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IABSD.fr/xenocara/lib/mesa/src/intel/compiler/brw_lower_simd_width.cpp
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- lib/mesa/src/intel/compiler/brw_lower_simd_width.cpp
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/* * Copyright © 2010 Intel Corporation * SPDX-License-Identifier: MIT */ #include "brw_fs.h" #include "brw_builder.h" using namespace brw; static bool is_mixed_float_with_fp32_dst(const fs_inst *inst) { if (inst->dst.type != BRW_TYPE_F) return false; for (int i = 0; i < inst->sources; i++) { if (inst->src[i].type == BRW_TYPE_HF) return true; } return false; } static bool is_mixed_float_with_packed_fp16_dst(const fs_inst *inst) { if (inst->dst.type != BRW_TYPE_HF || inst->dst.stride != 1) return false; for (int i = 0; i < inst->sources; i++) { if (inst->src[i].type == BRW_TYPE_F) return true; } return false; } /** * Get the closest allowed SIMD width for instruction \p inst accounting for * some common regioning and execution control restrictions that apply to FPU * instructions. These restrictions don't necessarily have any relevance to * instructions not executed by the FPU pipeline like extended math, control * flow or send message instructions. * * For virtual opcodes it's really up to the instruction -- In some cases * (e.g. where a virtual instruction unrolls into a simple sequence of FPU * instructions) it may simplify virtual instruction lowering if we can * enforce FPU-like regioning restrictions already on the virtual instruction, * in other cases (e.g. virtual send-like instructions) this may be * excessively restrictive. */ static unsigned get_fpu_lowered_simd_width(const fs_visitor *shader, const fs_inst *inst) { const struct brw_compiler *compiler = shader->compiler; const struct intel_device_info *devinfo = compiler->devinfo; /* Maximum execution size representable in the instruction controls. */ unsigned max_width = MIN2(32, inst->exec_size); /* Number of channels per polygon handled by a multipolygon PS shader. */ const unsigned poly_width = shader->dispatch_width / MAX2(1, shader->max_polygons); /* Number of registers that will be read by an ATTR source if * present for multipolygon PS shaders, since the PS vertex setup * data for each polygon is stored in different contiguous GRFs. */ const unsigned attr_reg_count = (shader->stage != MESA_SHADER_FRAGMENT || shader->max_polygons < 2 ? 0 : DIV_ROUND_UP(inst->exec_size, poly_width) * reg_unit(devinfo)); /* According to the PRMs: * "A. In Direct Addressing mode, a source cannot span more than 2 * adjacent GRF registers. * B. A destination cannot span more than 2 adjacent GRF registers." * * Look for the source or destination with the largest register region * which is the one that is going to limit the overall execution size of * the instruction due to this rule. */ unsigned reg_count = DIV_ROUND_UP(inst->size_written, REG_SIZE); for (unsigned i = 0; i < inst->sources; i++) reg_count = MAX3(reg_count, DIV_ROUND_UP(inst->size_read(devinfo, i), REG_SIZE), (inst->src[i].file == ATTR ? attr_reg_count : 0)); /* Calculate the maximum execution size of the instruction based on the * factor by which it goes over the hardware limit of 2 GRFs. */ const unsigned max_reg_count = 2 * reg_unit(devinfo); if (reg_count > max_reg_count) max_width = MIN2(max_width, inst->exec_size / DIV_ROUND_UP(reg_count, max_reg_count)); /* From the IVB PRMs (applies to HSW too): * "Instructions with condition modifiers must not use SIMD32." * * From the BDW PRMs (applies to later hardware too): * "Ternary instruction