/*
* 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@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 bool
are_all_uses_fadd(nir_ssa_def *def)
{
if (!list_empty(&def->if_uses))
return false;
nir_foreach_use(def, use_src) {
nir_instr *use_instr = use_src->parent_instr;
if (use_instr->type != nir_instr_type_alu)
return false;
nir_alu_instr *use_alu = nir_instr_as_alu(use_instr);
switch (use_alu->op) {
case nir_op_fadd:
break; /* This one's ok */
case nir_op_imov:
case nir_op_fmov:
case nir_op_fneg:
case nir_op_fabs:
assert(use_alu
->dest.
dest.
is_ssa);
if (!are_all_uses_fadd(&use_alu->dest.dest.ssa))
return false;
break;
default:
return false;
}
}
return true;
}
static 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;
break;
case nir_op_fmul:
/* Only absorb a fmul into a ffma if the fmul is is only used in fadd
* operations. This prevents us from being too aggressive with our
* fusing which can actually lead to more instructions.
*/
if (!are_all_uses_fadd(&alu->dest.dest.ssa))
return NULL;
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];
for (add_mul_src = 0; add_mul_src < 2; add_mul_src++) {
for (unsigned i = 0; i < 4; i++)
swizzle[i] = i;
negate = 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;
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(list_empty
(&add
->dest.
dest.
ssa.
uses));
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;
}