/* * Copyright (C) 2018-2019 Alyssa Rosenzweig * Copyright (C) 2019 Collabora, Ltd. * * 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 "compiler.h" #include "midgard_ops.h" #include "util/u_math.h" #include "util/u_memory.h" #include "lcra.h" #include "midgard_quirks.h" struct phys_reg { /* Physical register: 0-31 */ unsigned reg; /* Byte offset into the physical register: 0-15 */ unsigned offset; /* Number of bytes in a component of this register */ unsigned size; }; /* Shift up by reg_offset and horizontally by dst_offset. */ static void offset_swizzle(unsigned *swizzle, unsigned reg_offset, unsigned srcsize, unsigned dst_offset) { unsigned out[MIR_VEC_COMPONENTS]; signed reg_comp = reg_offset / srcsize; signed dst_comp = dst_offset / srcsize; unsigned max_component = (16 / srcsize) - 1; assert(reg_comp * srcsize == reg_offset); assert(dst_comp * srcsize == dst_offset); for (signed c = 0; c < MIR_VEC_COMPONENTS; ++c) { signed comp = MAX2(c - dst_comp, 0); out[c] = MIN2(swizzle[comp] + reg_comp, max_component); } memcpy(swizzle, out, sizeof(out)); } /* Helper to return the default phys_reg for a given register */ static struct phys_reg default_phys_reg(int reg, midgard_reg_mode size) { struct phys_reg r = { .reg = reg, .offset = 0, .size = mir_bytes_for_mode(size) }; return r; } /* Determine which physical register, swizzle, and mask a virtual * register corresponds to */ static struct phys_reg index_to_reg(compiler_context *ctx, struct lcra_state *l, unsigned reg, midgard_reg_mode size) { /* Check for special cases */ if (reg == ~0) return default_phys_reg(REGISTER_UNUSED, size); else if (reg >= SSA_FIXED_MINIMUM) return default_phys_reg(SSA_REG_FROM_FIXED(reg), size); else if (!l) return default_phys_reg(REGISTER_UNUSED, size); struct phys_reg r = { .reg = l->solutions[reg] / 16, .offset = l->solutions[reg] & 0xF, .size = mir_bytes_for_mode(size) }; /* Report that we actually use this register, and return it */ if (r.reg < 16) ctx->work_registers = MAX2(ctx->work_registers, r.reg); return r; } static void set_class(unsigned *classes, unsigned node, unsigned class) { if (node < SSA_FIXED_MINIMUM && class != classes[node]) { assert(classes[node] == REG_CLASS_WORK); classes[node] = class; } } /* Special register classes impose special constraints on who can read their * values, so check that */ static bool check_read_class(unsigned *classes, unsigned tag, unsigned node) { /* Non-nodes are implicitly ok */ if (node >= SSA_FIXED_MINIMUM) return true; switch (classes[node]) { case REG_CLASS_LDST: return (tag == TAG_LOAD_STORE_4); case REG_CLASS_TEXR: return (tag == TAG_TEXTURE_4); case REG_CLASS_TEXW: return (tag != TAG_LOAD_STORE_4); case REG_CLASS_WORK: return IS_ALU(tag); default: unreachable("Invalid class"); } } static bool check_write_class(unsigned *classes, unsigned tag, unsigned node) { /* Non-nodes are implicitly ok */ if (node >= SSA_FIXED_MINIMUM) return true; switch (classes[node]) { case REG_CLASS_TEXR: return true; case REG_CLASS_TEXW: return (tag == TAG_TEXTURE_4); case REG_CLASS_LDST: case REG_CLASS_WORK: return IS_ALU(tag) || (tag == TAG_LOAD_STORE_4); default: unreachable("Invalid class"); } } /* Prepass before RA to ensure special class restrictions are met. The idea is * to create a bit field of types of instructions that read a particular index. * Later, we'll add moves as appropriate and rewrite to specialize by type. */ static void mark_node_class (unsigned *bitfield, unsigned