[Mesa-dev] [PATCH 5/9] nir: Add a dedicated ffma peephole optimization
Jason Ekstrand
jason at jlekstrand.net
Mon Mar 23 20:13:05 PDT 2015
---
src/glsl/Makefile.sources | 1 +
src/glsl/nir/nir_opt_peephole_ffma.c | 220 +++++++++++++++++++++++++++++++++++
2 files changed, 221 insertions(+)
create mode 100644 src/glsl/nir/nir_opt_peephole_ffma.c
diff --git a/src/glsl/Makefile.sources b/src/glsl/Makefile.sources
index b876642..1685a05 100644
--- a/src/glsl/Makefile.sources
+++ b/src/glsl/Makefile.sources
@@ -47,6 +47,7 @@ NIR_FILES = \
nir/nir_opt_dce.c \
nir/nir_opt_gcm.c \
nir/nir_opt_global_to_local.c \
+ nir/nir_opt_peephole_ffma.c \
nir/nir_opt_peephole_select.c \
nir/nir_opt_remove_phis.c \
nir/nir_print.c \
diff --git a/src/glsl/nir/nir_opt_peephole_ffma.c b/src/glsl/nir/nir_opt_peephole_ffma.c
new file mode 100644
index 0000000..4674505
--- /dev/null
+++ b/src/glsl/nir/nir_opt_peephole_ffma.c
@@ -0,0 +1,220 @@
+/*
+ * Copyright © 2014 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 small peephole optimization that looks for a multiply that
+ * is only ever used in an add and replaces both with an fma.
+ */
+
+struct peephole_ffma_state {
+ void *mem_ctx;
+ nir_function_impl *impl;
+ bool progress;
+};
+
+static inline nir_alu_instr *
+get_mul_for_src(nir_alu_src *src, uint8_t swizzle[4], bool *negate, bool *abs)
+{
+ assert(src->src.is_ssa && !src->abs && !src->negate);
+
+ nir_instr *instr = src->src.ssa->parent_instr;
+ if (instr->type != nir_instr_type_alu)
+ return NULL;
+
+ nir_alu_instr *alu = nir_instr_as_alu(instr);
+ switch (alu->op) {
+ case nir_op_imov:
+ case nir_op_fmov:
+ alu = get_mul_for_src(&alu->src[0], swizzle, negate, abs);
+ break;
+
+ case nir_op_fneg:
+ alu = get_mul_for_src(&alu->src[0], swizzle, negate, abs);
+ *negate = !*negate;
+ break;
+
+ case nir_op_fabs:
+ alu = get_mul_for_src(&alu->src[0], swizzle, negate, abs);
+ *negate = false;
+ *abs = true;
+ break;
+
+ case nir_op_fmul:
+ break;
+
+ default:
+ return NULL;
+ }
+
+ if (!alu)
+ return NULL;
+
+ for (unsigned i = 0; i < 4; i++) {
+ if (!(alu->dest.write_mask & (1 << i)))
+ break;
+
+ swizzle[i] = swizzle[src->swizzle[i]];
+ }
+
+ return alu;
+}
+
+static bool
+nir_opt_peephole_ffma_block(nir_block *block, void *void_state)
+{
+ struct peephole_ffma_state *state = void_state;
+
+ nir_foreach_instr_safe(block, instr) {
+ if (instr->type != nir_instr_type_alu)
+ continue;
+
+ nir_alu_instr *add = nir_instr_as_alu(instr);
+ if (add->op != nir_op_fadd)
+ continue;
+
+ /* TODO: Maybe bail if this expression is considered "precise"? */
+
+ assert(add->src[0].src.is_ssa && add->src[1].src.is_ssa);
+
+ /* This, is the case a + a. We would rather handle this with an
+ * algebraic reduction than fuse it. Also, we want to only fuse
+ * things where the multiply is used only once and, in this case,
+ * it would be used twice by the same instruction.
