On Tue, Feb 3, 2015 at 1:54 AM, Connor Abbott <cwabbo...@gmail.com> wrote:
> This removes phi nodes whose sources all point to the same thing.
>
> Only compile tested.
>
> Signed-off-by: Connor Abbott <cwabbo...@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 (cwabbo...@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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