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chromium / chromiumos / third_party / mesa / bf9d5ff47cba19d9243e35e7743508f6b449b5e8 / . / src / intel / compiler / brw_schedule_instructions.cpp
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/*
* Copyright © 2010 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:
* Eric Anholt <eric@anholt.net>
*
*/
#include "brw_fs.h"
#include "brw_fs_live_variables.h"
#include "brw_vec4.h"
#include "brw_cfg.h"
#include "brw_shader.h"
using namespace brw;
/** @file brw_fs_schedule_instructions.cpp
*
* List scheduling of FS instructions.
*
* The basic model of the list scheduler is to take a basic block,
* compute a DAG of the dependencies (RAW ordering with latency, WAW
* ordering with latency, WAR ordering), and make a list of the DAG heads.
* Heuristically pick a DAG head, then put all the children that are
* now DAG heads into the list of things to schedule.
*
* The heuristic is the important part. We're trying to be cheap,
* since actually computing the optimal scheduling is NP complete.
* What we do is track a "current clock". When we schedule a node, we
* update the earliest-unblocked clock time of its children, and
* increment the clock. Then, when trying to schedule, we just pick
* the earliest-unblocked instruction to schedule.
*
* Note that often there will be many things which could execute
* immediately, and there are a range of heuristic options to choose
* from in picking among those.
*/
static bool debug = false;
class instruction_scheduler;
class schedule_node : public exec_node
{
public:
schedule_node(backend_instruction *inst, instruction_scheduler *sched);
void set_latency_gen4();
void set_latency_gen7(bool is_haswell);
backend_instruction *inst;
schedule_node **children;
int *child_latency;
int child_count;
int parent_count;
int child_array_size;
int unblocked_time;
int latency;
/**
* Which iteration of pushing groups of children onto the candidates list
* this node was a part of.
*/
unsigned cand_generation;
/**
* This is the sum of the instruction's latency plus the maximum delay of
* its children, or just the issue_time if it's a leaf node.
*/
int delay;
/**
* Preferred exit node among the (direct or indirect) successors of this
* node. Among the scheduler nodes blocked by this node, this will be the
* one that may cause earliest program termination, or NULL if none of the
* successors is an exit node.
*/
schedule_node *exit;
};
/**
* Lower bound of the scheduling time after which one of the instructions
* blocked by this node may lead to program termination.
*
* exit_unblocked_time() determines a strict partial ordering relation '«' on
* the set of scheduler nodes as follows:
*
* n « m <-> exit_unblocked_time(n) < exit_unblocked_time(m)
*
* which can be used to heuristically order nodes according to how early they
* can unblock an exit node and lead to program termination.
*/
static inline int
exit_unblocked_time(const schedule_node *n)
{
return n->exit ? n->exit->unblocked_time : INT_MAX;
}
void
schedule_node::set_latency_gen4()
{
int chans = 8;
int math_latency = 22;
switch (inst->opcode) {
case SHADER_OPCODE_RCP:
this->latency = 1 * chans * math_latency;
break;
case SHADER_OPCODE_RSQ:
this->latency = 2 * chans * math_latency;
break;
case SHADER_OPCODE_INT_QUOTIENT:
case SHADER_OPCODE_SQRT:
case SHADER_OPCODE_LOG2:
/* full precision log. partial is 2. */
this->latency = 3 * chans * math_latency;
break;
case SHADER_OPCODE_INT_REMAINDER:
case SHADER_OPCODE_EXP2:
/* full precision. partial is 3, same throughput. */
this->latency = 4 * chans * math_latency;
break;
case SHADER_OPCODE_POW:
this->latency = 8 * chans * math_latency;
break;
case SHADER_OPCODE_SIN:
case SHADER_OPCODE_COS:
/* minimum latency, max is 12 rounds. */
this->latency = 5 * chans * math_latency;
break;
default:
this->latency = 2;
break;
}
}
void
schedule_node::set_latency_gen7(bool is_haswell)
{
switch (inst->opcode) {
case BRW_OPCODE_MAD:
/* 2 cycles
* (since the last two src operands are in different register banks):
* mad(8) g4<1>F g2.2<4,4,1>F.x g2<4,4,1>F.x g3.1<4,4,1>F.x { align16 WE_normal 1Q };
*
* 3 cycles on IVB, 4 on HSW
* (since the last two src operands are in the same register bank):
* mad(8) g4<1>F g2.2<4,4,1>F.x g2<4,4,1>F.x g2.1<4,4,1>F.x { align16 WE_normal 1Q };
*
* 18 cycles on IVB, 16 on HSW
* (since the last two src operands are in different register banks):
* mad(8) g4<1>F g2.2<4,4,1>F.x g2<4,4,1>F.x g3.1<4,4,1>F.x { align16 WE_normal 1Q };
* mov(8) null g4<4,5,1>F { align16 WE_normal 1Q };
*
* 20 cycles on IVB, 18 on HSW
* (since the last two src operands are in the same register bank):
* mad(8) g4<1>F g2.2<4,4,1>F.x g2<4,4,1>F.x g2.1<4,4,1>F.x { align16 WE_normal 1Q };
* mov(8) null g4<4,4,1>F { align16 WE_normal 1Q };
*/
/* Our register allocator doesn't know about register banks, so use the
* higher latency.
*/
latency = is_haswell ? 16 : 18;
break;
case BRW_OPCODE_LRP:
/* 2 cycles
* (since the last two src operands are in different register banks):
* lrp(8) g4<1>F g2.2<4,4,1>F.x g2<4,4,1>F.x g3.1<4,4,1>F.x { align16 WE_normal 1Q };
*
* 3 cycles on IVB, 4 on HSW
* (since the last two src operands are in the same register bank):
* lrp(8) g4<1>F g2.2<4,4,1>F.x g2<4,4,1>F.x g2.1<4,4,1>F.x { align16 WE_normal 1Q };
*
* 16 cycles on IVB, 14 on HSW
* (since the last two src operands are in different register banks):
* lrp(8) g4<1>F g2.2<4,4,1>F.x g2<4,4,1>F.x g3.1<4,4,1>F.x { align16 WE_normal 1Q };
* mov(8) null g4<4,4,1>F { align16 WE_normal 1Q };
*
* 16 cycles
* (since the last two src operands are in the same register bank):
* lrp(8) g4<1>F g2.2<4,4,1>F.x g2<4,4,1>F.x g2.1<4,4,1>F.x { align16 WE_normal 1Q };
* mov(8) null g4<4,4,1>F { align16 WE_normal 1Q };
*/
/* Our register allocator doesn't know about register banks, so use the
* higher latency.
*/
latency = 14;
break;
case SHADER_OPCODE_RCP:
case SHADER_OPCODE_RSQ:
case SHADER_OPCODE_SQRT:
case SHADER_OPCODE_LOG2:
case SHADER_OPCODE_EXP2:
case SHADER_OPCODE_SIN:
case SHADER_OPCODE_COS:
/* 2 cycles:
* math inv(8) g4<1>F g2<0,1,0>F null { align1 WE_normal 1Q };
*
* 18 cycles:
* math inv(8) g4<1>F g2<0,1,0>F null { align1 WE_normal 1Q };
* mov(8) null g4<8,8,1>F { align1 WE_normal 1Q };
*
* Same for exp2, log2, rsq, sqrt, sin, cos.
