same)
> > + continue;
> > +
> > + assert(phi->dest.is_ssa);
> > + nir_ssa_def_rewrite_uses(&phi->dest.ssa, nir_src_for_ssa(def),
> > + mem_ctx);
> > + nir_instr_remove(instr);
> > +
> > + *progress = true;
> > + }
> > +
> > + return true;
> > +}
> > +
> > +static bool
> > +remove_phis_impl(nir_function_impl *impl)
> > +{
> > + bool progress = false;
> > +
> > + nir_foreach_block(impl, remove_phis_block, &progress);
> > +
> > + return progress;
> > +}
> > +
> > +bool
> > +nir_opt_remove_phis(nir_shader *shader)
> > +{
> > + bool progress = false;
> > +
> > + nir_foreach_overload(shader, overload)
> > + if (overload->impl)
> > + progress = remove_phis_impl(overload->impl) || progress;
> > +
> > + return progress;
> > +}
> > +
> > --
> > 2.1.0
> >
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