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v3d: add shader-db stat to count SFU stalls 

SFU operations have a latency of 2 cicles, so if their results
are used in the following cycle to a SFU instruction, the GPU
stalls for an extra cycle until the result is available.

This adds the number of stalls to the shader-db debug mode and
sum of instruction + stalls to evaluate optimizations to schedule
instructions that avoid generating sfu-stalls.

v2: Rename v3d_qpu_generates_sfu_stalls to v3d_qpu_instr_is_sfu (Eric)

Reviewed-by: Eric Anholt <eric@anholt.net>
This commit is contained in:
Jose Maria Casanova Crespo 2019-07-02 18:31:09 +02:00
parent f7224014df
commit c341ab7ffb
5 changed files with 74 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

45
src/broadcom/compiler/qpu_schedule.c
View File

@ -440,6 +440,8 @@ struct choose_scoreboard {
struct dag *dag;
int tick;
int last_magic_sfu_write_tick;
int last_stallable_sfu_reg;
int last_stallable_sfu_tick;
int last_ldvary_tick;
int last_uniforms_reset_tick;
int last_thrsw_tick;
@ -531,6 +533,33 @@ pixel_scoreboard_too_soon(struct choose_scoreboard *scoreboard,
return (scoreboard->tick == 0 && qpu_inst_is_tlb(inst));
}
static bool
qpu_instruction_uses_rf(const struct v3d_qpu_instr *inst,
uint32_t waddr) {
if (inst->type != V3D_QPU_INSTR_TYPE_ALU)
return false;
if (v3d_qpu_uses_mux(inst, V3D_QPU_MUX_A) &&
inst->raddr_a == waddr)
return true;
if (v3d_qpu_uses_mux(inst, V3D_QPU_MUX_B) &&
!inst->sig.small_imm && (inst->raddr_b == waddr))
return true;
return false;
}
static bool
mux_read_stalls(struct choose_scoreboard *scoreboard,
const struct v3d_qpu_instr *inst)
{
return scoreboard->tick == scoreboard->last_stallable_sfu_tick + 1 &&
qpu_instruction_uses_rf(inst,
scoreboard->last_stallable_sfu_reg);
}
static int
get_instruction_priority(const struct v3d_qpu_instr *inst)
{
@ -851,6 +880,16 @@ update_scoreboard_for_magic_waddr(struct choose_scoreboard *scoreboard,
scoreboard->last_magic_sfu_write_tick = scoreboard->tick;
}
static void
update_scoreboard_for_sfu_stall_waddr(struct choose_scoreboard *scoreboard,
const struct v3d_qpu_instr *inst)
{
if (v3d_qpu_instr_is_sfu(inst)) {
scoreboard->last_stallable_sfu_reg = inst->alu.add.waddr;
scoreboard->last_stallable_sfu_tick = scoreboard->tick;
}
}
static void
update_scoreboard_for_chosen(struct choose_scoreboard *scoreboard,
const struct v3d_qpu_instr *inst)
@ -864,6 +903,9 @@ update_scoreboard_for_chosen(struct choose_scoreboard *scoreboard,
if (inst->alu.add.magic_write) {
update_scoreboard_for_magic_waddr(scoreboard,
inst->alu.add.waddr);
} else {
update_scoreboard_for_sfu_stall_waddr(scoreboard,
inst);
}
}
@ -1298,6 +1340,8 @@ schedule_instructions(struct v3d_compile *c,
fprintf(stderr, "\n");
}
}
if (mux_read_stalls(scoreboard, inst))
c->qpu_inst_stalled_count++;
}
/* Update the uniform index for the rewritten location --
@ -1481,6 +1525,7 @@ v3d_qpu_schedule_instructions(struct v3d_compile *c)
scoreboard.last_magic_sfu_write_tick = -10;
scoreboard.last_uniforms_reset_tick = -10;
scoreboard.last_thrsw_tick = -10;
scoreboard.last_stallable_sfu_tick = -10;
if (debug) {
fprintf(stderr, "Pre-schedule instructions\n");