*/
latency = is_haswell ? 14 : 16;
break;
case SHADER_OPCODE_POW:
/* 2 cycles:
* math pow(8) g4<1>F g2<0,1,0>F g2.1<0,1,0>F { align1 WE_normal 1Q };
*
* 26 cycles:
* math pow(8) g4<1>F g2<0,1,0>F g2.1<0,1,0>F { align1 WE_normal 1Q };
* mov(8) null g4<8,8,1>F { align1 WE_normal 1Q };
*/
latency = is_haswell ? 22 : 24;
break;
case SHADER_OPCODE_TEX:
case SHADER_OPCODE_TXD:
case SHADER_OPCODE_TXF:
case SHADER_OPCODE_TXF_LZ:
case SHADER_OPCODE_TXL:
case SHADER_OPCODE_TXL_LZ:
/* 18 cycles:
* mov(8) g115<1>F 0F { align1 WE_normal 1Q };
* mov(8) g114<1>F 0F { align1 WE_normal 1Q };
* send(8) g4<1>UW g114<8,8,1>F
* sampler (10, 0, 0, 1) mlen 2 rlen 4 { align1 WE_normal 1Q };
*
* 697 +/-49 cycles (min 610, n=26):
* mov(8) g115<1>F 0F { align1 WE_normal 1Q };
* mov(8) g114<1>F 0F { align1 WE_normal 1Q };
* send(8) g4<1>UW g114<8,8,1>F
* sampler (10, 0, 0, 1) mlen 2 rlen 4 { align1 WE_normal 1Q };
* mov(8) null g4<8,8,1>F { align1 WE_normal 1Q };
*
* So the latency on our first texture load of the batchbuffer takes
* ~700 cycles, since the caches are cold at that point.
*
* 840 +/- 92 cycles (min 720, n=25):
* mov(8) g115<1>F 0F { align1 WE_normal 1Q };
* mov(8) g114<1>F 0F { align1 WE_normal 1Q };
* send(8) g4<1>UW g114<8,8,1>F
* sampler (10, 0, 0, 1) mlen 2 rlen 4 { align1 WE_normal 1Q };
* mov(8) null g4<8,8,1>F { align1 WE_normal 1Q };
* send(8) g4<1>UW g114<8,8,1>F
* sampler (10, 0, 0, 1) mlen 2 rlen 4 { align1 WE_normal 1Q };
* mov(8) null g4<8,8,1>F { align1 WE_normal 1Q };
*
* On the second load, it takes just an extra ~140 cycles, and after
* accounting for the 14 cycles of the MOV's latency, that makes ~130.
*
* 683 +/- 49 cycles (min = 602, n=47):
* mov(8) g115<1>F 0F { align1 WE_normal 1Q };
* mov(8) g114<1>F 0F { align1 WE_normal 1Q };
* send(8) g4<1>UW g114<8,8,1>F
* sampler (10, 0, 0, 1) mlen 2 rlen 4 { align1 WE_normal 1Q };
* send(8) g50<1>UW g114<8,8,1>F
* sampler (10, 0, 0, 1) mlen 2 rlen 4 { align1 WE_normal 1Q };
* mov(8) null g4<8,8,1>F { align1 WE_normal 1Q };
*
* The unit appears to be pipelined, since this matches up with the
* cache-cold case, despite there being two loads here. If you replace
* the g4 in the MOV to null with g50, it's still 693 +/- 52 (n=39).
*
* So, take some number between the cache-hot 140 cycles and the
* cache-cold 700 cycles. No particular tuning was done on this.
*
* I haven't done significant testing of the non-TEX opcodes. TXL at
* least looked about the same as TEX.
*/
latency = 200;
break;
case SHADER_OPCODE_TXS:
/* Testing textureSize(sampler2D, 0), one load was 420 +/- 41
* cycles (n=15):
* mov(8) g114<1>UD 0D { align1 WE_normal 1Q };
* send(8) g6<1>UW g114<8,8,1>F
* sampler (10, 0, 10, 1) mlen 1 rlen 4 { align1 WE_normal 1Q };
* mov(16) g6<1>F g6<8,8,1>D { align1 WE_normal 1Q };
*
*
* Two loads was 535 +/- 30 cycles (n=19):
* mov(16) g114<1>UD 0D { align1 WE_normal 1H };
* send(16) g6<1>UW g114<8,8,1>F
* sampler (10, 0, 10, 2) mlen 2 rlen 8 { align1 WE_normal 1H };
* mov(16) g114<1>UD 0D { align1 WE_normal 1H };
* mov(16) g6<1>F g6<8,8,1>D { align1 WE_normal 1H };
* send(16) g8<1>UW g114<8,8,1>F
* sampler (10, 0, 10, 2) mlen 2 rlen 8 { align1 WE_normal 1H };
* mov(16) g8<1>F g8<8,8,1>D { align1 WE_normal 1H };
* add(16) g6<1>F g6<8,8,1>F g8<8,8,1>F { align1 WE_normal 1H };
*
* Since the only caches that should matter are just the
* instruction/state cache containing the surface state, assume that we
* always have hot caches.
*/
latency = 100;
break;
case FS_OPCODE_VARYING_PULL_CONSTANT_LOAD_GEN4:
case FS_OPCODE_VARYING_PULL_CONSTANT_LOAD_GEN7:
case FS_OPCODE_UNIFORM_PULL_CONSTANT_LOAD:
case FS_OPCODE_UNIFORM_PULL_CONSTANT_LOAD_GEN7:
case VS_OPCODE_PULL_CONSTANT_LOAD:
/* testing using varying-index pull constants:
*
* 16 cycles:
* mov(8) g4<1>D g2.1<0,1,0>F { align1 WE_normal 1Q };
* send(8) g4<1>F g4<8,8,1>D
* data (9, 2, 3) mlen 1 rlen 1 { align1 WE_normal 1Q };
*
* ~480 cycles:
* mov(8) g4<1>D g2.1<0,1,0>F { align1 WE_normal 1Q };
* send(8) g4<1>F g4<8,8,1>D
* data (9, 2, 3) mlen 1 rlen 1 { align1 WE_normal 1Q };
* mov(8) null g4<8,8,1>F { align1 WE_normal 1Q };
*
* ~620 cycles:
* mov(8) g4<1>D g2.1<0,1,0>F { align1 WE_normal 1Q };
* send(8) g4<1>F g4<8,8,1>D
* data (9, 2, 3) mlen 1 rlen 1 { align1 WE_normal 1Q };
* mov(8) null g4<8,8,1>F { align1 WE_normal 1Q };
* send(8) g4<1>F g4<8,8,1>D
* data (9, 2, 3) mlen 1 rlen 1 { align1 WE_normal 1Q };
* mov(8) null g4<8,8,1>F { align1 WE_normal 1Q };
*
* So, if it's cache-hot, it's about 140. If it's cache cold, it's
* about 460. We expect to mostly be cache hot, so pick something more
* in that direction.