node) { if (node < SSA_FIXED_MINIMUM) BITSET_SET(bitfield, node); } void mir_lower_special_reads(compiler_context *ctx) { size_t sz = BITSET_WORDS(ctx->temp_count) * sizeof(BITSET_WORD); /* Bitfields for the various types of registers we could have. aluw can * be written by either ALU or load/store */ unsigned *alur = calloc(sz, 1); unsigned *aluw = calloc(sz, 1); unsigned *brar = calloc(sz, 1); unsigned *ldst = calloc(sz, 1); unsigned *texr = calloc(sz, 1); unsigned *texw = calloc(sz, 1); /* Pass #1 is analysis, a linear scan to fill out the bitfields */ mir_foreach_instr_global(ctx, ins) { switch (ins->type) { case TAG_ALU_4: mark_node_class(aluw, ins->dest); mark_node_class(alur, ins->src[0]); mark_node_class(alur, ins->src[1]); mark_node_class(alur, ins->src[2]); if (ins->compact_branch && ins->writeout) mark_node_class(brar, ins->src[0]); break; case TAG_LOAD_STORE_4: mark_node_class(aluw, ins->dest); mark_node_class(ldst, ins->src[0]); mark_node_class(ldst, ins->src[1]); mark_node_class(ldst, ins->src[2]); break; case TAG_TEXTURE_4: mark_node_class(texr, ins->src[0]); mark_node_class(texr, ins->src[1]); mark_node_class(texr, ins->src[2]); mark_node_class(texw, ins->dest); break; } } /* Pass #2 is lowering now that we've analyzed all the classes. * Conceptually, if an index is only marked for a single type of use, * there is nothing to lower. If it is marked for different uses, we * split up based on the number of types of uses. To do so, we divide * into N distinct classes of use (where N>1 by definition), emit N-1 * moves from the index to copies of the index, and finally rewrite N-1 * of the types of uses to use the corresponding move */ unsigned spill_idx = ctx->temp_count; for (unsigned i = 0; i < ctx->temp_count; ++i) { bool is_alur = BITSET_TEST(alur, i); bool is_aluw = BITSET_TEST(aluw, i); bool is_brar = BITSET_TEST(brar, i); bool is_ldst = BITSET_TEST(ldst, i); bool is_texr = BITSET_TEST(texr, i); bool is_texw = BITSET_TEST(texw, i); /* Analyse to check how many distinct uses there are. ALU ops * (alur) can read the results of the texture pipeline (texw) * but not ldst or texr. Load/store ops (ldst) cannot read * anything but load/store inputs. Texture pipeline cannot read * anything but texture inputs. TODO: Simplify. */ bool collision = (is_alur && (is_ldst || is_texr)) || (is_ldst && (is_alur || is_texr || is_texw)) || (is_texr && (is_alur || is_ldst || is_texw)) || (is_texw && (is_aluw || is_ldst || is_texr)) || (is_brar && is_texw); if (!collision) continue; /* Use the index as-is as the work copy. Emit copies for * special uses */ unsigned classes[] = { TAG_LOAD_STORE_4, TAG_TEXTURE_4, TAG_TEXTURE_4, TAG_ALU_4}; bool collisions[] = { is_ldst, is_texr, is_texw && is_aluw, is_brar }; for (unsigned j = 0; j < ARRAY_SIZE(collisions); ++j) { if (!collisions[j]) continue; /* When the hazard is from reading, we move and rewrite * sources (typical case). When it's from writing, we * flip the move and rewrite destinations (obscure, * only from control flow -- impossible in SSA) */ bool hazard_write = (j == 2); unsigned idx = spill_idx++; midgard_instruction m = hazard_write ? v_mov(idx, i) : v_mov(i, idx); /* Insert move before each read/write, depending on the * hazard we're trying to account for */ mir_foreach_instr_global_safe(ctx, pre_use) { if (pre_use->type != classes[j]) continue; if (hazard_write) { if (pre_use->dest != i) continue; } else { if (!mir_has_arg(pre_use, i)) continue; } if (hazard_write) { midgard_instruction *use = mir_next_op(pre_use); assert(use); mir_insert_instruction_before(ctx, use, m); mir_rewrite_index_dst_single(pre_use, i, idx); } else { idx = spill_idx++; m = v_mov(i, idx); m.mask = mir_from_bytemask(mir_bytemask_of_read_components(pre_use, i), midgard_reg_mode_32); mir_insert_instruction_before(ctx, pre_use, m); mir_rewrite_index_src_single(pre_use, i, idx); } } } } free(alur); free(aluw); free(brar); free(ldst); free(texr); free(texw); } /* We register allocate after scheduling, so we need to ensure instructions * executing in parallel within a segment of a bundle don't clobber each * other's registers. This is mostly a non-issue thanks to scheduling, but * there are edge cases. In particular, after a register is written in a * segment, it interferes with anything reading. */ static void mir_compute_segment_interference( compiler_context *ctx, struct lcra_state *l, midgard_bundle *bun, unsigned pivot, unsigned i) { for (unsigned j = pivot; j < i; ++j) { mir_foreach_src(bun->instructions[j], s) { if (bun->instructions[j]->src[s] >= ctx->temp_count) continue; for (unsigned q = pivot; q < i; ++q) { if (bun->instructions[q]->dest >= ctx->temp_count) continue; /* See dEQP-GLES2.functional.shaders.return.output_write_in_func_dynamic_fragment */ if (q >= j) { if (!(bun->instructions[j]->unit == UNIT_SMUL && bun->instructions[q]->unit == UNIT_VLUT)) continue; } unsigned mask = mir_bytemask(bun->instructions[q]); unsigned rmask = mir_bytemask_of_read_components(bun->instructions[j], bun->instructions[j]->src[s]); lcra_add_node_interference(l, bun->instructions[q]->dest, mask, bun->instructions[j]->src[s], rmask); } } } } static void mir_compute_bundle_interference( compiler_context *ctx, struct lcra_state *l, midgard_bundle *bun) { if (!IS_ALU(bun->tag)) return; bool old = bun->instructions[0]->unit >= UNIT_VADD; unsigned pivot = 0; for (unsigned i = 1; i < bun->instruction_count; ++i) { bool new = bun->instructions[i]->unit >= UNIT_VADD; if (old != new) { mir_compute_segment_interference(ctx, l, bun, 0, i); pivot = i; break; } } mir_compute_segment_interference(ctx, l, bun, pivot, bun->instruction_count); } static void mir_compute_interference( compiler_context *ctx, struct lcra_state *l) { /* First, we need liveness information to be computed per block */ mir_compute_liveness(ctx); /* We need to force r1.w live throughout a blend shader */ if (ctx->is_blend) { unsigned r1w = ~0; mir_foreach_block(ctx, block) { mir_foreach_instr_in_block_rev(block, ins) { if (ins->writeout) r1w = ins->src[2]; } if (r1w != ~0) break; } mir_foreach_instr_global(ctx, ins) { if (ins->dest < ctx->temp_count) lcra_add_node_interference(l, ins->dest, mir_bytemask(ins), r1w, 0xF); } } /* Now that every block has live_in/live_out computed, we can determine * interference by walking each block linearly. Take live_out at the * end of each block and walk the block backwards. */ mir_foreach_block(ctx, blk) { uint16_t *live = mem_dup(blk->live_out, ctx->temp_count * sizeof(uint16_t)); mir_foreach_instr_in_block_rev(blk, ins) { /* Mark all registers live after the instruction as * interfering with the destination */ unsigned dest = ins->dest; if (dest < ctx->temp_count) { for (unsigned i = 0; i < ctx->temp_count; ++i) if (live[i]) { unsigned mask = mir_bytemask(ins); lcra_add_node_interference(l, dest, mask, i, live[i]); } } /* Update live_in */ mir_liveness_ins_update(live, ins, ctx->temp_count); } mir_foreach_bundle_in_block(blk, bun) mir_compute_bundle_interference(ctx, l, bun); free(live); } } /* This routine performs the actual register allocation. It should be succeeded * by install_registers */ static struct lcra_state * allocate_registers(compiler_context *ctx, bool *spilled) { /* The number of vec4 work registers available depends on when the * uniforms start, so compute that first */ int work_count = 16 - MAX2((ctx->uniform_cutoff - 8), 0); /* No register allocation to do with no SSA */ if (!ctx->temp_count) return NULL; struct lcra_state *l = lcra_alloc_equations(ctx->temp_count, 1, 8, 16, 5); /* Starts of classes, in bytes */ l->class_start[REG_CLASS_WORK] = 16 * 0; l->class_start[REG_CLASS_LDST] = 16 * 26; l->class_start[REG_CLASS_TEXR] = 16 * 28; l->class_start[REG_CLASS_TEXW] = 16 * 28; l->class_size[REG_CLASS_WORK] = 16 * work_count; l->class_size[REG_CLASS_LDST] = 16 * 2; l->class_size[REG_CLASS_TEXR] = 16 * 2; l->class_size[REG_CLASS_TEXW] = 16 * 2; lcra_set_disjoint_class(l, REG_CLASS_TEXR, REG_CLASS_TEXW); /* To save space on T*20, we don't have real texture registers. * Instead, tex inputs reuse the load/store pipeline registers, and * tex outputs use work r0/r1. Note we still use TEXR/TEXW classes, * noting that this handles interferences and sizes correctly. */ if (ctx->quirks & MIDGARD_INTERPIPE_REG_ALIASING) { l->class_start[REG_CLASS_TEXR] = l->class_start[REG_CLASS_LDST]; l->class_start[REG_CLASS_TEXW] = l->class_start[REG_CLASS_WORK]; } unsigned *found_class = calloc(sizeof(unsigned), ctx->temp_count); unsigned *min_alignment = calloc(sizeof(unsigned), ctx->temp_count); mir_foreach_instr_global(ctx, ins) { if (ins->dest >= SSA_FIXED_MINIMUM) continue; /* 0 for x, 1 for xy, 2 for xyz, 3 for xyzw */ int class = util_logbase2(ins->mask); /* Use the largest class if there's ambiguity, this * handles partial writes */ int dest = ins->dest; found_class[dest] = MAX2(found_class[dest], class); /* XXX: Ensure swizzles align the right way with more LCRA constraints? */ if (ins->type == TAG_ALU_4 && ins->alu.reg_mode != midgard_reg_mode_32) min_alignment[dest] = 3; /* (1 << 3) = 8 */ if (ins->type == TAG_LOAD_STORE_4 && ins->load_64) min_alignment[dest] = 3; /* We don't have a swizzle for the conditional and we don't * want to muck with the conditional itself, so just force * alignment for now */ if (ins->type == TAG_ALU_4 && OP_IS_CSEL_V(ins->alu.op)) min_alignment[dest] = 4; /* 1 << 4= 16-byte = vec4 */ } for (unsigned i = 0; i < ctx->temp_count; ++i) { lcra_set_alignment(l, i, min_alignment[i] ? min_alignment[i] : 2); lcra_restrict_range(l, i, (found_class[i] + 1) * 4); } free(found_class); free(min_alignment); /* Next, we'll determine semantic class. We default to zero (work). * But, if we're used with a special operation, that will force us to a * particular class. Each node must be assigned to exactly one class; a * prepass before RA should have lowered what-would-have-been * multiclass nodes into a series of moves to break it up into multiple * nodes (TODO) */ mir_foreach_instr_global(ctx, ins) { /* Check if this operation imposes any classes */ if (ins->type == TAG_LOAD_STORE_4) { set_class(l->class, ins->src[0], REG_CLASS_LDST); set_class(l->class, ins->src[1], REG_CLASS_LDST); set_class(l->class, ins->src[2], REG_CLASS_LDST); if (OP_IS_VEC4_ONLY(ins->load_store.op)) { lcra_restrict_range(l, ins->dest, 16); lcra_restrict_range(l, ins->src[0], 16); lcra_restrict_range(l, ins->src[1], 