| /* |
| * Copyright © 2014 Broadcom |
| * |
| * 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. |
| */ |
| |
| /** |
| * @file v3d_opt_dead_code.c |
| * |
| * This is a simple dead code eliminator for SSA values in VIR. |
| * |
| * It walks all the instructions finding what temps are used, then walks again |
| * to remove instructions writing unused temps. |
| * |
| * This is an inefficient implementation if you have long chains of |
| * instructions where the entire chain is dead, but we expect those to have |
| * been eliminated at the NIR level, and here we're just cleaning up small |
| * problems produced by NIR->VIR. |
| */ |
| |
| #include "v3d_compiler.h" |
| |
| static bool debug; |
| |
| static void |
| dce(struct v3d_compile *c, struct qinst *inst) |
| { |
| if (debug) { |
| fprintf(stderr, "Removing: "); |
| vir_dump_inst(c, inst); |
| fprintf(stderr, "\n"); |
| } |
| assert(inst->qpu.flags.apf == V3D_QPU_PF_NONE); |
| assert(inst->qpu.flags.mpf == V3D_QPU_PF_NONE); |
| assert(inst->qpu.flags.auf == V3D_QPU_UF_NONE); |
| assert(inst->qpu.flags.muf == V3D_QPU_UF_NONE); |
| vir_remove_instruction(c, inst); |
| } |
| |
| static bool |
| has_nonremovable_reads(struct v3d_compile *c, struct qinst *inst) |
| { |
| for (int i = 0; i < vir_get_nsrc(inst); i++) { |
| if (inst->src[i].file == QFILE_VPM) { |
| /* Instance ID, Vertex ID: Should have been removed at |
| * the NIR level |
| */ |
| if (inst->src[i].index == ~0) |
| return true; |
| |
| uint32_t attr = inst->src[i].index / 4; |
| uint32_t offset = inst->src[i].index % 4; |
| |
| if (c->vattr_sizes[attr] != offset) |
| return true; |
| |
| /* Can't get rid of the last VPM read, or the |
| * simulator (at least) throws an error. |
| */ |
| uint32_t total_size = 0; |
| for (uint32_t i = 0; i < ARRAY_SIZE(c->vattr_sizes); i++) |
| total_size += c->vattr_sizes[i]; |
| if (total_size == 1) |
| return true; |
| } |
| } |
| |
| return false; |
| } |
| |
| static bool |
| can_write_to_null(struct v3d_compile *c, struct qinst *inst) |
| { |
| /* The SFU instructions must write to a physical register. */ |
| if (c->devinfo->ver >= 41 && v3d_qpu_uses_sfu(&inst->qpu)) |
| return false; |
| |
| return true; |
| } |
| |
| bool |
| vir_opt_dead_code(struct v3d_compile *c) |
| { |
| bool progress = false; |
| bool *used = calloc(c->num_temps, sizeof(bool)); |
| |
| vir_for_each_inst_inorder(inst, c) { |
| for (int i = 0; i < vir_get_nsrc(inst); i++) { |
| if (inst->src[i].file == QFILE_TEMP) |
| used[inst->src[i].index] = true; |
| } |
| } |
| |
| vir_for_each_block(block, c) { |
| vir_for_each_inst_safe(inst, block) { |
| if (inst->dst.file != QFILE_NULL && |
| !(inst->dst.file == QFILE_TEMP && |
| !used[inst->dst.index])) { |
| continue; |
| } |
| |
| if (vir_has_side_effects(c, inst)) |
| continue; |
| |
| if (inst->qpu.flags.apf != V3D_QPU_PF_NONE || |
| inst->qpu.flags.mpf != V3D_QPU_PF_NONE || |
| inst->qpu.flags.auf != V3D_QPU_UF_NONE || |
| inst->qpu.flags.muf != V3D_QPU_UF_NONE || |
| has_nonremovable_reads(c, inst)) { |
| /* If we can't remove the instruction, but we |
| * don't need its destination value, just |
| * remove the destination. The register |
| * allocator would trivially color it and it |
| * wouldn't cause any register pressure, but |
| * it's nicer to read the VIR code without |
| * unused destination regs. |
| */ |
| if (inst->dst.file == QFILE_TEMP && |
| can_write_to_null(c, inst)) { |
| if (debug) { |
| fprintf(stderr, |
| "Removing dst from: "); |
| vir_dump_inst(c, inst); |
| fprintf(stderr, "\n"); |
| } |
| c->defs[inst->dst.index] = NULL; |
| inst->dst.file = QFILE_NULL; |
| progress = true; |
| } |
| continue; |
| } |
| |
| for (int i = 0; i < vir_get_nsrc(inst); i++) { |
| if (inst->src[i].file != QFILE_VPM) |
| continue; |
| uint32_t attr = inst->src[i].index / 4; |
| uint32_t offset = (inst->src[i].index % 4); |
| |
| if (c->vattr_sizes[attr] == offset) { |
| c->num_inputs--; |
| c->vattr_sizes[attr]--; |
| } |
| } |
| |
| dce(c, inst); |
| progress = true; |
| continue; |
| } |
| } |
| |
| free(used); |
| |
| return progress; |
| } |