1
src/broadcom/compiler/v3d_compiler.h
View File

@ -613,6 +613,7 @@ struct v3d_compile {
uint64_t *qpu_insts;
uint32_t qpu_inst_count;
uint32_t qpu_inst_size;
uint32_t qpu_inst_stalled_count;
/* For the FS, the number of varying inputs not counting the
* point/line varyings payload

7
src/broadcom/compiler/vir.c
View File

@ -947,7 +947,8 @@ uint64_t *v3d_compile(const struct v3d_compiler *compiler,
char *shaderdb;
int ret = asprintf(&shaderdb,
"%s shader: %d inst, %d threads, %d loops, "
"%d uniforms, %d max-temps, %d:%d spills:fills",
"%d uniforms, %d max-temps, %d:%d spills:fills, "
"%d sfu-stalls, %d inst-and-stalls",
vir_get_stage_name(c),
c->qpu_inst_count,
c->threads,
@ -955,7 +956,9 @@ uint64_t *v3d_compile(const struct v3d_compiler *compiler,
c->num_uniforms,
vir_get_max_temps(c),
c->spills,
c->fills);
c->fills,
c->qpu_inst_stalled_count,
c->qpu_inst_count + c->qpu_inst_stalled_count);
if (ret >= 0) {
if (V3D_DEBUG & V3D_DEBUG_SHADERDB)
fprintf(stderr, "SHADER-DB: %s\n", shaderdb);

34
src/broadcom/qpu/qpu_instr.c
View File

@ -645,19 +645,10 @@ v3d_qpu_uses_tlb(const struct v3d_qpu_instr *inst)
bool
v3d_qpu_uses_sfu(const struct v3d_qpu_instr *inst)
{
if (inst->type == V3D_QPU_INSTR_TYPE_ALU) {
switch (inst->alu.add.op) {
case V3D_QPU_A_RECIP:
case V3D_QPU_A_RSQRT:
case V3D_QPU_A_EXP:
case V3D_QPU_A_LOG:
case V3D_QPU_A_SIN:
case V3D_QPU_A_RSQRT2:
return true;
default:
break;
}
if (v3d_qpu_instr_is_sfu(inst))
return true;
if (inst->type == V3D_QPU_INSTR_TYPE_ALU) {
if (inst->alu.add.magic_write &&
v3d_qpu_magic_waddr_is_sfu(inst->alu.add.waddr)) {
return true;
@ -672,6 +663,25 @@ v3d_qpu_uses_sfu(const struct v3d_qpu_instr *inst)
return false;
}
bool
v3d_qpu_instr_is_sfu(const struct v3d_qpu_instr *inst)
{
if (inst->type == V3D_QPU_INSTR_TYPE_ALU) {
switch (inst->alu.add.op) {
case V3D_QPU_A_RECIP:
case V3D_QPU_A_RSQRT:
case V3D_QPU_A_EXP:
case V3D_QPU_A_LOG:
case V3D_QPU_A_SIN:
case V3D_QPU_A_RSQRT2:
return true;
default:
return false;
}
}
return false;
}
bool
v3d_qpu_writes_tmu(const struct v3d_qpu_instr *inst)
{

1
src/broadcom/qpu/qpu_instr.h
View File

@ -447,6 +447,7 @@ bool v3d_qpu_magic_waddr_is_vpm(enum v3d_qpu_waddr waddr) ATTRIBUTE_CONST;
bool v3d_qpu_magic_waddr_is_tsy(enum v3d_qpu_waddr waddr) ATTRIBUTE_CONST;
bool v3d_qpu_magic_waddr_loads_unif(enum v3d_qpu_waddr waddr) ATTRIBUTE_CONST;
bool v3d_qpu_uses_tlb(const struct v3d_qpu_instr *inst) ATTRIBUTE_CONST;
bool v3d_qpu_instr_is_sfu(const struct v3d_qpu_instr *inst) ATTRIBUTE_CONST;
bool v3d_qpu_uses_sfu(const struct v3d_qpu_instr *inst) ATTRIBUTE_CONST;
bool v3d_qpu_writes_tmu(const struct v3d_qpu_instr *inst) ATTRIBUTE_CONST;
bool v3d_qpu_writes_tmu_not_tmuc(const struct v3d_qpu_instr *inst) ATTRIBUTE_CONST;