/*
* 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.
*/
#include "brw_fs.h"
#include "brw_fs_live_variables.h"
#include "brw_cfg.h"
/** @file brw_fs_cmod_propagation.cpp
*
* Implements a pass that propagates the conditional modifier from a CMP x 0.0
* instruction into the instruction that generated x. For instance, in this
* sequence
*
* add(8) g70<1>F g69<8,8,1>F 4096F
* cmp.ge.f0(8) null g70<8,8,1>F 0F
*
* we can do the comparison as part of the ADD instruction directly:
*
* add.ge.f0(8) g70<1>F g69<8,8,1>F 4096F
*
* If there had been a use of the flag register and another CMP using g70
*
* add.ge.f0(8) g70<1>F g69<8,8,1>F 4096F
* (+f0) sel(8) g71<F> g72<8,8,1>F g73<8,8,1>F
* cmp.ge.f0(8) null g70<8,8,1>F 0F
*
* we can recognize that the CMP is generating the flag value that already
* exists and therefore remove the instruction.
*/
static bool
opt_cmod_propagation_local(bblock_t *block)
{
bool progress = false;
int ip = block->end_ip + 1;
foreach_inst_in_block_reverse_safe(fs_inst, inst, block) {
ip--;
if ((inst->opcode != BRW_OPCODE_AND &&
inst->opcode != BRW_OPCODE_CMP &&
inst->opcode != BRW_OPCODE_MOV) ||
inst->predicate != BRW_PREDICATE_NONE ||
!inst->dst.is_null() ||
inst->src[0].file != GRF ||
inst->src[0].abs)
continue;
/* Only an AND.NZ can be propagated. Many AND.Z instructions are
* generated (for ir_unop_not in fs_visitor::emit_bool_to_cond_code).
* Propagating those would require inverting the condition on the CMP.
* This changes both the flag value and the register destination of the
* CMP. That result may be used elsewhere, so we can't change its value
* on a whim.
*/
if (inst->opcode == BRW_OPCODE_AND &&
!(inst->src[1].is_one() &&
inst->conditional_mod == BRW_CONDITIONAL_NZ &&
!inst->src[0].negate))
continue;
if (inst->opcode == BRW_OPCODE_CMP && !inst->src[1].is_zero())
continue;
if (inst->opcode == BRW_OPCODE_MOV &&
inst->conditional_mod != BRW_CONDITIONAL_NZ)
continue;
bool read_flag = false;
foreach_inst_in_block_reverse_starting_from(fs_inst, scan_inst, inst,
block) {
if (scan_inst->overwrites_reg(inst->src[0])) {
if (scan_inst->is_partial_write() ||
scan_inst->dst.reg_offset != inst->src[0].reg_offset)
break;
/* CMP's result is the same regardless of dest type. */
if (inst->conditional_mod == BRW_CONDITIONAL_NZ &&
scan_inst->opcode == BRW_OPCODE_CMP &&
(inst->dst.type == BRW_REGISTER_TYPE_D ||
inst->dst.type == BRW_REGISTER_TYPE_UD)) {
inst->remove(block);
progress = true;
break;
}
/* If the AND wasn't handled by the previous case, it isn't safe
* to remove it.
*/
if (inst->opcode == BRW_OPCODE_AND)
break;
/* Comparisons operate differently for ints and floats */
if (scan_inst->dst.type != inst->dst.type &&
(scan_inst->dst.type == BRW_REGISTER_TYPE_F ||
inst->dst.type == BRW_REGISTER_TYPE_F))
break;
/* If the instruction generating inst's source also wrote the
* flag, and inst is doing a simple .nz comparison, then inst
* is redundant - the appropriate value is already in the flag
* register. Delete inst.
*/
if (inst->conditional_mod == BRW_CONDITIONAL_NZ &&
!inst->src[0].negate &&
scan_inst->writes_flag()) {
inst->remove(block);
progress = true;
break;
}
/* Otherwise, try propagating the conditional. */
enum brw_conditional_mod cond =
inst->src[0].negate ? brw_swap_cmod(inst->conditional_mod)
: inst->conditional_mod;
if (scan_inst->can_do_cmod() &&
((!read_flag && scan_inst->conditional_mod == BRW_CONDITIONAL_NONE) ||
scan_inst->conditional_mod == cond)) {
scan_inst->conditional_mod = cond;
inst->remove(block);
progress = true;
}
break;
}
if (scan_inst->writes_flag())
break;
read_flag = read_flag || scan_inst->reads_flag();
}
}
return progress;
}
bool
fs_visitor::opt_cmod_propagation()
{
bool progress = false;
foreach_block_reverse(block, cfg) {
progress = opt_cmod_propagation_local(block) || progress;
}
if (progress)
invalidate_live_intervals();
return progress;
}