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v3d: Rematerialize MOVs of uniforms instead of spilling them. 

If we have a MOV of a uniform value available to spill, that's one of our
best choices.  We can just not spill the value, and emit a new load of the
uniform as the fill.  This saves bothering the TMU and the thrsw, and is
the same cost in uniforms (since the spill offset is a uniform anyway).

This doesn't have a huge impact on shader-db, since there aren't a whole
lot of spills and we usually copy-prop the uniforms at the VIR level such
that the only uniform MOVs are from vir_lower_uniforms:

total instructions in shared programs: 6430292 -> 6430279 (<.01%)
total uniforms in shared programs: 2386023 -> 2385787 (<.01%)
total spills in shared programs: 4961 -> 4960 (-0.02%)
total fills in shared programs: 6352 -> 6350 (-0.03%)

However, I'm interested in dropping the uniforms copy-prop in the backend,
since it would be cheaper to not load repeated uniforms if we have the
registers to spare.  This also saves many spills on
dEQP-GLES31.functional.ubo.random.all_per_block_buffers.20, which is what
motivated a bunch of my recent backend work in the first place:

before: 46 spills, 106 fills, 3062 instructions
after: 0 spills, 0 fills, 2611 instructions
This commit is contained in:
Eric Anholt 2019-02-25 15:36:26 -08:00
parent e0fada983d
commit 97566efe5c
2 changed files with 67 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
src/broadcom/compiler/v3d_compiler.h
View File

@ -1152,4 +1152,8 @@ vir_BRANCH(struct v3d_compile *c, enum v3d_qpu_branch_cond cond)
vir_for_each_block(_block, c) \
vir_for_each_inst(inst, _block)
#define vir_for_each_inst_inorder_safe(inst, c) \
vir_for_each_block(_block, c) \
vir_for_each_inst_safe(inst, _block)
#endif /* V3D_COMPILER_H */

89
src/broadcom/compiler/vir_register_allocate.c
View File

@ -47,10 +47,21 @@ is_last_ldtmu(struct qinst *inst, struct qblock *block)
return true;
}
static bool
vir_is_mov_uniform(struct v3d_compile *c, int temp)
{
struct qinst *def = c->defs[temp];
return (def &&
vir_is_raw_mov(def) &&
def->src[0].file == QFILE_UNIF);
}
static int
v3d_choose_spill_node(struct v3d_compile *c, struct ra_graph *g,
uint32_t *temp_to_node)
{
const float tmu_scale = 5;
float block_scale = 1.0;
float spill_costs[c->num_temps];
bool in_tmu_operation = false;
@ -75,22 +86,28 @@ v3d_choose_spill_node(struct v3d_compile *c, struct ra_graph *g,
continue;
int temp = inst->src[i].index;
if (no_spilling) {
BITSET_CLEAR(c->spillable,
temp);
} else {
if (vir_is_mov_uniform(c, temp)) {
spill_costs[temp] += block_scale;
} else if (!no_spilling) {
spill_costs[temp] += (block_scale *
tmu_scale);
} else {
BITSET_CLEAR(c->spillable, temp);
}
}
if (inst->dst.file == QFILE_TEMP) {
int temp = inst->dst.index;
if (no_spilling) {
BITSET_CLEAR(c->spillable,
temp);
if (vir_is_mov_uniform(c, temp)) {
/* We just rematerialize the unform
* later.
*/
} else if (!no_spilling) {
spill_costs[temp] += (block_scale *
tmu_scale);
} else {
spill_costs[temp] += block_scale;
BITSET_CLEAR(c->spillable, temp);
}
}
@ -184,18 +201,28 @@ v3d_emit_spill_tmua(struct v3d_compile *c, uint32_t spill_offset)
static void
v3d_spill_reg(struct v3d_compile *c, int spill_temp)
{
uint32_t spill_offset = c->spill_size;
c->spill_size += 16 * sizeof(uint32_t);
bool is_uniform = vir_is_mov_uniform(c, spill_temp);
if (spill_offset == 0)
v3d_setup_spill_base(c);
uint32_t spill_offset = 0;
if (!is_uniform) {
uint32_t spill_offset = c->spill_size;
c->spill_size += 16 * sizeof(uint32_t);
if (spill_offset == 0)
v3d_setup_spill_base(c);
}
struct qinst *last_thrsw = c->last_thrsw;
assert(!last_thrsw || last_thrsw->is_last_thrsw);
int start_num_temps = c->num_temps;
vir_for_each_inst_inorder(inst, c) {
struct qreg uniform_src = c->undef;
if (is_uniform)
uniform_src = c->defs[spill_temp]->src[0];
vir_for_each_inst_inorder_safe(inst, c) {
for (int i = 0; i < vir_get_nsrc(inst); i++) {
if (inst->src[i].file != QFILE_TEMP ||
inst->src[i].index != spill_temp) {
@ -204,23 +231,33 @@ v3d_spill_reg(struct v3d_compile *c, int spill_temp)
c->cursor = vir_before_inst(inst);
v3d_emit_spill_tmua(c, spill_offset);
vir_emit_thrsw(c);
inst->src[i] = vir_LDTMU(c);
c->fills++;
if (is_uniform) {
inst->src[i] = vir_MOV(c, uniform_src);
} else {
v3d_emit_spill_tmua(c, spill_offset);
vir_emit_thrsw(c);
inst->src[i] = vir_LDTMU(c);
c->fills++;
}
}
if (inst->dst.file == QFILE_TEMP &&
inst->dst.index == spill_temp) {
c->cursor = vir_after_inst(inst);
if (is_uniform) {
c->cursor.link = NULL;
vir_remove_instruction(c, inst);
} else {
c->cursor = vir_after_inst(inst);
inst->dst.index = c->num_temps++;
vir_MOV_dest(c, vir_reg(QFILE_MAGIC, V3D_QPU_WADDR_TMUD),
inst->dst);
v3d_emit_spill_tmua(c, spill_offset);
vir_emit_thrsw(c);
vir_TMUWT(c);
c->spills++;
inst->dst.index = c->num_temps++;
vir_MOV_dest(c, vir_reg(QFILE_MAGIC,
V3D_QPU_WADDR_TMUD),
inst->dst);
v3d_emit_spill_tmua(c, spill_offset);
vir_emit_thrsw(c);
vir_TMUWT(c);
c->spills++;
}
}
/* If we didn't have a last-thrsw inserted by nir_to_vir and
@ -228,7 +265,7 @@ v3d_spill_reg(struct v3d_compile *c, int spill_temp)
* right before we start the vpm/tlb sequence for the last
* thread segment.
*/
if (!last_thrsw && c->last_thrsw &&
if (!is_uniform && !last_thrsw && c->last_thrsw &&
(v3d_qpu_writes_vpm(&inst->qpu) ||
v3d_qpu_uses_tlb(&inst->qpu))) {
c->cursor = vir_before_inst(inst);