/* * 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 * */ #include "brw_eu.h" #include "brw_fs.h" #include "brw_cfg.h" #include "util/register_allocate.h" using namespace brw; static void assign_reg(unsigned *reg_hw_locations, fs_reg *reg) { if (reg->file == VGRF) { reg->nr = reg_hw_locations[reg->nr] + reg->offset / REG_SIZE; reg->offset %= REG_SIZE; } } void fs_visitor::assign_regs_trivial() { unsigned hw_reg_mapping[this->alloc.count + 1]; unsigned i; int reg_width = dispatch_width / 8; /* Note that compressed instructions require alignment to 2 registers. */ hw_reg_mapping[0] = ALIGN(this->first_non_payload_grf, reg_width); for (i = 1; i <= this->alloc.count; i++) { hw_reg_mapping[i] = (hw_reg_mapping[i - 1] + this->alloc.sizes[i - 1]); } this->grf_used = hw_reg_mapping[this->alloc.count]; foreach_block_and_inst(block, fs_inst, inst, cfg) { assign_reg(hw_reg_mapping, &inst->dst); for (i = 0; i < inst->sources; i++) { assign_reg(hw_reg_mapping, &inst->src[i]); } } if (this->grf_used >= max_grf) { fail("Ran out of regs on trivial allocator (%d/%d)\n", this->grf_used, max_grf); } else { this->alloc.count = this->grf_used; } } static void brw_alloc_reg_set(struct brw_compiler *compiler, int dispatch_width) { const struct gen_device_info *devinfo = compiler->devinfo; int base_reg_count = BRW_MAX_GRF; const int index = _mesa_logbase2(dispatch_width / 8); if (dispatch_width > 8 && devinfo->gen >= 7) { /* For IVB+, we don't need the PLN hacks or the even-reg alignment in * SIMD16. Therefore, we can use the exact same register sets for * SIMD16 as we do for SIMD8 and we don't need to recalculate them. */ compiler->fs_reg_sets[index] = compiler->fs_reg_sets[0]; return; } /* The registers used to make up almost all values handled in the compiler * are a scalar value occupying a single register (or 2 registers in the * case of SIMD16, which is handled by dividing base_reg_count by 2 and * multiplying allocated register numbers by 2). Things that were * aggregates of scalar values at the GLSL level were split to scalar * values by split_virtual_grfs(). * * However, texture SEND messages return a series of contiguous registers * to write into. We currently always ask for 4 registers, but we may * convert that to use less some day. * * Additionally, on gen5 we need aligned pairs of registers for the PLN * instruction, and on gen4 we need 8 contiguous regs for workaround simd16 * texturing. */ const int class_count = MAX_VGRF_SIZE; int class_sizes[MAX_VGRF_SIZE]; for (unsigned i = 0; i < MAX_VGRF_SIZE; i++) class_sizes[i] = i + 1; memset(compiler->fs_reg_sets[index].class_to_ra_reg_range, 0, sizeof(compiler->fs_reg_sets[index].class_to_ra_reg_range)); int *class_to_ra_reg_range = compiler->fs_reg_sets[index].class_to_ra_reg_range; /* Compute the total number of registers across all classes. */ int ra_reg_count = 0; for (int i = 0; i < class_count; i++) { if (devinfo->gen <= 5 && dispatch_width >= 16) { /* From the G45 PRM: * * In order to reduce the hardware complexity, the following * rules and restrictions apply to the compressed instruction: * ... * * Operand Alignment Rule: With the exceptions listed below, a * source/destination operand in general should be aligned to * even 256-bit physical register with a region size equal to * two 256-bit physical register */ ra_reg_count += (base_reg_count - (class_sizes[i] - 1)) / 2; } else { ra_reg_count += base_reg_count - (class_sizes[i] - 1); } /* Mark the last register. We'll fill in the beginnings later. */ class_to_ra_reg_range[class_sizes[i]] = ra_reg_count; } /* Fill out the rest of the range markers */ for (int i = 1; i < 17; ++i) { if (class_to_ra_reg_range[i] == 0) class_to_ra_reg_range[i] = class_to_ra_reg_range[i-1]; } uint8_t *ra_reg_to_grf = ralloc_array(compiler, uint8_t, ra_reg_count); struct ra_regs *regs = ra_alloc_reg_set(compiler, ra_reg_count, false); if (devinfo->gen >= 6) ra_set_allocate_round_robin(regs); int *classes = ralloc_array(compiler, int, class_count); int aligned_pairs_class = -1; /* Allocate space for q values. We allocate class_count + 1 because we * want to leave room for the aligned pairs class if we have it. */ unsigned int **q_values = ralloc_array(compiler, unsigned int *, class_count + 1); for (int i = 0; i < class_count + 1; ++i) q_values[i] = ralloc_array(q_values, unsigned int, class_count + 1); /* Now, add the registers to their classes, and add the conflicts * between them and the base GRF registers (and also each other). */ int reg = 0; int pairs_base_reg = 0; int pairs_reg_count = 0; for (int i = 0; i < class_count; i++) { int class_reg_count; if (devinfo->gen <= 5 && dispatch_width >= 16) { class_reg_count = (base_reg_count - (class_sizes[i] - 1)) / 2; /* See comment below. The only difference here is that we are * dealing with pairs of registers instead of single registers. * Registers of odd sizes simply get rounded up. */ for (int j = 0; j < class_count; j++) q_values[i][j] = (class_sizes[i] + 1) / 2 + (class_sizes[j] + 1) / 2 - 1; } else { class_reg_count = base_reg_count - (class_sizes[i] - 1); /* From register_allocate.c: * * q(B,C) (indexed by C, B is this register class) in * Runeson/Nyström paper. This is "how many registers of B could * the worst choice register from C conflict with". * * If we just let the register allocation algorithm compute these * values, is extremely expensive. However, since all of our * registers are laid out, we can very easily compute them * ourselves. View the register from C as fixed starting at GRF n * somwhere in the middle, and the register from B as sliding back * and forth. Then the first register to conflict from B is the * one starting at n - class_size[B] + 1 and the last register to * conflict will start at n + class_size[B] - 1. Therefore, the * number of conflicts from B is class_size[B] + class_size[C] - 1. * * +-+-+-+-+-+-+ +-+-+-+-+-+-+ * B | | | | | |n| --> | | | | | | | * +-+-+-+-+-+-+ +-+-+-+-+-+-+ * +-+-+-+-+-+ * C |n| | | | | * +-+-+-+-+-+ */ for (int j = 0; j < class_count; j++) q_values[i][j] = class_sizes[i] + class_sizes[j] - 1; } classes[i] = ra_alloc_reg_class(regs); /* Save this off for the aligned pair class at the end. */ if (class_sizes[i] == 2) { pairs_base_reg = reg; pairs_reg_count = class_reg_count; } if (devinfo->gen <= 5 && dispatch_width >= 16) { for (int j = 0; j < class_reg_count; j++) { ra_class_add_reg(regs, classes[i], reg); ra_reg_to_grf[reg] = j * 2; for (int base_reg = j; base_reg < j + (class_sizes[i] + 1) / 2; base_reg++) { ra_add_reg_conflict(regs, base_reg, reg); } reg++; } } else { for (int j = 0; j < class_reg_count; j++) { ra_class_add_reg(regs, classes[i], reg); ra_reg_to_grf[reg] = j; for (int base_reg = j; base_reg < j + class_sizes[i]; base_reg++) { ra_add_reg_conflict(regs, base_reg, reg); } reg++; } } } assert(reg == ra_reg_count); /* Applying transitivity to all of the base registers gives us the * appropreate register conflict relationships everywhere. */ for (int reg = 0; reg < base_reg_count; reg++) ra_make_reg_conflicts_transitive(regs, reg); /* Add a special class for aligned pairs, which we'll put delta_xy * in on Gen <= 6 so that we can do PLN. */ if (devinfo->has_pln && dispatch_width == 8 && devinfo->gen <= 6) { aligned_pairs_class = ra_alloc_reg_class(regs); for (int i = 0; i < pairs_reg_count; i++) { if ((ra_reg_to_grf[pairs_base_reg + i] & 1) == 0) { ra_class_add_reg(regs, aligned_pairs_class, pairs_base_reg + i); } } for (int i = 0; i < class_count; i++) { /* These are a little counter-intuitive because the pair registers * are required to be aligned while the register they are * potentially interferring with are not. In the case where the * size is even, the worst-case is that the register is * odd-aligned. In the odd-size case, it doesn't matter. */ q_values[class_count][i] = class_sizes[i] / 2 + 1; q_values[i][class_count] = class_sizes[i] + 1; } q_values[class_count][class_count] = 1; } ra_set_finalize(regs, q_values); ralloc_free(q_values); compiler->fs_reg_sets[index].regs = regs; for (unsigned i = 0; i < ARRAY_SIZE(compiler->fs_reg_sets[index].classes); i++) compiler->fs_reg_sets[index].classes[i] = -1; for (int i = 0; i < class_count; i++) compiler->fs_reg_sets[index].classes[class_sizes[i] - 1] = classes[i]; compiler->fs_reg_sets[index].ra_reg_to_grf = ra_reg_to_grf; compiler->fs_reg_sets[index].aligned_pairs_class = aligned_pairs_class; } void brw_fs_alloc_reg_sets(struct brw_compiler *compiler) { brw_alloc_reg_set(compiler, 8); brw_alloc_reg_set(compiler, 16); brw_alloc_reg_set(compiler, 32); } static int count_to_loop_end(const bblock_t *block) { if (block->end()->opcode == BRW_OPCODE_WHILE) return block->end_ip; int depth = 1; /* Skip the first block, since we don't want to count the do the calling * function found. */ for (block = block->next(); depth > 0; block = block->next()) { if (block->start()->opcode == BRW_OPCODE_DO) depth++; if (block->end()->opcode == BRW_OPCODE_WHILE) { depth--; if (depth == 0) return block->end_ip; } } unreachable("not reached"); } void fs_visitor::calculate_payload_ranges(int payload_node_count, int *payload_last_use_ip) { int loop_depth = 0; int loop_end_ip = 0; for (int i = 0; i < payload_node_count; i++) payload_last_use_ip[i] = -1; int ip = 0; foreach_block_and_inst(block, fs_inst, inst, cfg) { switch (inst->opcode) { case BRW_OPCODE_DO: loop_depth++; /* Since payload regs are deffed only at the start of the shader * execution, any uses of the payload within a loop mean the live * interval extends to the end of the outermost loop. Find the ip of * the end now. */ if (loop_depth == 1) loop_end_ip = count_to_loop_end(block); break; case BRW_OPCODE_WHILE: loop_depth--; break; default: break; } int use_ip; if (loop_depth > 0) use_ip = loop_end_ip; else use_ip = ip; /* Note that UNIFORM args have been turned into FIXED_GRF by * assign_curbe_setup(), and interpolation uses fixed hardware regs from * the start (see interp_reg()). */ for (int i = 0; i < inst->sources; i++) { if (inst->src[i].file == FIXED_GRF) { int node_nr = inst->src[i].nr; if (node_nr >= payload_node_count) continue; for (unsigned j = 0; j < regs_read(inst, i); j++) { payload_last_use_ip[node_nr + j] = use_ip; assert(node_nr + j < unsigned(payload_node_count)); } } } /* Special case instructions which have extra implied registers used. */ switch (inst->opcode) { case CS_OPCODE_CS_TERMINATE: payload_last_use_ip[0] = use_ip; break; default: if (inst->eot) { /* We could omit this for the !inst->header_present case, except * that the simulator apparently incorrectly reads from g0/g1 * instead of sideband. It also really freaks out driver * developers to see g0 used in unusual places, so just always * reserve it. */ payload_last_use_ip[0] = use_ip; payload_last_use_ip[1] = use_ip; } break; } ip++; } } /** * Sets up interference between thread payload registers and the virtual GRFs * to be allocated for program temporaries. * * We want to be able to reallocate the payload for