*/
latency = 200;
break;
case SHADER_OPCODE_GEN7_SCRATCH_READ:
/* Testing a load from offset 0, that had been previously written:
*
* send(8) g114<1>UW g0<8,8,1>F data (0, 0, 0) mlen 1 rlen 1 { align1 WE_normal 1Q };
* mov(8) null g114<8,8,1>F { align1 WE_normal 1Q };
*
* The cycles spent seemed to be grouped around 40-50 (as low as 38),
* then around 140. Presumably this is cache hit vs miss.
*/
latency = 50;
break;
case SHADER_OPCODE_UNTYPED_ATOMIC:
case SHADER_OPCODE_TYPED_ATOMIC:
/* Test code:
* mov(8) g112<1>ud 0x00000000ud { align1 WE_all 1Q };
* mov(1) g112.7<1>ud g1.7<0,1,0>ud { align1 WE_all };
* mov(8) g113<1>ud 0x00000000ud { align1 WE_normal 1Q };
* send(8) g4<1>ud g112<8,8,1>ud
* data (38, 5, 6) mlen 2 rlen 1 { align1 WE_normal 1Q };
*
* Running it 100 times as fragment shader on a 128x128 quad
* gives an average latency of 13867 cycles per atomic op,
* standard deviation 3%. Note that this is a rather
* pessimistic estimate, the actual latency in cases with few
* collisions between threads and favorable pipelining has been
* seen to be reduced by a factor of 100.
*/
latency = 14000;
break;
case SHADER_OPCODE_UNTYPED_SURFACE_READ:
case SHADER_OPCODE_UNTYPED_SURFACE_WRITE:
case SHADER_OPCODE_TYPED_SURFACE_READ:
case SHADER_OPCODE_TYPED_SURFACE_WRITE:
/* Test code:
* mov(8) g112<1>UD 0x00000000UD { align1 WE_all 1Q };
* mov(1) g112.7<1>UD g1.7<0,1,0>UD { align1 WE_all };
* mov(8) g113<1>UD 0x00000000UD { align1 WE_normal 1Q };
* send(8) g4<1>UD g112<8,8,1>UD
* data (38, 6, 5) mlen 2 rlen 1 { align1 WE_normal 1Q };
* .
* . [repeats 8 times]
* .
* mov(8) g112<1>UD 0x00000000UD { align1 WE_all 1Q };
* mov(1) g112.7<1>UD g1.7<0,1,0>UD { align1 WE_all };
* mov(8) g113<1>UD 0x00000000UD { align1 WE_normal 1Q };
* send(8) g4<1>UD g112<8,8,1>UD
* data (38, 6, 5) mlen 2 rlen 1 { align1 WE_normal 1Q };
*
* Running it 100 times as fragment shader on a 128x128 quad
* gives an average latency of 583 cycles per surface read,
* standard deviation 0.9%.
*/
latency = is_haswell ? 300 : 600;
break;
default:
/* 2 cycles:
* mul(8) g4<1>F g2<0,1,0>F 0.5F { align1 WE_normal 1Q };
*
* 16 cycles:
* mul(8) g4<1>F g2<0,1,0>F 0.5F { align1 WE_normal 1Q };
* mov(8) null g4<8,8,1>F { align1 WE_normal 1Q };
*/
latency = 14;
break;
}
}
class instruction_scheduler {
public:
instruction_scheduler(backend_shader *s, int grf_count,
int hw_reg_count, int block_count,
instruction_scheduler_mode mode)
{
this->bs = s;
this->mem_ctx = ralloc_context(NULL);
this->grf_count = grf_count;
this->hw_reg_count = hw_reg_count;
this->instructions.make_empty();
this->instructions_to_schedule = 0;
this->post_reg_alloc = (mode == SCHEDULE_POST);
this->mode = mode;
if (!post_reg_alloc) {
this->reg_pressure_in = rzalloc_array(mem_ctx, int, block_count);
this->livein = ralloc_array(mem_ctx, BITSET_WORD *, block_count);
for (int i = 0; i < block_count; i++)
this->livein[i] = rzalloc_array(mem_ctx, BITSET_WORD,
BITSET_WORDS(grf_count));
this->liveout = ralloc_array(mem_ctx, BITSET_WORD *, block_count);
for (int i = 0; i < block_count; i++)
this->liveout[i] = rzalloc_array(mem_ctx, BITSET_WORD,
BITSET_WORDS(grf_count));
this->hw_liveout = ralloc_array(mem_ctx, BITSET_WORD *, block_count);
for (int i = 0; i < block_count; i++)
this->hw_liveout[i] = rzalloc_array(mem_ctx, BITSET_WORD,
BITSET_WORDS(hw_reg_count));
this->written = rzalloc_array(mem_ctx, bool, grf_count);
this->reads_remaining = rzalloc_array(mem_ctx, int, grf_count);
this->hw_reads_remaining = rzalloc_array(mem_ctx, int, hw_reg_count);
} else {
this->reg_pressure_in = NULL;
this->livein = NULL;
this->liveout = NULL;
this->hw_liveout = NULL;
this->written = NULL;
this->reads_remaining = NULL;
this->hw_reads_remaining = NULL;
}
}
~instruction_scheduler()
{
ralloc_free(this->mem_ctx);
}
void add_barrier_deps(schedule_node *n);
void add_dep(schedule_node *before, schedule_node *after, int latency);
void add_dep(schedule_node *before, schedule_node *after);
void run(cfg_t *cfg);
void add_insts_from_block(bblock_t *block);
void compute_delays();
void compute_exits();
virtual void calculate_deps() = 0;
virtual schedule_node *choose_instruction_to_schedule() = 0;
/**
* Returns how many cycles it takes the instruction to issue.
*
* Instructions in gen hardware are handled one simd4 vector at a time,
* with 1 cycle per vector dispatched. Thus SIMD8 pixel shaders take 2
* cycles to dispatch and SIMD16 (compressed) instructions take 4.
*/
virtual int issue_time(backend_instruction *inst) = 0;
virtual void count_reads_remaining(backend_instruction *inst) = 0;
virtual void setup_liveness(cfg_t *cfg) = 0;
virtual void update_register_pressure(backend_instruction *inst) = 0;
virtual int get_register_pressure_benefit(backend_instruction *inst) = 0;
void schedule_instructions(bblock_t *block);
void *mem_ctx;
bool post_reg_alloc;
int instructions_to_schedule;
int grf_count;
int hw_reg_count;
int reg_pressure;
int block_idx;
exec_list instructions;
backend_shader *bs;
instruction_scheduler_mode mode;
/*
* The register pressure at the beginning of each basic block.
*/
int *reg_pressure_in;
/*
* The virtual GRF's whose range overlaps the beginning of each basic block.
*/
BITSET_WORD **livein;
/*
* The virtual GRF's whose range overlaps the end of each basic block.
*/
BITSET_WORD **liveout;
/*
* The hardware GRF's whose range overlaps the end of each basic block.
*/
BITSET_WORD **hw_liveout;
/*
* Whether we've scheduled a write for this virtual GRF yet.
*/
bool *written;
/*
* How many reads we haven't scheduled for this virtual GRF yet.
*/
int *reads_remaining;
/*
* How many reads we haven't scheduled for this hardware GRF yet.