16); lcra_restrict_range(l, ins->src[2], 16); } } else if (ins->type == TAG_TEXTURE_4) { set_class(l->class, ins->dest, REG_CLASS_TEXW); set_class(l->class, ins->src[0], REG_CLASS_TEXR); set_class(l->class, ins->src[1], REG_CLASS_TEXR); set_class(l->class, ins->src[2], REG_CLASS_TEXR); set_class(l->class, ins->src[3], REG_CLASS_TEXR); /* Texture offsets need to be aligned to vec4, since * the swizzle for x is forced to x in hardware, while * the other components are free. TODO: Relax to 8 for * half-registers if that ever occurs. */ //lcra_restrict_range(l, ins->src[3], 16); } } /* Check that the semantics of the class are respected */ mir_foreach_instr_global(ctx, ins) { assert(check_write_class(l->class, ins->type, ins->dest)); assert(check_read_class(l->class, ins->type, ins->src[0])); assert(check_read_class(l->class, ins->type, ins->src[1])); assert(check_read_class(l->class, ins->type, ins->src[2])); } /* Mark writeout to r0, render target to r1.z, unknown to r1.w */ mir_foreach_instr_global(ctx, ins) { if (!(ins->compact_branch && ins->writeout)) continue; if (ins->src[0] < ctx->temp_count) l->solutions[ins->src[0]] = 0; if (ins->src[1] < ctx->temp_count) l->solutions[ins->src[1]] = (16 * 1) + COMPONENT_Z * 4; if (ins->src[2] < ctx->temp_count) l->solutions[ins->src[2]] = (16 * 1) + COMPONENT_W * 4; } mir_compute_interference(ctx, l); *spilled = !lcra_solve(l); return l; } /* Once registers have been decided via register allocation * (allocate_registers), we need to rewrite the MIR to use registers instead of * indices */ static void install_registers_instr( compiler_context *ctx, struct lcra_state *l, midgard_instruction *ins) { switch (ins->type) { case TAG_ALU_4: case TAG_ALU_8: case TAG_ALU_12: case TAG_ALU_16: { if (ins->compact_branch) return; struct phys_reg src1 = index_to_reg(ctx, l, ins->src[0], mir_srcsize(ins, 0)); struct phys_reg src2 = index_to_reg(ctx, l, ins->src[1], mir_srcsize(ins, 1)); struct phys_reg dest = index_to_reg(ctx, l, ins->dest, mir_typesize(ins)); mir_set_bytemask(ins, mir_bytemask(ins) << dest.offset); unsigned dest_offset = GET_CHANNEL_COUNT(alu_opcode_props[ins->alu.op].props) ? 0 : dest.offset; offset_swizzle(ins->swizzle[0], src1.offset, src1.size, dest_offset); ins->registers.src1_reg = src1.reg; ins->registers.src2_imm = ins->has_inline_constant; if (ins->has_inline_constant) { /* Encode inline 16-bit constant. See disassembler for * where the algorithm is from */ ins->registers.src2_reg = ins->inline_constant >> 11; int lower_11 = ins->inline_constant & ((1 << 12) - 1); uint16_t imm = ((lower_11 >> 8) & 0x7) | ((lower_11 & 0xFF) << 3); ins->alu.src2 = imm << 2; } else { midgard_vector_alu_src mod2 = vector_alu_from_unsigned(ins->alu.src2); offset_swizzle(ins->swizzle[1], src2.offset, src2.size, dest_offset); ins->alu.src2 = vector_alu_srco_unsigned(mod2); ins->registers.src2_reg = src2.reg; } ins->registers.out_reg = dest.reg; break; } case TAG_LOAD_STORE_4: { /* Which physical register we read off depends on * whether we are loading or storing -- think about the * logical dataflow */ bool encodes_src = OP_IS_STORE(ins->load_store.op); if (encodes_src) { struct phys_reg src = index_to_reg(ctx, l, ins->src[0], mir_srcsize(ins, 0)); assert(src.reg == 26 || src.reg == 27); ins->load_store.reg = src.reg - 26; offset_swizzle(ins->swizzle[0], src.offset, src.size, 0); } else { struct phys_reg dst = index_to_reg(ctx, l, ins->dest, mir_typesize(ins)); ins->load_store.reg = dst.reg; offset_swizzle(ins->swizzle[0], 0, 4, dst.offset); mir_set_bytemask(ins, mir_bytemask(ins) << dst.offset); } /* We also follow up by actual arguments */ unsigned src2 = ins->src[1]; unsigned src3 = ins->src[2]; if (src2 != ~0) { struct phys_reg src = index_to_reg(ctx, l, src2, mir_srcsize(ins, 1)); unsigned component = src.offset / src.size; assert(component * src.size == src.offset); ins->load_store.arg_1 |= midgard_ldst_reg(src.reg, component); } if (src3 != ~0) { struct phys_reg src = index_to_reg(ctx, l, src3, mir_srcsize(ins, 2)); unsigned component = src.offset / src.size; assert(component * src.size == src.offset); ins->load_store.arg_2 |= midgard_ldst_reg(src.reg, component); } break; } case TAG_TEXTURE_4: { /* Grab RA results */ struct phys_reg dest = index_to_reg(ctx, l, ins->dest, mir_typesize(ins)); struct phys_reg coord = index_to_reg(ctx, l, ins->src[1], mir_srcsize(ins, 1)); struct phys_reg lod = index_to_reg(ctx, l, ins->src[2], mir_srcsize(ins, 2)); struct phys_reg offset = index_to_reg(ctx, l, ins->src[3], mir_srcsize(ins, 2)); /* First, install the texture coordinate */ ins->texture.in_reg_full = 1; ins->texture.in_reg_upper = 0; ins->texture.in_reg_select = coord.reg & 1; offset_swizzle(ins->swizzle[1], coord.offset, coord.size, 0); /* Next, install the destination */ ins->texture.out_full = 1; ins->texture.out_upper = 0; ins->texture.out_reg_select = dest.reg & 1; offset_swizzle(ins->swizzle[0], 0, 4, dest.offset); mir_set_bytemask(ins, mir_bytemask(ins) << dest.offset); /* If there is a register LOD/bias, use it */ if (ins->src[2] != ~0) { assert(!(lod.offset & 3)); midgard_tex_register_select sel = { .select = lod.reg & 1, .full = 1, .component = lod.offset / 4 }; uint8_t packed; memcpy(&packed, &sel, sizeof(packed)); ins->texture.bias = packed; } /* If there is an offset register, install it */ if (ins->src[3] != ~0) { unsigned x = offset.offset / 4; unsigned y = x + 1; unsigned z = x + 2; /* Check range, TODO: half-registers */ assert(z < 4); ins->texture.offset = (1) | /* full */ (offset.reg & 1) << 1 | /* select */ (0 << 2) | /* upper */ (x << 3) | /* swizzle */ (y << 5) | /* swizzle */ (z << 7); /* swizzle */ } break; } default: break; } } static void install_registers(compiler_context *ctx, struct lcra_state *l) { mir_foreach_instr_global(ctx, ins) install_registers_instr(ctx, l, ins); } /* If register allocation fails, find the best spill node */ static signed mir_choose_spill_node( compiler_context *ctx, struct lcra_state *l) { /* We can't spill a previously spilled value or an unspill */ mir_foreach_instr_global(ctx, ins) { if (ins->no_spill & (1 << l->spill_class)) { lcra_set_node_spill_cost(l, ins->dest, -1); if (l->spill_class != REG_CLASS_WORK) { mir_foreach_src(ins, s) lcra_set_node_spill_cost(l, ins->src[s], -1); } } } return lcra_get_best_spill_node(l); } /* Once we've chosen a spill node, spill it */ static void mir_spill_register( compiler_context *ctx, unsigned spill_node, unsigned spill_class, unsigned *spill_count) { unsigned spill_index = ctx->temp_count; /* We have a spill node, so check the class. Work registers * legitimately spill to TLS, but special registers just spill to work * registers */ bool is_special = spill_class != REG_CLASS_WORK; bool is_special_w = spill_class == REG_CLASS_TEXW; /* Allocate TLS slot (maybe) */ unsigned spill_slot = !is_special ? (*spill_count)++ : 0; /* For TLS, replace all stores to the spilled node. For * special reads, just