with condition modifiers must not use SIMD32." */ if (inst->conditional_mod && inst->is_3src(compiler) && devinfo->ver < 12) max_width = MIN2(max_width, 16); /* From the IVB PRMs (applies to other devices that don't have the * intel_device_info::supports_simd16_3src flag set): * "In Align16 access mode, SIMD16 is not allowed for DW operations and * SIMD8 is not allowed for DF operations." */ if (inst->is_3src(compiler) && !devinfo->supports_simd16_3src) max_width = MIN2(max_width, inst->exec_size / reg_count); if (inst->opcode != BRW_OPCODE_MOV) { /* From the SKL PRM, Special Restrictions for Handling Mixed Mode * Float Operations: * * "No SIMD16 in mixed mode when destination is f32. Instruction * execution size must be no more than 8." * * Testing indicates that this restriction does not apply to MOVs. */ if (is_mixed_float_with_fp32_dst(inst) && devinfo->ver < 20) max_width = MIN2(max_width, 8); /* From the SKL PRM, Special Restrictions for Handling Mixed Mode * Float Operations: * * "No SIMD16 in mixed mode when destination is packed f16 for both * Align1 and Align16." */ if (is_mixed_float_with_packed_fp16_dst(inst) && devinfo->ver < 20) max_width = MIN2(max_width, 8); } /* Only power-of-two execution sizes are representable in the instruction * control fields. */ return 1 << util_logbase2(max_width); } /** * Get the maximum allowed SIMD width for instruction \p inst accounting for * various payload size restrictions that apply to sampler message * instructions. * * This is only intended to provide a maximum theoretical bound for the * execution size of the message based on the number of argument components * alone, which in most cases will determine whether the SIMD8 or SIMD16 * variant of the message can be used, though some messages may have * additional restrictions not accounted for here (e.g. pre-ILK hardware uses * the message length to determine the exact SIMD width and argument count, * which makes a number of sampler message combinations impossible to * represent). * * Note: Platforms with monolithic SIMD16 double the possible SIMD widths * change from (SIMD8, SIMD16) to (SIMD16, SIMD32). */ static unsigned get_sampler_lowered_simd_width(const struct intel_device_info *devinfo, const fs_inst *inst) { /* If we have a min_lod parameter on anything other than a simple sample * message, it will push it over 5 arguments and we have to fall back to * SIMD8. */ if (inst->opcode != SHADER_OPCODE_TEX_LOGICAL && inst->components_read(TEX_LOGICAL_SRC_MIN_LOD)) return devinfo->ver < 20 ? 8 : 16; /* On Gfx9+ the LOD argument is for free if we're able to use the LZ * variant of the TXL or TXF message. */ const bool implicit_lod = (inst->opcode == SHADER_OPCODE_TXL_LOGICAL || inst->opcode == SHADER_OPCODE_TXF_LOGICAL) && inst->src[TEX_LOGICAL_SRC_LOD].is_zero(); /* Calculate the total number of argument components that need to be passed * to the sampler unit. */ assert(inst->src[TEX_LOGICAL_SRC_GRAD_COMPONENTS].file == IMM); const unsigned grad_components = inst->src[TEX_LOGICAL_SRC_GRAD_COMPONENTS].ud; assert(inst->src[TEX_LOGICAL_SRC_COORD_COMPONENTS].file == IMM); const unsigned coord_components = inst->src[TEX_LOGICAL_SRC_COORD_COMPONENTS].ud; unsigned num_payload_components = coord_components + inst->components_read(TEX_LOGICAL_SRC_SHADOW_C) + (implicit_lod ? 