| /* |
| * 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(!v3d_qpu_writes_flags(&inst->qpu)); |
| 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) |
| 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; |
| } |
| |
| static void |
| vir_dce_flags(struct v3d_compile *c, struct qinst *inst) |
| { |
| if (debug) { |
| fprintf(stderr, |
| "Removing flags write from: "); |
| vir_dump_inst(c, inst); |
| fprintf(stderr, "\n"); |
| } |
| |
| assert(inst->qpu.type == V3D_QPU_INSTR_TYPE_ALU); |
| |
| 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; |
| } |
| |
| static bool |
| check_last_ldunifa(struct v3d_compile *c, |
| struct qinst *inst, |
| struct qblock *block) |
| { |
| if (!inst->qpu.sig.ldunifa && !inst->qpu.sig.ldunifarf) |
| return false; |
| |
| list_for_each_entry_from(struct qinst, scan_inst, inst->link.next, |
| &block->instructions, link) { |
| /* If we find a new write to unifa, then this was the last |
| * ldunifa in its sequence and is safe to remove. |
| */ |
| if (scan_inst->dst.file == QFILE_MAGIC && |
| scan_inst->dst.index == V3D_QPU_WADDR_UNIFA) { |
| return true; |
| } |
| |
| /* If we find another ldunifa in the same sequence then we |
| * can't remove it. |
| */ |
| if (scan_inst->qpu.sig.ldunifa || scan_inst->qpu.sig.ldunifarf) |
| return false; |
| } |
| |
| return true; |
| } |
| |
| static bool |
| check_first_ldunifa(struct v3d_compile *c, |
| struct qinst *inst, |
| struct qblock *block, |
| struct qinst **unifa) |
| { |
| if (!inst->qpu.sig.ldunifa && !inst->qpu.sig.ldunifarf) |
| return false; |
| |
| list_for_each_entry_from_rev(struct qinst, scan_inst, inst->link.prev, |
| &block->instructions, link) { |
| /* If we find a write to unifa, then this was the first |
| * ldunifa in its sequence and is safe to remove. |
| */ |
| if (scan_inst->dst.file == QFILE_MAGIC && |
| scan_inst->dst.index == V3D_QPU_WADDR_UNIFA) { |
| *unifa = scan_inst; |
| return true; |
| } |
| |
| /* If we find another ldunifa in the same sequence then we |
| * can't remove it. |
| */ |
| if (scan_inst->qpu.sig.ldunifa || scan_inst->qpu.sig.ldunifarf) |
| return false; |
| } |
| |
| unreachable("could not find starting unifa for ldunifa sequence"); |
| } |
| |
| static bool |
| increment_unifa_address(struct v3d_compile *c, struct qinst *unifa) |
| { |
| if (unifa->qpu.type == V3D_QPU_INSTR_TYPE_ALU && |
| unifa->qpu.alu.mul.op == V3D_QPU_M_MOV) { |
| c->cursor = vir_after_inst(unifa); |
| struct qreg unifa_reg = vir_reg(QFILE_MAGIC, V3D_QPU_WADDR_UNIFA); |
| vir_ADD_dest(c, unifa_reg, unifa->src[0], vir_uniform_ui(c, 4u)); |
| vir_remove_instruction(c, unifa); |
| return true; |
| } |
| |
| if (unifa->qpu.type == V3D_QPU_INSTR_TYPE_ALU && |
| unifa->qpu.alu.add.op == V3D_QPU_A_ADD) { |
| c->cursor = vir_after_inst(unifa); |
| struct qreg unifa_reg = vir_reg(QFILE_MAGIC, V3D_QPU_WADDR_UNIFA); |
| struct qreg tmp = |
| vir_ADD(c, unifa->src[1], vir_uniform_ui(c, 4u)); |
| vir_ADD_dest(c, unifa_reg, unifa->src[0], tmp); |
| vir_remove_instruction(c, unifa); |
| return true; |
| } |
| |
| return false; |
| } |
| |
| bool |
| vir_opt_dead_code(struct v3d_compile *c) |
| { |
| bool progress = false; |
| bool *used = calloc(c->num_temps, sizeof(bool)); |
| |
| /* Defuse the "are you removing the cursor?" assertion in the core. |
| * You'll need to set up a new cursor for any new instructions after |
| * doing DCE (which we would expect, anyway). |
| */ |
| c->cursor.link = NULL; |
| |
| 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) { |
| struct qinst *last_flags_write = NULL; |
| c->cur_block = block; |
| vir_for_each_inst_safe(inst, block) { |
| /* If this instruction reads the flags, we can't |
| * remove the flags generation for it. |
| */ |
| if (v3d_qpu_reads_flags(&inst->qpu)) |
| last_flags_write = NULL; |
| |
| if (inst->dst.file != QFILE_NULL && |
| !(inst->dst.file == QFILE_TEMP && |
| !used[inst->dst.index])) { |
| continue; |
| } |
| |
| const bool is_ldunifa = inst->qpu.sig.ldunifa || |
| inst->qpu.sig.ldunifarf; |
| |
| if (vir_has_side_effects(c, inst) && !is_ldunifa) |
| continue; |
| |
| bool is_first_ldunifa = false; |
| bool is_last_ldunifa = false; |
| struct qinst *unifa = NULL; |
| if (is_ldunifa) { |
| is_last_ldunifa = |
| check_last_ldunifa(c, inst, block); |
| |
| is_first_ldunifa = |
| check_first_ldunifa(c, inst, block, &unifa); |
| } |
| |
| if (v3d_qpu_writes_flags(&inst->qpu)) { |
| /* If we obscure a previous flags write, |
| * drop it. |
| */ |
| if (last_flags_write && |
| (inst->qpu.flags.apf != V3D_QPU_PF_NONE || |
| inst->qpu.flags.mpf != V3D_QPU_PF_NONE)) { |
| vir_dce_flags(c, last_flags_write); |
| progress = true; |
| } |
| |
| last_flags_write = inst; |
| } |
| |
| if (v3d_qpu_writes_flags(&inst->qpu) || |
| has_nonremovable_reads(c, inst) || |
| (is_ldunifa && !is_first_ldunifa && !is_last_ldunifa)) { |
| /* 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; |
| } |
| |
| /* If we are removing the first ldunifa in a sequence |
| * we need to update the unifa address. |
| */ |
| if (is_first_ldunifa) { |
| assert(unifa); |
| if (!increment_unifa_address(c, unifa)) |
| continue; |
| } |
| |
| assert(inst != last_flags_write); |
| dce(c, inst); |
| progress = true; |
| continue; |
| } |
| } |
| |
| free(used); |
| |
| return progress; |
| } |