keep as-is; the class will be demoted * implicitly. For special writes, spill to a work register */ if (!is_special || is_special_w) { if (is_special_w) spill_slot = spill_index++; mir_foreach_block(ctx, block) { mir_foreach_instr_in_block_safe(block, ins) { if (ins->dest != spill_node) continue; midgard_instruction st; if (is_special_w) { st = v_mov(spill_node, spill_slot); st.no_spill |= (1 << spill_class); } else { ins->dest = spill_index++; ins->no_spill |= (1 << spill_class); st = v_load_store_scratch(ins->dest, spill_slot, true, ins->mask); } /* Hint: don't rewrite this node */ st.hint = true; mir_insert_instruction_after_scheduled(ctx, block, ins, st); if (!is_special) ctx->spills++; } } } /* For special reads, figure out how many bytes we need */ unsigned read_bytemask = 0; mir_foreach_instr_global_safe(ctx, ins) { read_bytemask |= mir_bytemask_of_read_components(ins, spill_node); } /* Insert a load from TLS before the first consecutive * use of the node, rewriting to use spilled indices to * break up the live range. Or, for special, insert a * move. Ironically the latter *increases* register * pressure, but the two uses of the spilling mechanism * are somewhat orthogonal. (special spilling is to use * work registers to back special registers; TLS * spilling is to use memory to back work registers) */ mir_foreach_block(ctx, block) { mir_foreach_instr_in_block(block, ins) { /* We can't rewrite the moves used to spill in the * first place. These moves are hinted. */ if (ins->hint) continue; /* If we don't use the spilled value, nothing to do */ if (!mir_has_arg(ins, spill_node)) continue; unsigned index = 0; if (!is_special_w) { index = ++spill_index; midgard_instruction *before = ins; midgard_instruction st; if (is_special) { /* Move */ st = v_mov(spill_node, index); st.no_spill |= (1 << spill_class); } else { /* TLS load */ st = v_load_store_scratch(index, spill_slot, false, 0xF); } /* Mask the load based on the component count * actually needed to prevent RA loops */ st.mask = mir_from_bytemask(read_bytemask, midgard_reg_mode_32); mir_insert_instruction_before_scheduled(ctx, block, before, st); } else { /* Special writes already have their move spilled in */ index = spill_slot; } /* Rewrite to use */ mir_rewrite_index_src_single(ins, spill_node, index); if (!is_special) ctx->fills++; } } /* Reset hints */ mir_foreach_instr_global(ctx, ins) { ins->hint = false; } } /* Run register allocation in a loop, spilling until we succeed */ void mir_ra(compiler_context *ctx) { struct lcra_state *l = NULL; bool spilled = false; int iter_count = 1000; /* max iterations */ /* Number of 128-bit slots in memory we've spilled into */ unsigned spill_count = 0; mir_create_pipeline_registers(ctx); do { if (spilled) { signed spill_node = mir_choose_spill_node(ctx, l); if (spill_node == -1) { fprintf(stderr, "ERROR: Failed to choose spill node\n"); return; } mir_spill_register(ctx, spill_node, l->spill_class, &spill_count); } mir_squeeze_index(ctx); mir_invalidate_liveness(ctx); if (l) { lcra_free(l); l = NULL; } l = allocate_registers(ctx, &spilled); } while(spilled && ((iter_count--) > 0)); if (iter_count <= 0) { fprintf(stderr, "panfrost: Gave up allocating registers, rendering will be incomplete\n"); assert(0); } /* Report spilling information. spill_count is in 128-bit slots (vec4 x * fp32), but tls_size is in bytes, so multiply by 16 */ ctx->tls_size = spill_count * 16; install_registers(ctx, l); lcra_free(l); }