our virtual GRFs, notably * because the setup coefficients for a full set of 16 FS inputs takes up 8 of * our 128 registers. * * The layout of the payload registers is: * * 0..payload.num_regs-1: fixed function setup (including bary coordinates). * payload.num_regs..payload.num_regs+curb_read_lengh-1: uniform data * payload.num_regs+curb_read_lengh..first_non_payload_grf-1: setup coefficients. * * And we have payload_node_count nodes covering these registers in order * (note that in SIMD16, a node is two registers). */ void fs_visitor::setup_payload_interference(struct ra_graph *g, int payload_node_count, int first_payload_node) { int payload_last_use_ip[payload_node_count]; calculate_payload_ranges(payload_node_count, payload_last_use_ip); for (int i = 0; i < payload_node_count; i++) { if (payload_last_use_ip[i] == -1) continue; /* Mark the payload node as interfering with any virtual grf that is * live between the start of the program and our last use of the payload * node. */ for (unsigned j = 0; j < this->alloc.count; j++) { /* Note that we use a <= comparison, unlike virtual_grf_interferes(), * in order to not have to worry about the uniform issue described in * calculate_live_intervals(). */ if (this->virtual_grf_start[j] <= payload_last_use_ip[i]) { ra_add_node_interference(g, first_payload_node + i, j); } } } for (int i = 0; i < payload_node_count; i++) { /* Mark each payload node as being allocated to its physical register. * * The alternative would be to have per-physical-register classes, which * would just be silly. */ if (devinfo->gen <= 5 && dispatch_width >= 16) { /* We have to divide by 2 here because we only have even numbered * registers. Some of the payload registers will be odd, but * that's ok because their physical register numbers have already * been assigned. The only thing this is used for is interference. */ ra_set_node_reg(g, first_payload_node + i, i / 2); } else { ra_set_node_reg(g, first_payload_node + i, i); } } } /** * Sets the mrf_used array to indicate which MRFs are used by the shader IR * * This is used in assign_regs() to decide which of the GRFs that we use as * MRFs on gen7 get normally register allocated, and in register spilling to * see if we can actually use MRFs to do spills without overwriting normal MRF * contents. */ static void get_used_mrfs(fs_visitor *v, bool *mrf_used) { int reg_width = v->dispatch_width / 8; memset(mrf_used, 0, BRW_MAX_MRF(v->devinfo->gen) * sizeof(bool)); foreach_block_and_inst(block, fs_inst, inst, v->cfg) { if (inst->dst.file == MRF) { int reg = inst->dst.nr & ~BRW_MRF_COMPR4; mrf_used[reg] = true; if (reg_width == 2) { if (inst->dst.nr & BRW_MRF_COMPR4) { mrf_used[reg + 4] = true; } else { mrf_used[reg + 1] = true; } } } if (inst->mlen > 0) { for (int i = 0; i < v->implied_mrf_writes(inst); i++) { mrf_used[inst->base_mrf + i] = true; } } } } /** * Sets interference between virtual GRFs and usage of the high GRFs for SEND * messages (treated as MRFs in code generation). */ static void setup_mrf_hack_interference(fs_visitor *v, struct ra_graph *g, int first_mrf_node, int *first_used_mrf) { bool mrf_used[BRW_MAX_MRF(v->devinfo->gen)]; get_used_mrfs(v, mrf_used); *first_used_mrf = BRW_MAX_MRF(v->devinfo->gen); for (int i = 0; i < BRW_MAX_MRF(v->devinfo->gen); i++) { /* Mark each MRF reg node as being allocated to its physical register. * * The alternative would be to have per-physical-register classes, which * would just be silly. */ ra_set_node_reg(g, first_mrf_node + i, GEN7_MRF_HACK_START + i); /* Since we don't have any live/dead analysis on the MRFs, just mark all * that are used as conflicting with all virtual GRFs. */ if (mrf_used[i]) { if (i < *first_used_mrf) *first_used_mrf = i; for (unsigned j = 0; j < v->alloc.count; j++) { ra_add_node_interference(g, first_mrf_node + i, j); } } } } bool fs_visitor::assign_regs(bool allow_spilling, bool spill_all) { /* Most of this allocation was written for a reg_width of 1 * (dispatch_width == 8). In extending to SIMD16, the code was * left in place and it was converted to have the hardware * registers it's allocating be contiguous physical pairs of regs * for reg_width == 2. */ int reg_width = dispatch_width / 8; unsigned hw_reg_mapping[this->alloc.count]; int payload_node_count = ALIGN(this->first_non_payload_grf, reg_width); int rsi = _mesa_logbase2(reg_width); /* Which compiler->fs_reg_sets[] to use */ calculate_live_intervals(); int node_count = this->alloc.count; int first_payload_node = node_count; node_count += payload_node_count; int first_mrf_hack_node = node_count; if (devinfo->gen >= 7) node_count += BRW_MAX_GRF - GEN7_MRF_HACK_START; struct ra_graph *g = ra_alloc_interference_graph(compiler->fs_reg_sets[rsi].regs, node_count); for (unsigned i = 0; i < this->alloc.count; i++) { unsigned size = this->alloc.sizes[i]; int c; assert(size <= ARRAY_SIZE(compiler->fs_reg_sets[rsi].classes) && "Register allocation relies on split_virtual_grfs()"); c = compiler->fs_reg_sets[rsi].classes[size - 1]; /* Special case: on pre-GEN6 hardware that supports PLN, the * second operand of a PLN instruction needs to be an * even-numbered register, so we have a special register class * wm_aligned_pairs_class to handle this case. pre-GEN6 always * uses this->delta_xy[BRW_BARYCENTRIC_PERSPECTIVE_PIXEL] as the * second operand of a PLN instruction (since it doesn't support * any other interpolation modes). So all we need to do is find * that register and set it to the appropriate class. */ if (compiler->fs_reg_sets[rsi].aligned_pairs_class >= 0 && this->delta_xy[BRW_BARYCENTRIC_PERSPECTIVE_PIXEL].file == VGRF && this->delta_xy[BRW_BARYCENTRIC_PERSPECTIVE_PIXEL].nr == i) { c = compiler->fs_reg_sets[rsi].aligned_pairs_class; } ra_set_node_class(g, i, c); for (unsigned j = 0; j < i; j++) { if (virtual_grf_interferes(i, j)) { ra_add_node_interference(g, i, j); } } } /* Certain instructions can't safely use the same register for their * sources and destination. Add interference. */ foreach_block_and_inst(block, fs_inst, inst, cfg) { if (inst->dst.file == VGRF && inst->has_source_and_destination_hazard()) { for (unsigned i = 0; i < 3; i++) { if (inst->src[i].file == VGRF) { ra_add_node_interference(g, inst->dst.nr, inst->src[i].nr); } } } } setup_payload_interference(g, payload_node_count, first_payload_node); if (devinfo->gen >= 7) { int first_used_mrf = BRW_MAX_MRF(devinfo->gen); setup_mrf_hack_interference(this, g, first_mrf_hack_node, &first_used_mrf); foreach_block_and_inst(block, fs_inst, inst, cfg) { /* When we do send-from-GRF for FB writes, we need to ensure that * the last write instruction sends from a high register. This is * because the vertex fetcher wants to start filling the low * payload registers while the pixel data port is still working on * writing out the memory. If we don't do this, we get rendering * artifacts. * * We could just do "something high". Instead, we just pick the * highest register that works. */ if (inst->eot) { int size = alloc.sizes[inst->src[0].nr]; int reg = compiler->fs_reg_sets[rsi].class_to_ra_reg_range[size] - 1; /* If something happened to spill, we want to push the EOT send * register early enough in the register file that we don't * conflict with any used MRF hack registers. */ reg -= BRW_MAX_MRF(devinfo->gen) - first_used_mrf; ra_set_node_reg(g, inst->src[0].nr, reg); break; } } } if (dispatch_width > 8) { /* In 16-wide dispatch we have an issue where a compressed * instruction is actually two instructions executed simultaneiously. * It's actually ok to have the source and destination registers be * the same. In this case, each instruction over-writes its own * source and there's no problem. The real problem here is if the * source and destination registers are off by one. Then you can end * up in a scenario where the first instruction over-writes the * source of the second instruction. Since the compiler doesn't know * about this level of granularity, we simply make the source and * destination interfere. */ foreach_block_and_inst(block, fs_inst, inst, cfg) { if (inst->dst.file != VGRF) continue; for (int i = 0; i < inst->sources; ++i) { if (inst->src[i].file == VGRF) { ra_add_node_interference(g, inst->dst.nr, inst->src[i].nr); } } } } /* Debug of register spilling: Go spill everything. */ if (unlikely(spill_all)) { int reg = choose_spill_reg(g); if (reg != -1) { spill_reg(reg); ralloc_free(g); return false; } } if (!ra_allocate(g)) { /* Failed to allocate registers. Spill a reg, and the caller will * loop back into here to try again. */ int reg = choose_spill_reg(g); if (reg == -1) { fail("no register to spill:\n"); dump_instructions(NULL); } else if (allow_spilling) { spill_reg(reg); } ralloc_free(g); return false; } /* Get the chosen virtual registers for each node, and map virtual * regs in the register classes back down to real hardware reg * numbers. */ this->grf_used = payload_node_count; for (unsigned i = 0; i < this->alloc.count; i++) { int reg = ra_get_node_reg(g, i); hw_reg_mapping[i] = compiler->fs_reg_sets[rsi].ra_reg_to_grf[reg]; this->grf_used = MAX2(this->grf_used, hw_reg_mapping[i] + this->alloc.sizes[i]); } foreach_block_and_inst(block, fs_inst, inst, cfg) { assign_reg(hw_reg_mapping, &inst->dst); for (int i = 0; i < inst->sources; i++) { assign_reg(hw_reg_mapping, &inst->src[i]); } } this->alloc.count = this->grf_used; ralloc_free(g); return true; } namespace { /** * Maximum spill block size we expect to encounter in 32B units. * * This is somewhat arbitrary and doesn't necessarily limit the maximum * variable size that can be spilled -- A higher value will allow a * variable of a given size to be spilled more efficiently with a smaller * number of scratch messages, but will increase the likelihood of a * collision between the MRFs reserved for spilling and other MRFs used by * the program (and possibly increase GRF register pressure on platforms * without hardware MRFs), what could cause register allocation to fail. * * For the moment reserve just enough space so a register of 32 bit * component type and natural region width can be spilled without splitting * into multiple (force_writemask_all) scratch messages. */ unsigned spill_max_size(const backend_shader *s) { /* FINISHME - On Gen7+ it should be possible to avoid this limit * altogether by spilling directly from the temporary GRF * allocated to hold the result of the instruction (and the * scratch write header). */ /* FINISHME - The shader's dispatch width probably belongs in * backend_shader (or some nonexistent fs_shader class?) * rather than in the visitor class. */ return static_cast(s)->dispatch_width / 8; } /** * First MRF register available for spilling. */ unsigned spill_base_mrf(const backend_shader *s) { return BRW_MAX_MRF(s->devinfo->gen) - spill_max_size(s) - 1; } } static void emit_unspill(const fs_builder &bld, fs_reg dst, uint32_t spill_offset, unsigned count) { const gen_device_info *devinfo = bld.shader->devinfo; const unsigned reg_size = dst.component_size(bld.dispatch_width()) / REG_SIZE; assert(count % reg_size == 0); for (unsigned i = 0; i < count / reg_size; i++) { /* The Gen7 descriptor-based offset is 12 bits of HWORD units. Because * the Gen7-style scratch block read is hardwired to BTI 255, on Gen9+ * it would cause the DC to do an IA-coherent read, what largely * outweighs the slight advantage from not having to provide the address * as part of the message header, so we're better off using plain old * oword block reads. */ bool gen7_read = (devinfo->gen >= 7 && devinfo->gen < 9 && spill_offset < (1 << 12) * REG_SIZE); fs_inst *unspill_inst = bld.emit(gen7_read ? SHADER_OPCODE_GEN7_SCRATCH_READ : SHADER_OPCODE_GEN4_SCRATCH_READ, dst); unspill_inst->offset = spill_offset; if (!gen7_read) { unspill_inst->base_mrf = spill_base_mrf(bld.shader); unspill_inst->mlen = 1; /* header contains offset */ } dst.offset += reg_size * REG_SIZE; spill_offset += reg_size * REG_SIZE; } } static void emit_spill(const fs_builder &bld, fs_reg src, uint32_t spill_offset, unsigned count) { const unsigned reg_size = src.component_size(bld.dispatch_width()) / REG_SIZE; assert(count % reg_size == 0); for (unsigned i = 0; i < count / reg_size; i++) { fs_inst *spill_inst = bld.emit(SHADER_OPCODE_GEN4_SCRATCH_WRITE, bld.null_reg_f(), src); src.offset += reg_size * REG_SIZE; spill_inst->offset = spill_offset + i * reg_size * REG_SIZE; spill_inst->mlen = 1 + reg_size; /* header, value */ spill_inst->base_mrf = spill_base_mrf(bld.shader); } } int fs_visitor::choose_spill_reg(struct ra_graph *g) { float block_scale = 1.0; float spill_costs[this->alloc.count]; bool no_spill[this->alloc.count]; for (unsigned i = 0; i < this->alloc.count; i++) { spill_costs[i] = 0.0; no_spill[i] = false; } /* Calculate costs for spilling nodes. Call it a cost of 1 per * spill/unspill we'll have to do, and guess that the insides of * loops run 10 times. */ foreach_block_and_inst(block, fs_inst, inst, cfg) { for (unsigned int i = 0; i < inst->sources; i++) { if (inst->src[i].file == VGRF) spill_costs[inst->src[i].nr] += regs_read(inst, i) * block_scale; } if (inst->dst.file == VGRF) spill_costs[inst->dst.nr] += regs_written(inst) * block_scale; switch (inst->opcode) { case BRW_OPCODE_DO: block_scale *= 10; break; case BRW_OPCODE_WHILE: block_scale /= 10; break; case BRW_OPCODE_IF: case BRW_OPCODE_IFF: block_scale *= 0.5; break; case BRW_OPCODE_ENDIF: block_scale /= 0.5; break; case SHADER_OPCODE_GEN4_SCRATCH_WRITE: if (inst->src[0].file == VGRF) no_spill[inst->src[0].nr] = true; break; case SHADER_OPCODE_GEN4_SCRATCH_READ: case SHADER_OPCODE_GEN7_SCRATCH_READ: if (inst->dst.file == VGRF) no_spill[inst->dst.nr] = true; break; default: break; } } for (unsigned i = 0; i < this->alloc.count; i++) { if (!no_spill[i]) ra_set_node_spill_cost(g, i, spill_costs[i]); } return ra_get_best_spill_node(g); } void fs_visitor::spill_reg(int spill_reg) { int size = alloc.sizes[spill_reg]; unsigned int spill_offset = last_scratch; assert(ALIGN(spill_offset, 16) == spill_offset); /* oword read/write req. */ /* Spills may use MRFs 13-15 in the SIMD16 case. Our texturing is done * using up to 11 MRFs starting from either m1 or m2, and fb writes can use * up to m13 (gen6+ simd16: 2 header + 8 color + 2 src0alpha + 2 omask) or * m15 (gen4-5 simd16: 2 header + 8 color + 1 aads + 2 src depth + 2 dst * depth), starting from m1. In summary: We may not be able to spill in * SIMD16 mode, because we'd stomp the FB writes. */ if (!spilled_any_registers) { bool mrf_used[BRW_MAX_MRF(devinfo->gen)]; get_used_mrfs(this, mrf_used); for (int i = spill_base_mrf(this); i < BRW_MAX_MRF(devinfo->gen); i++) { if (mrf_used[i]) { fail("Register spilling not supported with m%d used", i); return; } } spilled_any_registers = true; } last_scratch += size * REG_SIZE; /* Generate spill/unspill instructions for the objects being * spilled. Right now, we spill or unspill the whole thing to a * virtual grf of the same size. For most instructions, though, we * could just spill/unspill the GRF being accessed. */ foreach_block_and_inst (block, fs_inst, inst, cfg) { const fs_builder ibld = fs_builder(this, block, inst); for (unsigned int i = 0; i < inst->sources; i++) { if (inst->src[i].file == VGRF && inst->src[i].nr == spill_reg) { int count = regs_read(inst, i); int subset_spill_offset = spill_offset + ROUND_DOWN_TO(inst->src[i].offset, REG_SIZE); fs_reg unspill_dst(VGRF, alloc.allocate(count)); inst->src[i].nr = unspill_dst.nr; inst->src[i].offset %= REG_SIZE; /* We read the largest power-of-two divisor of the register count * (because only POT scratch read blocks are allowed by the * hardware) up to the maximum supported block size. */ const unsigned width = MIN2(32, 1u << (ffs(MAX2(1, count) * 8) - 1)); /* Set exec_all() on unspill messages under the (rather * pessimistic) assumption that there is no one-to-one * correspondence between channels of the spilled variable in * scratch space and the scratch read message, which operates on * 32 bit channels. It shouldn't hurt in any case because the * unspill destination is a block-local temporary. */ emit_unspill(ibld.exec_all().group(width, 0), unspill_dst, subset_spill_offset, count); } } if (inst->dst.file == VGRF && inst->dst.nr == spill_reg) { int subset_spill_offset = spill_offset + ROUND_DOWN_TO(inst->dst.offset, REG_SIZE); fs_reg spill_src(VGRF, alloc.allocate(regs_written(inst))); inst->dst.nr = spill_src.nr; inst->dst.offset %= REG_SIZE; /* If we're immediately spilling the register, we should not use * destination dependency hints. Doing so will cause the GPU do * try to read and write the register at the same time and may * hang the GPU. */ inst->no_dd_clear = false; inst->no_dd_check = false; /* Calculate the execution width of the scratch messages (which work * in terms of 32 bit components so we have a fixed number of eight * channels per spilled register). We attempt to write one * exec_size-wide component of the variable at a time without * exceeding the maximum number of (fake) MRF registers reserved for * spills. */ const unsigned width = 8 * MIN2( DIV_ROUND_UP(inst->dst.component_size(inst->exec_size), REG_SIZE), spill_max_size(this)); /* Spills should only write data initialized by the instruction for * whichever channels are enabled in the excution mask. If that's * not possible we'll have to emit a matching unspill before the * instruction and set force_writemask_all on the spill. */ const bool per_channel = inst->dst.is_contiguous() && type_sz(inst->dst.type) == 4 && inst->exec_size == width; /* Builder used to emit the scratch messages. */ const fs_builder ubld = ibld.exec_all(!per_channel).group(width, 0); /* If our write is going to affect just part of the * regs_written(inst), then we need to unspill the destination since * we write back out all of the regs_written(). If the original * instruction had force_writemask_all set and is not a partial * write, there should be no need for the unspill since the * instruction will be overwriting the whole destination in any case. */ if (inst->is_partial_write() || (!inst->force_writemask_all && !per_channel)) emit_unspill(ubld, spill_src, subset_spill_offset, regs_written(inst)); emit_spill(ubld.at(block, inst->next), spill_src, subset_spill_offset, regs_written(inst)); } } invalidate_live_intervals(); }