[Mesa-dev] [PATCH 2/2] i965/fs: Add a local common subexpression elimination pass.
Ian Romanick
idr at freedesktop.org
Fri May 11 14:27:28 PDT 2012
On 05/10/2012 04:10 PM, Kenneth Graunke wrote:
> Total instructions: 18210 -> 17836
> 49/163 programs affected (30.1%)
> 12888 -> 12514 instructions in affected programs (2.9% reduction)
>
> This reduces Lightsmark's "Scale down filter" shader from 395
> instructions to 283, a whopping 28%. It also reduces register pressure
> significantly: the SIMD8 program now uses 29 registers instead of 101,
> giving us more than enough room for a SIMD16 program.
>
> Signed-off-by: Kenneth Graunke<kenneth at whitecape.org>
This looks like a pretty straight forward implementation of the
algorithm from the book.
Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>
> ---
> src/mesa/drivers/dri/i965/Makefile.sources | 1 +
> src/mesa/drivers/dri/i965/brw_fs.cpp | 1 +
> src/mesa/drivers/dri/i965/brw_fs.h | 4 +
> src/mesa/drivers/dri/i965/brw_fs_cse.cpp | 194 ++++++++++++++++++++++++++++
> 4 files changed, 200 insertions(+)
> create mode 100644 src/mesa/drivers/dri/i965/brw_fs_cse.cpp
>
> diff --git a/src/mesa/drivers/dri/i965/Makefile.sources b/src/mesa/drivers/dri/i965/Makefile.sources
> index c564d95..838e1d3 100644
> --- a/src/mesa/drivers/dri/i965/Makefile.sources
> +++ b/src/mesa/drivers/dri/i965/Makefile.sources
> @@ -115,6 +115,7 @@ i965_CXX_FILES = \
> brw_cubemap_normalize.cpp \
> brw_fs.cpp \
> brw_fs_cfg.cpp \
> + brw_fs_cse.cpp \
> brw_fs_emit.cpp \
> brw_fs_live_variables.cpp \
> brw_fs_visitor.cpp \
> diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
> index bcdedf0..47dfec2 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
> @@ -1681,6 +1681,7 @@ fs_visitor::run()
>
> progress = propagate_constants() || progress;
> progress = opt_algebraic() || progress;
> + progress = opt_cse() || progress;
> progress = register_coalesce() || progress;
> progress = compute_to_mrf() || progress;
> progress = dead_code_eliminate() || progress;
> diff --git a/src/mesa/drivers/dri/i965/brw_fs.h b/src/mesa/drivers/dri/i965/brw_fs.h
> index d4473a2..0a9b8aa 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs.h
> +++ b/src/mesa/drivers/dri/i965/brw_fs.h
> @@ -49,6 +49,8 @@ extern "C" {
> #include "glsl/glsl_types.h"
> #include "glsl/ir.h"
>
> +class fs_bblock;
> +
> enum register_file {
> BAD_FILE,
> ARF,
> @@ -507,6 +509,8 @@ public:
> void calculate_live_intervals();
> bool propagate_constants();
> bool opt_algebraic();
> + bool opt_cse();
> + bool opt_cse_local(fs_bblock *block, exec_list *aeb);
> bool register_coalesce();
> bool compute_to_mrf();
> bool dead_code_eliminate();
> diff --git a/src/mesa/drivers/dri/i965/brw_fs_cse.cpp b/src/mesa/drivers/dri/i965/brw_fs_cse.cpp
> new file mode 100644
> index 0000000..d7cab0b
> --- /dev/null
> +++ b/src/mesa/drivers/dri/i965/brw_fs_cse.cpp
> @@ -0,0 +1,194 @@
> +/*
> + * Copyright © 2012 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.
> + */
> +
> +#include "brw_fs.h"
> +#include "brw_fs_cfg.h"
> +
> +/** @file brw_fs_cse.cpp
> + *
> + * Support for local common subexpression elimination.
> + *
> + * See Muchnik's Advanced Compiler Design and Implementation, section
> + * 13.1 (p378).