0 : inst->components_read(TEX_LOGICAL_SRC_LOD)) + inst->components_read(TEX_LOGICAL_SRC_LOD2) + inst->components_read(TEX_LOGICAL_SRC_SAMPLE_INDEX) + (inst->opcode == SHADER_OPCODE_TG4_OFFSET_LOGICAL ? inst->components_read(TEX_LOGICAL_SRC_TG4_OFFSET) : 0) + inst->components_read(TEX_LOGICAL_SRC_MCS) + inst->components_read(TEX_LOGICAL_SRC_MIN_LOD); if (inst->opcode == FS_OPCODE_TXB_LOGICAL && devinfo->ver >= 20) { num_payload_components += 3 - coord_components; } else if (inst->opcode == SHADER_OPCODE_TXD_LOGICAL && devinfo->verx10 >= 125 && devinfo->ver < 20) { num_payload_components += 3 - coord_components + (2 - grad_components) * 2; } else { num_payload_components += 4 - coord_components; if (inst->opcode == SHADER_OPCODE_TXD_LOGICAL) num_payload_components += (3 - grad_components) * 2; } const unsigned simd_limit = reg_unit(devinfo) * (num_payload_components > MAX_SAMPLER_MESSAGE_SIZE / 2 ? 8 : 16); /* SIMD16 (SIMD32 on Xe2) messages with more than five arguments exceed the * maximum message size supported by the sampler, regardless of whether a * header is provided or not. */ return MIN2(inst->exec_size, simd_limit); } static bool is_half_float_src_dst(const fs_inst *inst) { if (inst->dst.type == BRW_TYPE_HF) return true; for (int i = 0; i < inst->sources; i++) { if (inst->src[i].type == BRW_TYPE_HF) return true; } return false; } /** * Get the closest native SIMD width supported by the hardware for instruction * \p inst. The instruction will be left untouched by * fs_visitor::lower_simd_width() if the returned value is equal to the * original execution size. */ unsigned brw_get_lowered_simd_width(const fs_visitor *shader, const fs_inst *inst) { const struct brw_compiler *compiler = shader->compiler; const struct intel_device_info *devinfo = compiler->devinfo; switch (inst->opcode) { case BRW_OPCODE_DP4A: case BRW_OPCODE_MOV: case BRW_OPCODE_SEL: case BRW_OPCODE_NOT: case BRW_OPCODE_AND: case BRW_OPCODE_OR: case BRW_OPCODE_XOR: case BRW_OPCODE_SHR: case BRW_OPCODE_SHL: case BRW_OPCODE_ASR: case BRW_OPCODE_ROR: case BRW_OPCODE_ROL: case BRW_OPCODE_CMPN: case BRW_OPCODE_CSEL: case BRW_OPCODE_BFREV: case BRW_OPCODE_BFE: case BRW_OPCODE_ADD: case BRW_OPCODE_MUL: case BRW_OPCODE_AVG: case BRW_OPCODE_FRC: case BRW_OPCODE_RNDU: case BRW_OPCODE_RNDD: case BRW_OPCODE_RNDE: case BRW_OPCODE_RNDZ: case BRW_OPCODE_LZD: case BRW_OPCODE_FBH: case BRW_OPCODE_FBL: case BRW_OPCODE_CBIT: case BRW_OPCODE_MAD: case BRW_OPCODE_LRP: case BRW_OPCODE_ADD3: case FS_OPCODE_PACK: case SHADER_OPCODE_SEL_EXEC: case SHADER_OPCODE_CLUSTER_BROADCAST: case SHADER_OPCODE_MOV_RELOC_IMM: case BRW_OPCODE_CMP: case BRW_OPCODE_BFI1: case BRW_OPCODE_BFI2: return get_fpu_lowered_simd_width(shader, inst); case SHADER_OPCODE_RCP: case SHADER_OPCODE_RSQ: case SHADER_OPCODE_SQRT: case SHADER_OPCODE_EXP2: case SHADER_OPCODE_LOG2: case SHADER_OPCODE_SIN: case SHADER_OPCODE_COS: { /* Xe2+: BSpec 56797 * * Math operation rules when half-floats are used on both source and * destination operands and both source and destinations are packed. * * The execution size must be 16. */ if (is_half_float_src_dst(inst)) return devinfo->ver < 20 ? MIN2(8, inst->exec_size) : MIN2(16, inst->exec_size); if (devinfo->ver < 20) return MIN2(16, inst->exec_size); return inst->exec_size; } case SHADER_OPCODE_POW: { /* SIMD16 is only allowed on Gfx7+. Extended Math Function is limited * to SIMD8 with half-float */ if (is_half_float_src_dst(inst)) return MIN2(8, inst->exec_size); return MIN2(16, inst->exec_size); } case SHADER_OPCODE_USUB_SAT: case SHADER_OPCODE_ISUB_SAT: return get_fpu_lowered_simd_width(shader, inst); case SHADER_OPCODE_INT_QUOTIENT: case SHADER_OPCODE_INT_REMAINDER: /* Integer division is limited to SIMD8 on all generations. */ return MIN2(8, inst->exec_size); case BRW_OPCODE_PLN: case FS_OPCODE_UNIFORM_PULL_CONSTANT_LOAD: case FS_OPCODE_PACK_HALF_2x16_SPLIT: case FS_OPCODE_INTERPOLATE_AT_SAMPLE: case FS_OPCODE_INTERPOLATE_AT_SHARED_OFFSET: case FS_OPCODE_INTERPOLATE_AT_PER_SLOT_OFFSET: case FS_OPCODE_VARYING_PULL_CONSTANT_LOAD_LOGICAL: case FS_OPCODE_DDX_COARSE: case FS_OPCODE_DDX_FINE: case FS_OPCODE_DDY_COARSE: case FS_OPCODE_DDY_FINE: return MIN2(16, inst->exec_size); case SHADER_OPCODE_MULH: /* MULH is lowered to the MUL/MACH sequence using the accumulator, which * is 8-wide on Gfx7+. */ return devinfo->ver >= 20 ? 