[Mesa-dev] [PATCH 071/133] nir: Add a fused multiply-add peephole
Jason Ekstrand
jason at jlekstrand.net
Mon Dec 15 22:05:21 PST 2014
---
src/glsl/Makefile.sources | 1 +
src/glsl/nir/nir.h | 1 +
src/glsl/nir/nir_opcodes.h | 1 +
src/glsl/nir/nir_opt_peephole_ffma.c | 191 +++++++++++++++++++++++++++++++
src/mesa/drivers/dri/i965/brw_fs_nir.cpp | 2 +
5 files changed, 196 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 38ffb85..31608dc 100644
--- a/src/glsl/Makefile.sources
+++ b/src/glsl/Makefile.sources
@@ -32,6 +32,7 @@ NIR_FILES = \
$(GLSL_SRCDIR)/nir/nir_opt_copy_propagate.c \
$(GLSL_SRCDIR)/nir/nir_opt_dce.c \
$(GLSL_SRCDIR)/nir/nir_opt_global_to_local.c \
+ $(GLSL_SRCDIR)/nir/nir_opt_peephole_ffma.c \
$(GLSL_SRCDIR)/nir/nir_opt_peephole_select.c \
$(GLSL_SRCDIR)/nir/nir_print.c \
$(GLSL_SRCDIR)/nir/nir_remove_dead_variables.c \
diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
index bc2280b..e20eb7c 100644
--- a/src/glsl/nir/nir.h
+++ b/src/glsl/nir/nir.h
@@ -1374,6 +1374,7 @@ bool nir_opt_dce_impl(nir_function_impl *impl);
bool nir_opt_dce(nir_shader *shader);
bool nir_opt_peephole_select(nir_shader *shader);
+bool nir_opt_peephole_ffma(nir_shader *shader);
#ifdef __cplusplus
} /* extern "C" */
diff --git a/src/glsl/nir/nir_opcodes.h b/src/glsl/nir/nir_opcodes.h
index 988f691..35d4634 100644
--- a/src/glsl/nir/nir_opcodes.h
+++ b/src/glsl/nir/nir_opcodes.h
@@ -307,6 +307,7 @@ BINOP_HORIZ(vec2, 2, nir_type_unsigned, 1, nir_type_unsigned, 1, nir_type_unsign
ARR(src1_size, src2_size, src3_size), \
ARR(nir_type_unsigned, nir_type_unsigned, nir_type_unsigned))
+/* fma(a, b, c) = (a * b) + c */
TRIOP(ffma, nir_type_float)
TRIOP(flrp, nir_type_float)
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..2c9b8e5
--- /dev/null
+++ b/src/glsl/nir/nir_opt_peephole_ffma.c
@@ -0,0 +1,191 @@
+/*
+ * 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_instr *add, unsigned idx)
+{
+ if (!add->src[idx].src.is_ssa)
+ return NULL;
+
+ /* We can't handle these in between the operations */
+ if (add->src[idx].negate || add->src[idx].abs)
+ return NULL;
+
+ nir_instr *instr = add->src[idx].src.ssa->parent_instr;
+ if (instr->type != nir_instr_type_alu)
+ return NULL;
+
+ nir_alu_instr *mul = nir_instr_as_alu(instr);
+ if (mul->op != nir_op_fmul)
+ return NULL;
+
+ /* Can't handle a saturate in between */
+ if (mul->dest.saturate)
+ return NULL;
+
+ /* We already know that the same source is not used twice in the add and
+ * we will assume valid use-def information, so this check is sufficient
+ */
+ if (mul->dest.dest.ssa.uses->entries > 1)
+ return NULL; /* Not the only use */
+
+ return mul;
+}
+
+/* Copies (and maybe swizzles) the given ALU source */
+static inline void
+copy_alu_src(void *mem_ctx, nir_alu_src *new_src, nir_alu_src old_src,
+ uint8_t *swizzle)
+{
+ new_src->src = nir_src_copy(old_src.src, mem_ctx);
+ new_src->abs = old_src.abs;
+ new_src->negate = old_src.negate;
+
+ if (swizzle == NULL) {
+ memcpy(new_src->swizzle, old_src.swizzle, sizeof old_src.swizzle);
+ } else {
+ for (int i = 0; i < 4; ++i) {
+ if (swizzle[i] < 4)
+ new_src->swizzle[i] = old_src.swizzle[swizzle[i]];
+ }
+ }
+}
+
+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"? */
+
+ /* 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.is_ssa && add->src[1].src.is_ssa &&
+ add->src[0].src.ssa == add->src[1].src.ssa)
+ continue;
+
+ nir_alu_instr *mul = get_mul_for_src(add, 0);
+ unsigned mul_src = 0;
+
+ if (mul == NULL) {
+ mul = get_mul_for_src(add, 1);
+ mul_src = 1;
+ }
+
+ if (mul == NULL)
+ continue;
+
+ 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;
+
+ copy_alu_src(state->mem_ctx, &ffma->src[0], mul->src[0],
+ add->src[mul_src].swizzle);
+ copy_alu_src(state->mem_ctx, &ffma->src[1], mul->src[1],
+ add->src[mul_src].swizzle);
+ copy_alu_src(state->mem_ctx, &ffma->src[2], add->src[1 - mul_src], NULL);
+
+ if (add->dest.dest.is_ssa) {
+ ffma->dest.dest.is_ssa = true;
+ nir_ssa_def_init(state->impl, &ffma->instr, &ffma->dest.dest.ssa,
+ add->dest.dest.ssa.num_components,
+ add->dest.dest.ssa.name);
+
+ nir_src ffma_dest_src = {
+ .is_ssa = true,
+ .ssa = &ffma->dest.dest.ssa,
+ };
+ nir_ssa_def_rewrite_uses(&add->dest.dest.ssa, ffma_dest_src,
+ state->mem_ctx);
+ } else {
+ ffma->dest.dest = nir_dest_copy(add->dest.dest, state->mem_ctx);
+ }
+
+ nir_instr_insert_before(&add->instr, &ffma->instr);
+ nir_instr_remove(&add->instr);
+ nir_instr_remove(&mul->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_dirty(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;
+}
diff --git a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
index b2c5863..b6720af 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
@@ -63,6 +63,8 @@ fs_visitor::emit_nir_code()
nir_validate_shader(nir);
nir_opt_peephole_select(nir);
nir_validate_shader(nir);
+ nir_opt_peephole_ffma(nir);
+ nir_validate_shader(nir);
nir_print_shader(nir, stderr);
nir_convert_from_ssa(nir);
--
2.2.0
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