+ */
+ if (add->src[0].src.ssa == add->src[1].src.ssa)
+ continue;
+
+ nir_alu_instr *mul;
+ uint8_t add_mul_src, swizzle[4];
+ bool negate, abs;
+ for (add_mul_src = 0; add_mul_src < 2; add_mul_src++) {
+ for (unsigned i = 0; i < 4; i++)
+ swizzle[i] = i;
+
+ negate = false;
+ abs = false;
+
+ mul = get_mul_for_src(&add->src[add_mul_src], swizzle, &negate, &abs);
+
+ if (mul != NULL)
+ break;
+ }
+
+ if (mul == NULL)
+ continue;
+
+ nir_ssa_def *mul_src[2];
+ mul_src[0]= mul->src[0].src.ssa;
+ mul_src[1]= mul->src[1].src.ssa;
+
+ if (abs) {
+ for (unsigned i = 0; i < 2; i++) {
+ nir_alu_instr *abs = nir_alu_instr_create(state->mem_ctx,
+ nir_op_fabs);
+ abs->src[0].src = nir_src_for_ssa(mul_src[i]);
+ nir_ssa_dest_init(&abs->instr, &abs->dest.dest,
+ mul_src[i]->num_components, NULL);
+ abs->dest.write_mask = (1 << mul_src[i]->num_components) - 1;
+ nir_instr_insert_before(&add->instr, &abs->instr);
+ mul_src[i] = &abs->dest.dest.ssa;
+ }
+ }
+
+ if (negate) {
+ nir_alu_instr *neg = nir_alu_instr_create(state->mem_ctx,
+ nir_op_fneg);
+ neg->src[0].src = nir_src_for_ssa(mul_src[0]);
+ nir_ssa_dest_init(&neg->instr, &neg->dest.dest,
+ mul_src[0]->num_components, NULL);
+ neg->dest.write_mask = (1 << mul_src[0]->num_components) - 1;
+ nir_instr_insert_before(&add->instr, &neg->instr);
+ mul_src[0] = &neg->dest.dest.ssa;
+ }
+
+ nir_alu_instr *ffma = nir_alu_instr_create(state->mem_ctx, nir_op_ffma);
+ ffma->dest.saturate = add->dest.saturate;
+ ffma->dest.write_mask = add->dest.write_mask;
+
+ for (unsigned i = 0; i < 2; i++) {
+ ffma->src[i].src = nir_src_for_ssa(mul_src[i]);
+ for (unsigned j = 0; j < add->dest.dest.ssa.num_components; j++)
+ ffma->src[i].swizzle[j] = mul->src[i].swizzle[swizzle[j]];
+ }
+ nir_alu_src_copy(&ffma->src[2], &add->src[1 - add_mul_src],
+ state->mem_ctx);
+
+ assert(add->dest.dest.is_ssa);
+
+ nir_ssa_dest_init(&ffma->instr, &ffma->dest.dest,
+ add->dest.dest.ssa.num_components,
+ add->dest.dest.ssa.name);
+ nir_ssa_def_rewrite_uses(&add->dest.dest.ssa,
+ nir_src_for_ssa(&ffma->dest.dest.ssa),
+ state->mem_ctx);
+
+ nir_instr_insert_before(&add->instr, &ffma->instr);
+ assert(add->dest.dest.ssa.uses->entries == 0);
+ nir_instr_remove(&add->instr);
+
+ state->progress = true;
+ }
+
+ return true;
+}
+
+static bool
+nir_opt_peephole_ffma_impl(nir_function_impl *impl)
+{
+ struct peephole_ffma_state state;
+
+ state.mem_ctx = ralloc_parent(impl);
+ state.impl = impl;
+ state.progress = false;
+
+ nir_foreach_block(impl, nir_opt_peephole_ffma_block, &state);
+
+ if (state.progress)
+ nir_metadata_preserve(impl, nir_metadata_block_index |
+ nir_metadata_dominance);
+
+ return state.progress;
+}
+
+bool
+nir_opt_peephole_ffma(nir_shader *shader)
+{
+ bool progress = false;
+
+ nir_foreach_overload(shader, overload) {
+ if (overload->impl)
+ progress |= nir_opt_peephole_ffma_impl(overload->impl);
+ }
+
+ return progress;
+}
--
2.3.3
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