16 : 8; case FS_OPCODE_FB_WRITE_LOGICAL: if (devinfo->ver >= 20) { /* Dual-source FB writes are unsupported in SIMD32 mode. */ return (inst->src[FB_WRITE_LOGICAL_SRC_COLOR1].file != BAD_FILE ? 16 : MIN2(32, inst->exec_size)); } else { /* Dual-source FB writes are unsupported in SIMD16 mode. */ return (inst->src[FB_WRITE_LOGICAL_SRC_COLOR1].file != BAD_FILE ? 8 : MIN2(16, inst->exec_size)); } case FS_OPCODE_FB_READ_LOGICAL: return MIN2(16, inst->exec_size); case SHADER_OPCODE_TEX_LOGICAL: case SHADER_OPCODE_TXF_MCS_LOGICAL: case SHADER_OPCODE_LOD_LOGICAL: case SHADER_OPCODE_TG4_LOGICAL: case SHADER_OPCODE_SAMPLEINFO_LOGICAL: case SHADER_OPCODE_TXF_CMS_W_LOGICAL: case SHADER_OPCODE_TG4_OFFSET_LOGICAL: case SHADER_OPCODE_TG4_BIAS_LOGICAL: case SHADER_OPCODE_TG4_EXPLICIT_LOD_LOGICAL: case SHADER_OPCODE_TG4_IMPLICIT_LOD_LOGICAL: case SHADER_OPCODE_TG4_OFFSET_LOD_LOGICAL: case SHADER_OPCODE_TG4_OFFSET_BIAS_LOGICAL: case SHADER_OPCODE_TXL_LOGICAL: case FS_OPCODE_TXB_LOGICAL: case SHADER_OPCODE_TXF_LOGICAL: case SHADER_OPCODE_TXS_LOGICAL: return get_sampler_lowered_simd_width(devinfo, inst); case SHADER_OPCODE_MEMORY_LOAD_LOGICAL: case SHADER_OPCODE_MEMORY_STORE_LOGICAL: case SHADER_OPCODE_MEMORY_ATOMIC_LOGICAL: if (devinfo->ver >= 20) return inst->exec_size; if (inst->src[MEMORY_LOGICAL_MODE].ud == MEMORY_MODE_TYPED) return 8; /* HDC A64 atomics are limited to SIMD8 */ if (!devinfo->has_lsc && inst->src[MEMORY_LOGICAL_BINDING_TYPE].ud == LSC_ADDR_SURFTYPE_FLAT && lsc_opcode_is_atomic((enum lsc_opcode) inst->src[MEMORY_LOGICAL_OPCODE].ud)) return 8; return MIN2(16, inst->exec_size); /* On gfx12 parameters are fixed to 16-bit values and therefore they all * always fit regardless of the execution size. */ case SHADER_OPCODE_TXF_CMS_W_GFX12_LOGICAL: return MIN2(16, inst->exec_size); case SHADER_OPCODE_TXD_LOGICAL: /* TXD is unsupported in SIMD16 mode previous to Xe2. SIMD32 is still * unsuppported on Xe2. */ return devinfo->ver < 20 ? 8 : 16; case SHADER_OPCODE_URB_READ_LOGICAL: case SHADER_OPCODE_URB_WRITE_LOGICAL: return MIN2(devinfo->ver < 20 ? 8 : 16, inst->exec_size); case SHADER_OPCODE_QUAD_SWIZZLE: { const unsigned swiz = inst->src[1].ud; return (is_uniform(inst->src[0]) ? get_fpu_lowered_simd_width(shader, inst) : devinfo->ver < 11 && brw_type_size_bytes(inst->src[0].type) == 4 ? 8 : swiz == BRW_SWIZZLE_XYXY || swiz == BRW_SWIZZLE_ZWZW ? 4 : get_fpu_lowered_simd_width(shader, inst)); } case SHADER_OPCODE_MOV_INDIRECT: { /* From IVB and HSW PRMs: * * "2.When the destination requires two registers and the sources are * indirect, the sources must use 1x1 regioning mode. * * In case of DF instructions in HSW/IVB, the exec_size is limited by * the EU decompression logic not handling VxH indirect addressing * correctly. */ const unsigned max_size = 2 * REG_SIZE; /* Prior to Broadwell, we only have 8 address subregisters. */ return MIN3(16, max_size / (inst->dst.stride * brw_type_size_bytes(inst->dst.type)), inst->exec_size); } case SHADER_OPCODE_LOAD_PAYLOAD: { const unsigned reg_count = DIV_ROUND_UP(inst->dst.component_size(inst->exec_size), REG_SIZE * reg_unit(devinfo)); if (reg_count > 2) { /* Only LOAD_PAYLOAD instructions with per-channel destination region * can be easily lowered (which excludes headers and heterogeneous * types). */ assert(!inst->header_size); for (unsigned i = 0; i < inst->sources; i++) assert(brw_type_size_bits(inst->dst.type) == brw_type_size_bits(inst->src[i].type) || inst->src[i].file == BAD_FILE); return inst->exec_size / DIV_ROUND_UP(reg_count, 2); } else { return inst->exec_size; } } default: return inst->exec_size; } } /** * Return true if splitting out the group of channels of instruction \p inst * given by lbld.group() requires allocating a temporary for the i-th source * of the lowered instruction. */ static inline bool needs_src_copy(const brw_builder &lbld, const fs_inst *inst, unsigned i) { /* The indirectly indexed register stays the same even if we split the * instruction. */ if (inst->opcode == SHADER_OPCODE_MOV_INDIRECT && i == 0) return false; return !inst->src[i].is_scalar && (!(is_periodic(inst->src[i], lbld.dispatch_width()) || (inst->components_read(i) == 1 && lbld.dispatch_width() <= inst->exec_size)) || (inst->flags_written(lbld.shader->devinfo) & brw_fs_flag_mask(inst->src[i], brw_type_size_bytes(inst->src[i].type)))); } /** * Extract the data that would be consumed by the channel group given by * lbld.group() from the i-th source region of instruction \p inst and return * it as result in packed form. */ static brw_reg emit_unzip(const brw_builder &lbld, fs_inst *inst, unsigned i) { assert(lbld.group() >= inst->group); /* Specified channel group from the source region. */ const brw_reg src = horiz_offset(inst->src[i], lbld.group() - inst->group); if (needs_src_copy(lbld, inst, i)) { const unsigned num_components = inst->components_read(i); const brw_reg tmp = lbld.vgrf(inst->src[i].type, num_components); assert(num_components <= NIR_MAX_VEC_COMPONENTS); brw_reg comps[NIR_MAX_VEC_COMPONENTS]; for (unsigned k = 0; k < num_components; ++k) comps[k] = offset(src, inst->exec_size, k); lbld.VEC(tmp, comps, num_components); return tmp; } else if (is_periodic(inst->src[i], lbld.dispatch_width()) || (inst->opcode == SHADER_OPCODE_MOV_INDIRECT && i == 0) || inst->src[i].is_scalar) { /* The source is invariant for all dispatch_width-wide groups of the * original region. * * The src[0] of MOV_INDIRECT is invariant regardless of the execution * size. */ return inst->src[i]; } else { /* We can just point the lowered instruction at the right channel group * from the original region. */ return src; } } /** * Return true if splitting out the group of channels of instruction \p inst * given by lbld.group() requires allocating a temporary for the destination * of the lowered instruction and copying the data back to the original * destination region. */ static inline bool needs_dst_copy(const brw_builder &lbld, const fs_inst *inst) { if (inst->dst.is_null()) return false; /* If the instruction writes more than one component we'll have to shuffle * the results of multiple lowered instructions in order to make sure that * they end up arranged correctly in the original destination region. */ if (inst->size_written > inst->dst.component_size(inst->exec_size)) return true; for (unsigned i = 0; i < inst->sources; i++) { /* If we already made a copy of the source for other reasons there won't * be any overlap with the destination. */ if (needs_src_copy(lbld, inst, i)) continue; /* In order to keep the logic simple we emit a copy whenever the * destination region doesn't exactly match an overlapping source, which * may point at the source and