*/
int *hw_reads_remaining;
};
class fs_instruction_scheduler : public instruction_scheduler
{
public:
fs_instruction_scheduler(fs_visitor *v, int grf_count, int hw_reg_count,
int block_count,
instruction_scheduler_mode mode);
void calculate_deps();
bool is_compressed(fs_inst *inst);
schedule_node *choose_instruction_to_schedule();
int issue_time(backend_instruction *inst);
fs_visitor *v;
void count_reads_remaining(backend_instruction *inst);
void setup_liveness(cfg_t *cfg);
void update_register_pressure(backend_instruction *inst);
int get_register_pressure_benefit(backend_instruction *inst);
};
fs_instruction_scheduler::fs_instruction_scheduler(fs_visitor *v,
int grf_count, int hw_reg_count,
int block_count,
instruction_scheduler_mode mode)
: instruction_scheduler(v, grf_count, hw_reg_count, block_count, mode),
v(v)
{
}
static bool
is_src_duplicate(fs_inst *inst, int src)
{
for (int i = 0; i < src; i++)
if (inst->src[i].equals(inst->src[src]))
return true;
return false;
}
void
fs_instruction_scheduler::count_reads_remaining(backend_instruction *be)
{
fs_inst *inst = (fs_inst *)be;
if (!reads_remaining)
return;
for (int i = 0; i < inst->sources; i++) {
if (is_src_duplicate(inst, i))
continue;
if (inst->src[i].file == VGRF) {
reads_remaining[inst->src[i].nr]++;
} else if (inst->src[i].file == FIXED_GRF) {
if (inst->src[i].nr >= hw_reg_count)
continue;
for (unsigned j = 0; j < regs_read(inst, i); j++)
hw_reads_remaining[inst->src[i].nr + j]++;
}
}
}
void
fs_instruction_scheduler::setup_liveness(cfg_t *cfg)
{
/* First, compute liveness on a per-GRF level using the in/out sets from
* liveness calculation.
*/
for (int block = 0; block < cfg->num_blocks; block++) {
for (int i = 0; i < v->live_intervals->num_vars; i++) {
if (BITSET_TEST(v->live_intervals->block_data[block].livein, i)) {
int vgrf = v->live_intervals->vgrf_from_var[i];
if (!BITSET_TEST(livein[block], vgrf)) {
reg_pressure_in[block] += v->alloc.sizes[vgrf];
BITSET_SET(livein[block], vgrf);
}
}
if (BITSET_TEST(v->live_intervals->block_data[block].liveout, i))
BITSET_SET(liveout[block], v->live_intervals->vgrf_from_var[i]);
}
}
/* Now, extend the live in/live out sets for when a range crosses a block
* boundary, which matches what our register allocator/interference code
* does to account for force_writemask_all and incompatible exec_mask's.
*/
for (int block = 0; block < cfg->num_blocks - 1; block++) {
for (int i = 0; i < grf_count; i++) {
if (v->virtual_grf_start[i] <= cfg->blocks[block]->end_ip &&
v->virtual_grf_end[i] >= cfg->blocks[block + 1]->start_ip) {
if (!BITSET_TEST(livein[block + 1], i)) {
reg_pressure_in[block + 1] += v->alloc.sizes[i];
BITSET_SET(livein[block + 1], i);
}
BITSET_SET(liveout[block], i);
}
}
}
int payload_last_use_ip[hw_reg_count];
v->calculate_payload_ranges(hw_reg_count, payload_last_use_ip);
for (int i = 0; i < hw_reg_count; i++) {
if (payload_last_use_ip[i] == -1)
continue;
for (int block = 0; block < cfg->num_blocks; block++) {
if (cfg->blocks[block]->start_ip <= payload_last_use_ip[i])
reg_pressure_in[block]++;
if (cfg->blocks[block]->end_ip <= payload_last_use_ip[i])
BITSET_SET(hw_liveout[block], i);
}
}
}
void
fs_instruction_scheduler::update_register_pressure(backend_instruction *be)
{
fs_inst *inst = (fs_inst *)be;
if (!reads_remaining)
return;
if (inst->dst.file == VGRF) {
written[inst->dst.nr] = true;
}
for (int i = 0; i < inst->sources; i++) {
if (is_src_duplicate(inst, i))
continue;
if (inst->src[i].file == VGRF) {
reads_remaining[inst->src[i].nr]--;
} else if (inst->src[i].file == FIXED_GRF &&
inst->src[i].nr < hw_reg_count) {
for (unsigned off = 0; off < regs_read(inst, i); off++)
hw_reads_remaining[inst->src[i].nr + off]--;
}
}
}
int
fs_instruction_scheduler::get_register_pressure_benefit(backend_instruction *be)
{
fs_inst *inst = (fs_inst *)be;
int benefit = 0;
if (inst->dst.file == VGRF) {
if (!BITSET_TEST(livein[block_idx], inst->dst.nr) &&
!written[inst->dst.nr])
benefit -= v->alloc.sizes[inst->dst.nr];
}
for (int i = 0; i < inst->sources; i++) {
if (is_src_duplicate(inst, i))
continue;
if (inst->src[i].file == VGRF &&
!BITSET_TEST(liveout[block_idx], inst->src[i].nr) &&
reads_remaining[inst->src[i].nr] == 1)
benefit += v->alloc.sizes[inst->src[i].nr];
if (inst->src[i].file == FIXED_GRF &&
inst->src[i].nr < hw_reg_count) {
for (unsigned off = 0; off < regs_read(inst, i); off++) {
int reg = inst->src[i].nr + off;
if (!BITSET_TEST(hw_liveout[block_idx], reg) &&
hw_reads_remaining[reg] == 1) {
benefit++;
}
}
}
}
return benefit;
}
class vec4_instruction_scheduler : public instruction_scheduler
{
public:
vec4_instruction_scheduler(vec4_visitor *v, int grf_count);
void calculate_deps();
schedule_node *choose_instruction_to_schedule();
int issue_time(backend_instruction *inst);
vec4_visitor *v;
void count_reads_remaining(backend_instruction *inst);
void setup_liveness(cfg_t *cfg);
void update_register_pressure(backend_instruction *inst);
int get_register_pressure_benefit(backend_instruction *inst);
};
vec4_instruction_scheduler::vec4_instruction_scheduler(vec4_visitor *v,
int grf_count)
: instruction_scheduler(v, grf_count, 0, 0, SCHEDULE_POST),
v(v)
{
}
void
vec4_instruction_scheduler::count_reads_remaining(backend_instruction *be)
{
}
void
vec4_instruction_scheduler::setup_liveness(cfg_t *cfg)
{
}
void
vec4_instruction_scheduler::update_register_pressure(backend_instruction *be)
{
}
int
vec4_instruction_scheduler::get_register_pressure_benefit(backend_instruction *be)
{
return 0;
}
schedule_node::schedule_node(backend_instruction *inst,
instruction_scheduler *sched)
{
const struct gen_device_info *devinfo = sched->bs->devinfo;
this->inst = inst;
this->child_array_size = 0;
this->children = NULL;
this->child_latency = NULL;
this->child_count = 0;
this->parent_count = 0;
this->unblocked_time = 0;
this->cand_generation = 0;
this->delay = 0;
this->exit = NULL;
/* We can't measure Gen6 timings directly but expect them to be much
* closer to Gen7 than Gen4.
