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/*
* Copyright © 2014 Broadcom
*
* 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.
*/
/**
* @file vc4_opt_copy_propagation.c
*
* This implements simple copy propagation for QIR without control flow.
*
* For each temp, it keeps a qreg of which source it was MOVed from, if it
* was. If we see that used later, we can just reuse the source value, since
* we know we don't have control flow, and we have SSA for our values so
* there's no killing to worry about.
*/
#include "vc4_qir.h"
static bool
is_copy_mov(struct qinst *inst)
{
if (!inst)
return false;
if (inst->op != QOP_MOV &&
inst->op != QOP_FMOV &&
inst->op != QOP_MMOV) {
return false;
}
if (inst->dst.file != QFILE_TEMP)
return false;
if (inst->src[0].file != QFILE_TEMP &&
inst->src[0].file != QFILE_UNIF) {
return false;
}
if (inst->dst.pack || inst->cond != QPU_COND_ALWAYS)
return false;
return true;
}
static bool
try_copy_prop(struct vc4_compile *c, struct qinst *inst, struct qinst **movs)
{
bool debug = false;
bool progress = false;
for (int i = 0; i < qir_get_nsrc(inst); i++) {
if (inst->src[i].file != QFILE_TEMP)
continue;
/* We have two ways of finding MOVs we can copy propagate
* from. One is if it's an SSA def: then we can reuse it from
* any block in the program, as long as its source is also an
* SSA def. Alternatively, if it's in the "movs" array
* tracked within the block, then we know the sources for it
* haven't been changed since we saw the instruction within
* our block.
*/
struct qinst *mov = movs[inst->src[i].index];
if (!mov) {
if (!is_copy_mov(c->defs[inst->src[i].index]))
continue;
mov = c->defs[inst->src[i].index];
if (mov->src[0].file == QFILE_TEMP &&
!c->defs[mov->src[0].index])
continue;
}
/* Mul rotation's source needs to be in an r0-r3 accumulator,
* so no uniforms or regfile-a/r4 unpacking allowed.
*/
if (inst->op == QOP_ROT_MUL &&
(mov->src[0].file != QFILE_TEMP ||
mov->src[0].pack))
continue;
uint8_t unpack;
if (mov->src[0].pack) {
/* Make sure that the meaning of the unpack
* would be the same between the two
* instructions.
*/
if (qir_is_float_input(inst) !=
qir_is_float_input(mov)) {
continue;
}
/* There's only one unpack field, so make sure
* this instruction doesn't already use it.
*/
bool already_has_unpack = false;
for (int j = 0; j < qir_get_nsrc(inst); j++) {
if (inst->src[j].pack)
already_has_unpack = true;
}
if (already_has_unpack)
continue;
/* A destination pack requires the PM bit to
* be set to a specific value already, which
* may be different from ours.
*/
if (inst->dst.pack)
continue;
unpack = mov->src[0].pack;
} else {
unpack = inst->src[i].pack;
}
if (debug) {
fprintf(stderr, "Copy propagate: ");
qir_dump_inst(c, inst);
fprintf(stderr, "\n");
}
inst->src[i] = mov->src[0];
inst->src[i].pack = unpack;
if (debug) {
fprintf(stderr, "to: ");
qir_dump_inst(c, inst);
fprintf(stderr, "\n");
}
progress = true;
}
return progress;
}
static void
apply_kills(struct vc4_compile *c, struct qinst **movs, struct qinst *inst)
{
if (inst->dst.file != QFILE_TEMP)
return;
for (int i = 0; i < c->num_temps; i++) {
if (movs[i] &&
(movs[i]->dst.index == inst->dst.index ||
(movs[i]->src[0].file == QFILE_TEMP &&
movs[i]->src[0].index == inst->dst.index))) {
movs[i] = NULL;
}
}
}
bool
qir_opt_copy_propagation(struct vc4_compile *c)
{
bool progress = false;
struct qinst **movs;
movs = ralloc_array(c, struct qinst *, c->num_temps);
if (!movs)
return false;
qir_for_each_block(block, c) {
/* The MOVs array tracks only available movs within the
* block.
*/
memset(movs, 0, sizeof(struct qinst *) * c->num_temps);
qir_for_each_inst(inst, block) {
progress = try_copy_prop(c, inst, movs) || progress;
apply_kills(c, movs, inst);
if (is_copy_mov(inst))
movs[inst->dst.index] = inst;
}
}
ralloc_free(movs);
return progress;
}
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