destination not being aligned group by * group which could cause one of the lowered instructions to overwrite * the data read from the same source by other lowered instructions. */ if (regions_overlap(inst->dst, inst->size_written, inst->src[i], inst->size_read(lbld.shader->devinfo, i)) && !inst->dst.equals(inst->src[i])) return true; } return false; } /** * Insert data from a packed temporary into the channel group given by * lbld.group() of the destination region of instruction \p inst and return * the temporary as result. Any copy instructions that are required for * unzipping the previous value (in the case of partial writes) will be * inserted using \p lbld_before and any copy instructions required for * zipping up the destination of \p inst will be inserted using \p lbld_after. */ static brw_reg emit_zip(const brw_builder &lbld_before, const brw_builder &lbld_after, fs_inst *inst) { assert(lbld_before.dispatch_width() == lbld_after.dispatch_width()); assert(lbld_before.group() == lbld_after.group()); assert(lbld_after.group() >= inst->group); const struct intel_device_info *devinfo = lbld_before.shader->devinfo; /* Specified channel group from the destination region. */ const brw_reg dst = horiz_offset(inst->dst, lbld_after.group() - inst->group); if (!needs_dst_copy(lbld_after, inst)) { /* No need to allocate a temporary for the lowered instruction, just * take the right group of channels from the original region. */ return dst; } /* Deal with the residency data part later */ const unsigned residency_size = inst->has_sampler_residency() ? (reg_unit(devinfo) * REG_SIZE) : 0; const unsigned dst_size = (inst->size_written - residency_size) / inst->dst.component_size(inst->exec_size); const brw_reg tmp = lbld_after.vgrf(inst->dst.type, dst_size + inst->has_sampler_residency()); if (inst->predicate) { /* Handle predication by copying the original contents of the * destination into the temporary before emitting the lowered * instruction. */ for (unsigned k = 0; k < dst_size; ++k) { lbld_before.MOV(offset(tmp, lbld_before, k), offset(dst, inst->exec_size, k)); } } for (unsigned k = 0; k < dst_size; ++k) { /* Copy the (split) temp into the original (larger) destination */ lbld_after.MOV(offset(dst, inst->exec_size, k), offset(tmp, lbld_after, k)); } if (inst->has_sampler_residency()) { /* Sampler messages with residency need a special attention. In the * first lane of the last component are located the Pixel Null Mask * (bits 0:15) & some upper bits we need to discard (bits 16:31). We * have to build a single 32bit value for the SIMD32 message out of 2 * SIMD16 16 bit values. */ const brw_builder rbld = lbld_after.exec_all().group(1, 0); brw_reg local_res_reg = component( retype(offset(tmp, lbld_before, dst_size), BRW_TYPE_UW), 0); brw_reg final_res_reg = retype(byte_offset(inst->dst, inst->size_written - residency_size + lbld_after.group() / 8), BRW_TYPE_UW); rbld.MOV(final_res_reg, local_res_reg); } return tmp; } bool brw_lower_simd_width(fs_visitor &s) { bool progress = false; foreach_block_and_inst_safe(block, fs_inst, inst, s.cfg) { const unsigned lower_width = brw_get_lowered_simd_width(&s, inst); /* No splitting required */ if (lower_width == inst->exec_size) continue; assert(lower_width < inst->exec_size); /* Builder matching the original instruction. */ const brw_builder bld = brw_builder(&s).at_end(); const brw_builder ibld = bld.at(block, inst).exec_all(inst->force_writemask_all) .group(inst->exec_size, inst->group / inst->exec_size); /* Split the copies in chunks of the execution width of either the * original or