*/
if (!sched->post_reg_alloc)
this->latency = 1;
else if (devinfo->gen >= 6)
set_latency_gen7(devinfo->is_haswell);
else
set_latency_gen4();
}
void
instruction_scheduler::add_insts_from_block(bblock_t *block)
{
foreach_inst_in_block(backend_instruction, inst, block) {
schedule_node *n = new(mem_ctx) schedule_node(inst, this);
instructions.push_tail(n);
}
this->instructions_to_schedule = block->end_ip - block->start_ip + 1;
}
/** Computation of the delay member of each node. */
void
instruction_scheduler::compute_delays()
{
foreach_in_list_reverse(schedule_node, n, &instructions) {
if (!n->child_count) {
n->delay = issue_time(n->inst);
} else {
for (int i = 0; i < n->child_count; i++) {
assert(n->children[i]->delay);
n->delay = MAX2(n->delay, n->latency + n->children[i]->delay);
}
}
}
}
void
instruction_scheduler::compute_exits()
{
/* Calculate a lower bound of the scheduling time of each node in the
* graph. This is analogous to the node's critical path but calculated
* from the top instead of from the bottom of the block.
*/
foreach_in_list(schedule_node, n, &instructions) {
for (int i = 0; i < n->child_count; i++) {
n->children[i]->unblocked_time =
MAX2(n->children[i]->unblocked_time,
n->unblocked_time + issue_time(n->inst) + n->child_latency[i]);
}
}
/* Calculate the exit of each node by induction based on the exit nodes of
* its children. The preferred exit of a node is the one among the exit
* nodes of its children which can be unblocked first according to the
* optimistic unblocked time estimate calculated above.
*/
foreach_in_list_reverse(schedule_node, n, &instructions) {
n->exit = (n->inst->opcode == FS_OPCODE_DISCARD_JUMP ? n : NULL);
for (int i = 0; i < n->child_count; i++) {
if (exit_unblocked_time(n->children[i]) < exit_unblocked_time(n))
n->exit = n->children[i]->exit;
}
}
}
/**
* Add a dependency between two instruction nodes.
*
* The @after node will be scheduled after @before. We will try to
* schedule it @latency cycles after @before, but no guarantees there.
*/
void
instruction_scheduler::add_dep(schedule_node *before, schedule_node *after,
int latency)
{
if (!before || !after)
return;
assert(before != after);
for (int i = 0; i < before->child_count; i++) {
if (before->children[i] == after) {
before->child_latency[i] = MAX2(before->child_latency[i], latency);
return;
}
}
if (before->child_array_size <= before->child_count) {
if (before->child_array_size < 16)
before->child_array_size = 16;
else
before->child_array_size *= 2;
before->children = reralloc(mem_ctx, before->children,
schedule_node *,
before->child_array_size);
before->child_latency = reralloc(mem_ctx, before->child_latency,
int, before->child_array_size);
}
before->children[before->child_count] = after;
before->child_latency[before->child_count] = latency;
before->child_count++;
after->parent_count++;
}
void
instruction_scheduler::add_dep(schedule_node *before, schedule_node *after)
{
if (!before)
return;
add_dep(before, after, before->latency);
}
static bool
is_scheduling_barrier(const backend_instruction *inst)
{
return inst->opcode == FS_OPCODE_PLACEHOLDER_HALT ||
inst->is_control_flow() ||
inst->has_side_effects();
}
/**
* Sometimes we really want this node to execute after everything that
* was before it and before everything that followed it. This adds
* the deps to do so.
*/
void
instruction_scheduler::add_barrier_deps(schedule_node *n)
{
schedule_node *prev = (schedule_node *)n->prev;
schedule_node *next = (schedule_node *)n->next;
if (prev) {
while (!prev->is_head_sentinel()) {
add_dep(prev, n, 0);
if (is_scheduling_barrier(prev->inst))
break;
prev = (schedule_node *)prev->prev;
}
}
if (next) {
while (!next->is_tail_sentinel()) {
add_dep(n, next, 0);
if (is_scheduling_barrier(next->inst))
break;
next = (schedule_node *)next->next;
}
}
}
/* instruction scheduling needs to be aware of when an MRF write
* actually writes 2 MRFs.
*/
bool
fs_instruction_scheduler::is_compressed(fs_inst *inst)
{
return inst->exec_size == 16;
}
void
fs_instruction_scheduler::calculate_deps()
{
/* Pre-register-allocation, this tracks the last write per VGRF offset.
* After register allocation, reg_offsets are gone and we track individual
* GRF registers.
*/
schedule_node *last_grf_write[grf_count * 16];
schedule_node *last_mrf_write[BRW_MAX_MRF(v->devinfo->gen)];
schedule_node *last_conditional_mod[4] = {};
schedule_node *last_accumulator_write = NULL;
/* Fixed HW registers are assumed to be separate from the virtual
* GRFs, so they can be tracked separately. We don't really write
* to fixed GRFs much, so don't bother tracking them on a more
* granular level.
*/
schedule_node *last_fixed_grf_write = NULL;
memset(last_grf_write, 0, sizeof(last_grf_write));
memset(last_mrf_write, 0, sizeof(last_mrf_write));
/* top-to-bottom dependencies: RAW and WAW. */
foreach_in_list(schedule_node, n, &instructions) {
fs_inst *inst = (fs_inst *)n->inst;
if (is_scheduling_barrier(inst))
add_barrier_deps(n);
/* read-after-write deps. */
for (int i = 0; i < inst->sources; i++) {
if (inst->src[i].file == VGRF) {
if (post_reg_alloc) {
for (unsigned r = 0; r < regs_read(inst, i); r++)
add_dep(last_grf_write[inst->src[i].nr + r], n);
} else {
for (unsigned r = 0; r < regs_read(inst, i); r++) {
add_dep(last_grf_write[inst->src[i].nr * 16 +
inst->src[i].offset / REG_SIZE + r], n);
}
}
} else if (inst->src[i].file == FIXED_GRF) {
if (post_reg_alloc) {
for (unsigned r = 0; r < regs_read(inst, i); r++)
add_dep(last_grf_write[inst->src[i].nr + r], n);
} else {
add_dep(last_fixed_grf_write, n);
}
} else if (inst->src[i].is_accumulator()) {
add_dep(last_accumulator_write, n);
} else if (inst->src[i].file == ARF) {
add_barrier_deps(n);
}
}
if (inst->base_mrf != -1) {
for (int i = 0; i < inst->mlen; i++) {
/* It looks like the MRF regs are released in the send
* instruction once it's sent, not when the result comes
* back.
