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
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@ -1152,4 +1152,8 @@ vir_BRANCH(struct v3d_compile *c, enum v3d_qpu_branch_cond cond)
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vir_for_each_block(_block, c) \
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vir_for_each_inst(inst, _block)
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#define vir_for_each_inst_inorder_safe(inst, c) \
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vir_for_each_block(_block, c) \
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vir_for_each_inst_safe(inst, _block)
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#endif /* V3D_COMPILER_H */
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@ -47,10 +47,21 @@ is_last_ldtmu(struct qinst *inst, struct qblock *block)
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return true;
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}
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static bool
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vir_is_mov_uniform(struct v3d_compile *c, int temp)
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{
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struct qinst *def = c->defs[temp];
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return (def &&
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vir_is_raw_mov(def) &&
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def->src[0].file == QFILE_UNIF);
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}
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static int
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v3d_choose_spill_node(struct v3d_compile *c, struct ra_graph *g,
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uint32_t *temp_to_node)
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{
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const float tmu_scale = 5;
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float block_scale = 1.0;
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float spill_costs[c->num_temps];
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bool in_tmu_operation = false;
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@ -75,22 +86,28 @@ v3d_choose_spill_node(struct v3d_compile *c, struct ra_graph *g,
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continue;
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int temp = inst->src[i].index;
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if (no_spilling) {
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BITSET_CLEAR(c->spillable,
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temp);
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} else {
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if (vir_is_mov_uniform(c, temp)) {
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spill_costs[temp] += block_scale;
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} else if (!no_spilling) {
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spill_costs[temp] += (block_scale *
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tmu_scale);
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} else {
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BITSET_CLEAR(c->spillable, temp);
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}
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}
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if (inst->dst.file == QFILE_TEMP) {
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int temp = inst->dst.index;
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if (no_spilling) {
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BITSET_CLEAR(c->spillable,
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temp);
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if (vir_is_mov_uniform(c, temp)) {
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/* We just rematerialize the unform
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* later.
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*/
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} else if (!no_spilling) {
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spill_costs[temp] += (block_scale *
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tmu_scale);
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} else {
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spill_costs[temp] += block_scale;
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BITSET_CLEAR(c->spillable, temp);
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}
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}
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@ -184,18 +201,28 @@ v3d_emit_spill_tmua(struct v3d_compile *c, uint32_t spill_offset)
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static void
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v3d_spill_reg(struct v3d_compile *c, int spill_temp)
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{
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uint32_t spill_offset = c->spill_size;
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c->spill_size += 16 * sizeof(uint32_t);
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bool is_uniform = vir_is_mov_uniform(c, spill_temp);
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if (spill_offset == 0)
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v3d_setup_spill_base(c);
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uint32_t spill_offset = 0;
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if (!is_uniform) {
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uint32_t spill_offset = c->spill_size;
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c->spill_size += 16 * sizeof(uint32_t);
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if (spill_offset == 0)
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v3d_setup_spill_base(c);
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}
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struct qinst *last_thrsw = c->last_thrsw;
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assert(!last_thrsw || last_thrsw->is_last_thrsw);
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int start_num_temps = c->num_temps;
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vir_for_each_inst_inorder(inst, c) {
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struct qreg uniform_src = c->undef;
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if (is_uniform)
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uniform_src = c->defs[spill_temp]->src[0];
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vir_for_each_inst_inorder_safe(inst, c) {
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for (int i = 0; i < vir_get_nsrc(inst); i++) {
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if (inst->src[i].file != QFILE_TEMP ||
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inst->src[i].index != spill_temp) {
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@ -204,23 +231,33 @@ v3d_spill_reg(struct v3d_compile *c, int spill_temp)
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c->cursor = vir_before_inst(inst);
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v3d_emit_spill_tmua(c, spill_offset);
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vir_emit_thrsw(c);
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inst->src[i] = vir_LDTMU(c);
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c->fills++;
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if (is_uniform) {
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inst->src[i] = vir_MOV(c, uniform_src);
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} else {
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v3d_emit_spill_tmua(c, spill_offset);
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vir_emit_thrsw(c);
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inst->src[i] = vir_LDTMU(c);
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c->fills++;
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}
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}
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if (inst->dst.file == QFILE_TEMP &&
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inst->dst.index == spill_temp) {
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c->cursor = vir_after_inst(inst);
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if (is_uniform) {
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c->cursor.link = NULL;
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vir_remove_instruction(c, inst);
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} else {
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c->cursor = vir_after_inst(inst);
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inst->dst.index = c->num_temps++;
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vir_MOV_dest(c, vir_reg(QFILE_MAGIC, V3D_QPU_WADDR_TMUD),
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inst->dst);
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v3d_emit_spill_tmua(c, spill_offset);
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vir_emit_thrsw(c);
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vir_TMUWT(c);
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c->spills++;
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inst->dst.index = c->num_temps++;
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vir_MOV_dest(c, vir_reg(QFILE_MAGIC,
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V3D_QPU_WADDR_TMUD),
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inst->dst);
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v3d_emit_spill_tmua(c, spill_offset);
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vir_emit_thrsw(c);
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vir_TMUWT(c);
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c->spills++;
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}
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}
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/* If we didn't have a last-thrsw inserted by nir_to_vir and
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@ -228,7 +265,7 @@ v3d_spill_reg(struct v3d_compile *c, int spill_temp)
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* right before we start the vpm/tlb sequence for the last
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* thread segment.
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*/
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if (!last_thrsw && c->last_thrsw &&
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if (!is_uniform && !last_thrsw && c->last_thrsw &&
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(v3d_qpu_writes_vpm(&inst->qpu) ||
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v3d_qpu_uses_tlb(&inst->qpu))) {
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c->cursor = vir_before_inst(inst);
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