the lowered instruction, whichever is lower. */ const unsigned n = DIV_ROUND_UP(inst->exec_size, lower_width); const unsigned residency_size = inst->has_sampler_residency() ? (reg_unit(s.devinfo) * REG_SIZE) : 0; const unsigned dst_size = (inst->size_written - residency_size) / inst->dst.component_size(inst->exec_size); assert(!inst->writes_accumulator && !inst->mlen); /* Inserting the zip, unzip, and duplicated instructions in all of * the right spots is somewhat tricky. All of the unzip and any * instructions from the zip which unzip the destination prior to * writing need to happen before all of the per-group instructions * and the zip instructions need to happen after. In order to sort * this all out, we insert the unzip instructions before \p inst, * insert the per-group instructions after \p inst (i.e. before * inst->next), and insert the zip instructions before the * instruction after \p inst. Since we are inserting instructions * after \p inst, inst->next is a moving target and we need to save * it off here so that we insert the zip instructions in the right * place. * * Since we're inserting split instructions after after_inst, the * instructions will end up in the reverse order that we insert them. * However, certain render target writes require that the low group * instructions come before the high group. From the Ivy Bridge PRM * Vol. 4, Pt. 1, Section 3.9.11: * * "If multiple SIMD8 Dual Source messages are delivered by the * pixel shader thread, each SIMD8_DUALSRC_LO message must be * issued before the SIMD8_DUALSRC_HI message with the same Slot * Group Select setting." * * And, from Section 3.9.11.1 of the same PRM: * * "When SIMD32 or SIMD16 PS threads send render target writes * with multiple SIMD8 and SIMD16 messages, the following must * hold: * * All the slots (as described above) must have a corresponding * render target write irrespective of the slot's validity. A slot * is considered valid when at least one sample is enabled. For * example, a SIMD16 PS thread must send two SIMD8 render target * writes to cover all the slots. * * PS thread must send SIMD render target write messages with * increasing slot numbers. For example, SIMD16 thread has * Slot[15:0] and if two SIMD8 render target writes are used, the * first SIMD8 render target write must send Slot[7:0] and the * next one must send Slot[15:8]." * * In order to make low group instructions come before high group * instructions (this is required for some render target writes), we * split from the highest group to lowest. */ exec_node *const after_inst = inst->next; for (int i = n - 1; i >= 0; i--) { /* Emit a copy of the original instruction with the lowered width. * If the EOT flag was set throw it away except for the last * instruction to avoid killing the thread prematurely. */ fs_inst split_inst = *inst; split_inst.exec_size = lower_width; split_inst.eot = inst->eot && i == int(n - 1); /* Select the correct channel enables for the i-th group, then * transform the sources and destination and emit the lowered * instruction. */ const brw_builder lbld = ibld.group(lower_width, i); for (unsigned j = 0; j < inst->sources; j++) split_inst.src[j] = emit_unzip(lbld.at(block, inst), inst, j); split_inst.dst = emit_zip(lbld.at(block, inst), lbld.at(block, after_inst), inst); split_inst.size_written = split_inst.dst.component_size(lower_width) * dst_size + residency_size; lbld.at(block, inst->next).emit(split_inst); } inst->remove(block); progress = true; } if (progress) s.invalidate_analysis(DEPENDENCY_INSTRUCTIONS | DEPENDENCY_VARIABLES); return progress; }