*/
add_dep(last_mrf_write[inst->base_mrf + i], n);
}
}
if (const unsigned mask = inst->flags_read(v->devinfo)) {
assert(mask < (1 << ARRAY_SIZE(last_conditional_mod)));
for (unsigned i = 0; i < ARRAY_SIZE(last_conditional_mod); i++) {
if (mask & (1 << i))
add_dep(last_conditional_mod[i], n);
}
}
if (inst->reads_accumulator_implicitly()) {
add_dep(last_accumulator_write, n);
}
/* write-after-write deps. */
if (inst->dst.file == VGRF) {
if (post_reg_alloc) {
for (unsigned r = 0; r < regs_written(inst); r++) {
add_dep(last_grf_write[inst->dst.nr + r], n);
last_grf_write[inst->dst.nr + r] = n;
}
} else {
for (unsigned r = 0; r < regs_written(inst); r++) {
add_dep(last_grf_write[inst->dst.nr * 16 +
inst->dst.offset / REG_SIZE + r], n);
last_grf_write[inst->dst.nr * 16 +
inst->dst.offset / REG_SIZE + r] = n;
}
}
} else if (inst->dst.file == MRF) {
int reg = inst->dst.nr & ~BRW_MRF_COMPR4;
add_dep(last_mrf_write[reg], n);
last_mrf_write[reg] = n;
if (is_compressed(inst)) {
if (inst->dst.nr & BRW_MRF_COMPR4)
reg += 4;
else
reg++;
add_dep(last_mrf_write[reg], n);
last_mrf_write[reg] = n;
}
} else if (inst->dst.file == FIXED_GRF) {
if (post_reg_alloc) {
for (unsigned r = 0; r < regs_written(inst); r++)
last_grf_write[inst->dst.nr + r] = n;
} else {
last_fixed_grf_write = n;
}
} else if (inst->dst.is_accumulator()) {
add_dep(last_accumulator_write, n);
last_accumulator_write = n;
} else if (inst->dst.file == ARF && !inst->dst.is_null()) {
add_barrier_deps(n);
}
if (inst->mlen > 0 && inst->base_mrf != -1) {
for (int i = 0; i < v->implied_mrf_writes(inst); i++) {
add_dep(last_mrf_write[inst->base_mrf + i], n);
last_mrf_write[inst->base_mrf + i] = n;
}
}
if (const unsigned mask = inst->flags_written()) {
assert(mask < (1 << ARRAY_SIZE(last_conditional_mod)));
for (unsigned i = 0; i < ARRAY_SIZE(last_conditional_mod); i++) {
if (mask & (1 << i)) {
add_dep(last_conditional_mod[i], n, 0);
last_conditional_mod[i] = n;
}
}
}
if (inst->writes_accumulator_implicitly(v->devinfo) &&
!inst->dst.is_accumulator()) {
add_dep(last_accumulator_write, n);
last_accumulator_write = n;
}
}
/* bottom-to-top dependencies: WAR */
memset(last_grf_write, 0, sizeof(last_grf_write));
memset(last_mrf_write, 0, sizeof(last_mrf_write));
memset(last_conditional_mod, 0, sizeof(last_conditional_mod));
last_accumulator_write = NULL;
last_fixed_grf_write = NULL;
foreach_in_list_reverse_safe(schedule_node, n, &instructions) {
fs_inst *inst = (fs_inst *)n->inst;
/* write-after-read deps. */
for (int i = 0; i < inst->sources; i++) {
if (inst->src[i].file == VGRF) {
if (post_reg_alloc) {
for (unsigned r = 0; r < regs_read(inst, i); r++)
add_dep(n, last_grf_write[inst->src[i].nr + r], 0);
} else {
for (unsigned r = 0; r < regs_read(inst, i); r++) {
add_dep(n, last_grf_write[inst->src[i].nr * 16 +
inst->src[i].offset / REG_SIZE + r], 0);
}
}
} else if (inst->src[i].file == FIXED_GRF) {
if (post_reg_alloc) {
for (unsigned r = 0; r < regs_read(inst, i); r++)
add_dep(n, last_grf_write[inst->src[i].nr + r], 0);
} else {
add_dep(n, last_fixed_grf_write, 0);
}
} else if (inst->src[i].is_accumulator()) {
add_dep(n, last_accumulator_write, 0);
} else if (inst->src[i].file == ARF) {
add_barrier_deps(n);
}
}
if (inst->base_mrf != -1) {
for (int i = 0; i < inst->mlen; i++) {
/* It looks like the MRF regs are released in the send
* instruction once it's sent, not when the result comes
* back.
*/
add_dep(n, last_mrf_write[inst->base_mrf + i], 2);
}
}
if (const unsigned mask = inst->flags_read(v->devinfo)) {
assert(mask < (1 << ARRAY_SIZE(last_conditional_mod)));
for (unsigned i = 0; i < ARRAY_SIZE(last_conditional_mod); i++) {
if (mask & (1 << i))
add_dep(n, last_conditional_mod[i]);
}
}
if (inst->reads_accumulator_implicitly()) {
add_dep(n, last_accumulator_write);
}
/* Update the things this instruction wrote, so earlier reads
* can mark this as WAR dependency.
*/
if (inst->dst.file == VGRF) {
if (post_reg_alloc) {
for (unsigned r = 0; r < regs_written(inst); r++)
last_grf_write[inst->dst.nr + r] = n;
} else {
for (unsigned r = 0; r < regs_written(inst); r++) {
last_grf_write[inst->dst.nr * 16 +
inst->dst.offset / REG_SIZE + r] = n;
}
}
} else if (inst->dst.file == MRF) {
int reg = inst->dst.nr & ~BRW_MRF_COMPR4;
last_mrf_write[reg] = n;
if (is_compressed(inst)) {
if (inst->dst.nr & BRW_MRF_COMPR4)
reg += 4;
else
reg++;
last_mrf_write[reg] = n;
}
} else if (inst->dst.file == FIXED_GRF) {
if (post_reg_alloc) {
for (unsigned r = 0; r < regs_written(inst); r++)
last_grf_write[inst->dst.nr + r] = n;
} else {
last_fixed_grf_write = n;
}
} else if (inst->dst.is_accumulator()) {
last_accumulator_write = n;
} else if (inst->dst.file == ARF && !inst->dst.is_null()) {
add_barrier_deps(n);
}
if (inst->mlen > 0 && inst->base_mrf != -1) {
for (int i = 0; i < v->implied_mrf_writes(inst); i++) {
last_mrf_write[inst->base_mrf + i] = n;
}
}
if (const unsigned mask = inst->flags_written()) {
assert(mask < (1 << ARRAY_SIZE(last_conditional_mod)));
for (unsigned i = 0; i < ARRAY_SIZE(last_conditional_mod); i++) {
if (mask & (1 << i))
last_conditional_mod[i] = n;
}
}
if (inst->writes_accumulator_implicitly(v->devinfo)) {
last_accumulator_write = n;
}
}
}
void
vec4_instruction_scheduler::calculate_deps()
{
schedule_node *last_grf_write[grf_count];
schedule_node *last_mrf_write[BRW_MAX_MRF(v->devinfo->gen)];
schedule_node *last_conditional_mod = NULL;
schedule_node *last_accumulator_write = NULL;
/* Fixed HW registers are assumed to be separate from the virtual
* GRFs, so they can be tracked separately. We don't really write
* to fixed GRFs much, so don't bother tracking them on a more
* granular level.
