[Mesa-dev] [PATCH 2/2] i965/fs: Add a local common subexpression elimination pass.
Kenneth Graunke
kenneth at whitecape.org
Thu May 10 16:10:15 PDT 2012
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>
---
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;
+}
--
1.7.10.1
More information about the mesa-dev
mailing list