> + */
> +
> +namespace {
> +struct aeb_entry : public exec_node {
> + /** The instruction that generates the expression value. */
> + fs_inst *generator;
> +
> + /** The temporary where the value is stored. */
> + fs_reg tmp;
> +};
> +}
> +
> +static bool
> +is_expression(const fs_inst *const inst)
> +{
> + switch (inst->opcode) {
> + case BRW_OPCODE_SEL:
> + case BRW_OPCODE_NOT:
> + case BRW_OPCODE_AND:
> + case BRW_OPCODE_OR:
> + case BRW_OPCODE_XOR:
> + case BRW_OPCODE_SHR:
> + case BRW_OPCODE_SHL:
> + case BRW_OPCODE_RSR:
> + case BRW_OPCODE_RSL:
> + case BRW_OPCODE_ASR:
> + case BRW_OPCODE_ADD:
> + case BRW_OPCODE_MUL:
> + case BRW_OPCODE_FRC:
> + case BRW_OPCODE_RNDU:
> + case BRW_OPCODE_RNDD:
> + case BRW_OPCODE_RNDE:
> + case BRW_OPCODE_RNDZ:
> + case BRW_OPCODE_LINE:
> + case BRW_OPCODE_PLN:
> + case BRW_OPCODE_MAD:
> + case FS_OPCODE_CINTERP:
> + case FS_OPCODE_LINTERP:
> + return true;
> + default:
> + return false;
> + }
> +}
> +
> +static bool
> +operands_match(fs_reg *xs, fs_reg *ys)
> +{
> + return xs[0].equals(ys[0])&& xs[1].equals(ys[1])&& xs[2].equals(ys[2]);
> +}
> +
> +bool
> +fs_visitor::opt_cse_local(fs_bblock *block, exec_list *aeb)
> +{
> + bool progress = false;
> +
> + void *mem_ctx = ralloc_context(this->mem_ctx);
> +
> + for (fs_inst *inst = block->start;
> + inst != block->end->next;
> + inst = (fs_inst *) inst->next) {
> +
> + /* Skip some cases. */
> + if (is_expression(inst)&& !inst->predicated&& inst->mlen == 0&&
> + !inst->force_uncompressed&& !inst->force_sechalf)
> + {
> + bool found = false;
> +
> + aeb_entry *entry;
> + foreach_list(entry_node, aeb) {
> + entry = (aeb_entry *) entry_node;
> +
> + /* Match current instruction's expression against those in AEB. */
> + if (inst->opcode == entry->generator->opcode&&
> + inst->saturate == entry->generator->saturate&&
> + operands_match(entry->generator->src, inst->src)) {
> +
> + found = true;
> + progress = true;
> + break;
> + }
> + }
> +
> + if (!found) {
> + /* Our first sighting of this expression. Create an entry. */
> + aeb_entry *entry = ralloc(mem_ctx, aeb_entry);
> + entry->tmp = reg_undef;
> + entry->generator = inst;
> + aeb->push_tail(entry);
> + } else {
> + /* This is at least our second sighting of this expression.
> + * If we don't have a temporary already, make one.
> + */
> + bool no_existing_temp = entry->tmp.file == BAD_FILE;
> + if (no_existing_temp) {
> + entry->tmp = fs_reg(this, glsl_type::float_type);
> + entry->tmp.type = inst->dst.type;
> +
> + fs_inst *copy = new(ralloc_parent(inst))
> + fs_inst(BRW_OPCODE_MOV, entry->generator->dst, entry->tmp);
> + entry->generator->insert_after(copy);
> + entry->generator->dst = entry->tmp;
> + }
> +
> + /* dest<- temp */
> + fs_inst *copy = new(ralloc_parent(inst))
> + fs_inst(BRW_OPCODE_MOV, inst->dst, entry->tmp);
> + inst->replace_with(copy);
> +
> + /* Appending an instruction may have changed our bblock end. */
> + if (inst == block->end) {
> + block->end = copy;
> + }
> +
> + /* Continue iteration with copy->next */
> + inst = copy;
> + }
> + }
> +
> + /* Kill all AEB entries that use the destination. */
> + int start_offset = inst->dst.reg_offset;
> + int end_offset = start_offset + inst->regs_written();
> +
> + foreach_list_safe(entry_node, aeb) {
> + aeb_entry *entry = (aeb_entry *)entry_node;
> +
> + for (int i = 0; i< 3; i++) {
> + if (entry->generator->src[i].file == inst->dst.file&&
> + entry->generator->src[i].reg == inst->dst.reg&&
> + entry->generator->src[i].reg_offset>= start_offset&&
> + entry->generator->src[i].reg_offset< end_offset) {
> + entry->remove();
> + ralloc_free(entry);
> + break;
> + }
> + }
> + }
> + }
> +
> + ralloc_free(mem_ctx);
> +
> + if (progress)
> + this->live_intervals_valid = false;
> +
> + return progress;
> +}
> +
> +bool
> +fs_visitor::opt_cse()
> +{
> + bool progress = false;
> +
> + fs_cfg cfg(this);
> +
> + for (int b = 0; b< cfg.num_blocks; b++) {
> + fs_bblock *block = cfg.blocks[b];
> + exec_list aeb;
> +
> + progress = opt_cse_local(block,&aeb) || progress;
> + }
> +
> + return progress;
> +}
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