*/
schedule_node *last_fixed_grf_write = NULL;
memset(last_grf_write, 0, sizeof(last_grf_write));
memset(last_mrf_write, 0, sizeof(last_mrf_write));
/* top-to-bottom dependencies: RAW and WAW. */
foreach_in_list(schedule_node, n, &instructions) {
vec4_instruction *inst = (vec4_instruction *)n->inst;
if (is_scheduling_barrier(inst))
add_barrier_deps(n);
/* read-after-write deps. */
for (int i = 0; i < 3; i++) {
if (inst->src[i].file == VGRF) {
for (unsigned j = 0; j < regs_read(inst, i); ++j)
add_dep(last_grf_write[inst->src[i].nr + j], n);
} else if (inst->src[i].file == FIXED_GRF) {
add_dep(last_fixed_grf_write, n);
} else if (inst->src[i].is_accumulator()) {
assert(last_accumulator_write);
add_dep(last_accumulator_write, n);
} else if (inst->src[i].file == ARF) {
add_barrier_deps(n);
}
}
if (!inst->is_send_from_grf()) {
for (int i = 0; i < inst->mlen; i++) {
/* It looks like the MRF regs are released in the send
* instruction once it's sent, not when the result comes
* back.
*/
add_dep(last_mrf_write[inst->base_mrf + i], n);
}
}
if (inst->reads_flag()) {
assert(last_conditional_mod);
add_dep(last_conditional_mod, n);
}
if (inst->reads_accumulator_implicitly()) {
assert(last_accumulator_write);
add_dep(last_accumulator_write, n);
}
/* write-after-write deps. */
if (inst->dst.file == VGRF) {
for (unsigned j = 0; j < regs_written(inst); ++j) {
add_dep(last_grf_write[inst->dst.nr + j], n);
last_grf_write[inst->dst.nr + j] = n;
}
} else if (inst->dst.file == MRF) {
add_dep(last_mrf_write[inst->dst.nr], n);
last_mrf_write[inst->dst.nr] = n;
} else if (inst->dst.file == FIXED_GRF) {
last_fixed_grf_write = n;
} else if (inst->dst.is_accumulator()) {
add_dep(last_accumulator_write, n);
last_accumulator_write = n;
} else if (inst->dst.file == ARF && !inst->dst.is_null()) {
add_barrier_deps(n);
}
if (inst->mlen > 0 && !inst->is_send_from_grf()) {
for (int i = 0; i < v->implied_mrf_writes(inst); i++) {
add_dep(last_mrf_write[inst->base_mrf + i], n);
last_mrf_write[inst->base_mrf + i] = n;
}
}
if (inst->writes_flag()) {
add_dep(last_conditional_mod, n, 0);
last_conditional_mod = n;
}
if (inst->writes_accumulator_implicitly(v->devinfo) &&
!inst->dst.is_accumulator()) {
add_dep(last_accumulator_write, n);
last_accumulator_write = n;
}
}
/* bottom-to-top dependencies: WAR */
memset(last_grf_write, 0, sizeof(last_grf_write));
memset(last_mrf_write, 0, sizeof(last_mrf_write));
last_conditional_mod = NULL;
last_accumulator_write = NULL;
last_fixed_grf_write = NULL;
foreach_in_list_reverse_safe(schedule_node, n, &instructions) {
vec4_instruction *inst = (vec4_instruction *)n->inst;
/* write-after-read deps. */
for (int i = 0; i < 3; i++) {
if (inst->src[i].file == VGRF) {
for (unsigned j = 0; j < regs_read(inst, i); ++j)
add_dep(n, last_grf_write[inst->src[i].nr + j]);
} else if (inst->src[i].file == FIXED_GRF) {
add_dep(n, last_fixed_grf_write);
} else if (inst->src[i].is_accumulator()) {
add_dep(n, last_accumulator_write);
} else if (inst->src[i].file == ARF) {
add_barrier_deps(n);
}
}
if (!inst->is_send_from_grf()) {
for (int i = 0; i < inst->mlen; i++) {
/* It looks like the MRF regs are released in the send
* instruction once it's sent, not when the result comes
* back.
*/
add_dep(n, last_mrf_write[inst->base_mrf + i], 2);
}
}
if (inst->reads_flag()) {
add_dep(n, last_conditional_mod);
}
if (inst->reads_accumulator_implicitly()) {
add_dep(n, last_accumulator_write);
}
/* Update the things this instruction wrote, so earlier reads
* can mark this as WAR dependency.
*/
if (inst->dst.file == VGRF) {
for (unsigned j = 0; j < regs_written(inst); ++j)
last_grf_write[inst->dst.nr + j] = n;
} else if (inst->dst.file == MRF) {
last_mrf_write[inst->dst.nr] = n;
} else if (inst->dst.file == FIXED_GRF) {
last_fixed_grf_write = n;
} else if (inst->dst.is_accumulator()) {
last_accumulator_write = n;
} else if (inst->dst.file == ARF && !inst->dst.is_null()) {
add_barrier_deps(n);
}
if (inst->mlen > 0 && !inst->is_send_from_grf()) {
for (int i = 0; i < v->implied_mrf_writes(inst); i++) {
last_mrf_write[inst->base_mrf + i] = n;
}
}
if (inst->writes_flag()) {
last_conditional_mod = n;
}
if (inst->writes_accumulator_implicitly(v->devinfo)) {
last_accumulator_write = n;
}
}
}
schedule_node *
fs_instruction_scheduler::choose_instruction_to_schedule()
{
schedule_node *chosen = NULL;
if (mode == SCHEDULE_PRE || mode == SCHEDULE_POST) {
int chosen_time = 0;
/* Of the instructions ready to execute or the closest to being ready,
* choose the one most likely to unblock an early program exit, or
* otherwise the oldest one.
*/
foreach_in_list(schedule_node, n, &instructions) {
if (!chosen ||
exit_unblocked_time(n) < exit_unblocked_time(chosen) ||
(exit_unblocked_time(n) == exit_unblocked_time(chosen) &&
n->unblocked_time < chosen_time)) {
chosen = n;
chosen_time = n->unblocked_time;
}
}
} else {
/* Before register allocation, we don't care about the latencies of
* instructions. All we care about is reducing live intervals of
* variables so that we can avoid register spilling, or get SIMD16
* shaders which naturally do a better job of hiding instruction
* latency.
*/
foreach_in_list(schedule_node, n, &instructions) {
fs_inst *inst = (fs_inst *)n->inst;
if (!chosen) {
chosen = n;
continue;
}
/* Most important: If we can definitely reduce register pressure, do
* so immediately.
*/
int register_pressure_benefit = get_register_pressure_benefit(n->inst);
int chosen_register_pressure_benefit =
get_register_pressure_benefit(chosen->inst);
if (register_pressure_benefit > 0 &&
register_pressure_benefit > chosen_register_pressure_benefit) {
chosen = n;
continue;
} else if (chosen_register_pressure_benefit > 0 &&
(register_pressure_benefit <
chosen_register_pressure_benefit)) {
continue;
}
if (mode == SCHEDULE_PRE_LIFO) {
/* Prefer instructions that recently became available for
* scheduling. These are the things that are most likely to
* (eventually) make a variable dead and reduce register pressure.
* Typical register pressure estimates don't work for us because
* most of our pressure comes from texturing, where no single
* instruction to schedule will make a vec4 value dead.
*/
if (n->cand_generation > chosen->cand_generation) {
chosen = n;
continue;
} else if (n->cand_generation < chosen->cand_generation) {
continue;
}
/* On MRF-using chips, prefer non-SEND instructions. If we don't
* do this, then because we prefer instructions that just became
* candidates, we'll end up in a pattern of scheduling a SEND,
* then the MRFs for the next SEND, then the next SEND, then the
* MRFs, etc., without ever consuming the results of a send.
*/
if (v->devinfo->gen < 7) {
fs_inst *chosen_inst = (fs_inst *)chosen->inst;
/* We use size_written > 4 * exec_size as our test for the kind
* of send instruction to avoid -- only sends generate many
* regs, and a single-result send is probably actually reducing
* register pressure.
*/
if (inst->size_written <= 4 * inst->exec_size &&
chosen_inst->size_written > 4 * chosen_inst->exec_size) {
chosen = n;
continue;
} else if (inst->size_written > chosen_inst->size_written) {
continue;
}
}
}
/* For instructions pushed on the cands list at the same time, prefer
* the one with the highest delay to the end of the program. This is
* most likely to have its values able to be consumed first (such as
* for a large tree of lowered ubo loads, which appear reversed in
* the instruction stream with respect to when they can be consumed).
*/
if (n->delay > chosen->delay) {
chosen = n;
continue;
} else if (n->delay < chosen->delay) {
continue;
}
/* Prefer the node most likely to unblock an early program exit.
*/
if (exit_unblocked_time(n) < exit_unblocked_time(chosen)) {
chosen = n;
continue;
} else if (exit_unblocked_time(n) > exit_unblocked_time(chosen)) {
continue;
}
/* If all other metrics are equal, we prefer the first instruction in
* the list (program execution).
*/
}
}
return chosen;
}
schedule_node *
vec4_instruction_scheduler::choose_instruction_to_schedule()
{
schedule_node *chosen = NULL;
int chosen_time = 0;
/* Of the instructions ready to execute or the closest to being ready,
* choose the oldest one.
*/
foreach_in_list(schedule_node, n, &instructions) {
if (!chosen || n->unblocked_time < chosen_time) {
chosen = n;
chosen_time = n->unblocked_time;
}
}
return chosen;
}
int
fs_instruction_scheduler::issue_time(backend_instruction *inst)
{
if (is_compressed((fs_inst *)inst))
return 4;
else
return 2;
}
int
vec4_instruction_scheduler::issue_time(backend_instruction *inst)
{
/* We always execute as two vec4s in parallel. */
return 2;
}
void
instruction_scheduler::schedule_instructions(bblock_t *block)
{
const struct gen_device_info *devinfo = bs->devinfo;
int time = 0;
if (!post_reg_alloc)
reg_pressure = reg_pressure_in[block->num];
block_idx = block->num;
/* Remove non-DAG heads from the list. */
foreach_in_list_safe(schedule_node, n, &instructions) {
if (n->parent_count != 0)
n->remove();
}
unsigned cand_generation = 1;
while (!instructions.is_empty()) {
schedule_node *chosen = choose_instruction_to_schedule();
/* Schedule this instruction. */
assert(chosen);
chosen->remove();
chosen->inst->exec_node::remove();
block->instructions.push_tail(chosen->inst);
instructions_to_schedule--;
if (!post_reg_alloc) {
reg_pressure -= get_register_pressure_benefit(chosen->inst);
update_register_pressure(chosen->inst);
}
/* If we expected a delay for scheduling, then bump the clock to reflect
* that. In reality, the hardware will switch to another hyperthread
* and may not return to dispatching our thread for a while even after
* we're unblocked. After this, we have the time when the chosen
* instruction will start executing.
*/
time = MAX2(time, chosen->unblocked_time);
/* Update the clock for how soon an instruction could start after the
* chosen one.
*/
time += issue_time(chosen->inst);
if (debug) {
fprintf(stderr, "clock %4d, scheduled: ", time);
bs->dump_instruction(chosen->inst);
if (!post_reg_alloc)
fprintf(stderr, "(register pressure %d)\n", reg_pressure);
}
/* Now that we've scheduled a new instruction, some of its
* children can be promoted to the list of instructions ready to
* be scheduled. Update the children's unblocked time for this
* DAG edge as we do so.
*/
for (int i = chosen->child_count - 1; i >= 0; i--) {
schedule_node *child = chosen->children[i];
child->unblocked_time = MAX2(child->unblocked_time,
time + chosen->child_latency[i]);
if (debug) {
fprintf(stderr, "\tchild %d, %d parents: ", i, child->parent_count);
bs->dump_instruction(child->inst);
}
child->cand_generation = cand_generation;
child->parent_count--;
if (child->parent_count == 0) {
if (debug) {
fprintf(stderr, "\t\tnow available\n");
}
instructions.push_head(child);
}
}
cand_generation++;
/* Shared resource: the mathbox. There's one mathbox per EU on Gen6+
* but it's more limited pre-gen6, so if we send something off to it then
* the next math instruction isn't going to make progress until the first
* is done.
*/
if (devinfo->gen < 6 && chosen->inst->is_math()) {
foreach_in_list(schedule_node, n, &instructions) {
if (n->inst->is_math())
n->unblocked_time = MAX2(n->unblocked_time,
time + chosen->latency);
}
}
}
assert(instructions_to_schedule == 0);
block->cycle_count = time;
}
static unsigned get_cycle_count(cfg_t *cfg)
{
unsigned count = 0, multiplier = 1;
foreach_block(block, cfg) {
if (block->start()->opcode == BRW_OPCODE_DO)
multiplier *= 10; /* assume that loops execute ~10 times */
count += block->cycle_count * multiplier;
if (block->end()->opcode == BRW_OPCODE_WHILE)
multiplier /= 10;
}
return count;
}
void
instruction_scheduler::run(cfg_t *cfg)
{
if (debug && !post_reg_alloc) {
fprintf(stderr, "\nInstructions before scheduling (reg_alloc %d)\n",
post_reg_alloc);
bs->dump_instructions();
}
if (!post_reg_alloc)
setup_liveness(cfg);
foreach_block(block, cfg) {
if (reads_remaining) {
memset(reads_remaining, 0,
grf_count * sizeof(*reads_remaining));
memset(hw_reads_remaining, 0,
hw_reg_count * sizeof(*hw_reads_remaining));
memset(written, 0, grf_count * sizeof(*written));
foreach_inst_in_block(fs_inst, inst, block)
count_reads_remaining(inst);
}
add_insts_from_block(block);
calculate_deps();
compute_delays();
compute_exits();
schedule_instructions(block);
}
if (debug && !post_reg_alloc) {
fprintf(stderr, "\nInstructions after scheduling (reg_alloc %d)\n",
post_reg_alloc);
bs->dump_instructions();
}
cfg->cycle_count = get_cycle_count(cfg);
}
void
fs_visitor::schedule_instructions(instruction_scheduler_mode mode)
{
if (mode != SCHEDULE_POST)
calculate_live_intervals();
int grf_count;
if (mode == SCHEDULE_POST)
grf_count = grf_used;
else
grf_count = alloc.count;
fs_instruction_scheduler sched(this, grf_count, first_non_payload_grf,
cfg->num_blocks, mode);
sched.run(cfg);
invalidate_live_intervals();
}
void
vec4_visitor::opt_schedule_instructions()
{
vec4_instruction_scheduler sched(this, prog_data->total_grf);
sched.run(cfg);
invalidate_live_intervals();
}