| /* |
| * Copyright © 2013 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. |
| */ |
| |
| /** @file brw_dead_control_flow.cpp |
| * |
| * This file implements the dead control flow elimination optimization pass. |
| */ |
| |
| #include "brw_shader.h" |
| #include "brw_cfg.h" |
| |
| /* Look for and eliminate dead control flow: |
| * |
| * - if/endif |
| * - else in else/endif |
| * - then in if/else/endif |
| */ |
| bool |
| dead_control_flow_eliminate(backend_shader *s) |
| { |
| bool progress = false; |
| |
| foreach_block_safe (block, s->cfg) { |
| bblock_t *prev_block = block->prev(); |
| |
| if (!prev_block) |
| continue; |
| |
| backend_instruction *const inst = block->start(); |
| backend_instruction *const prev_inst = prev_block->end(); |
| |
| /* ENDIF instructions, by definition, can only be found at the start of |
| * basic blocks. |
| */ |
| if (inst->opcode == BRW_OPCODE_ENDIF && |
| prev_inst->opcode == BRW_OPCODE_ELSE) { |
| bblock_t *const else_block = prev_block; |
| backend_instruction *const else_inst = prev_inst; |
| |
| else_inst->remove(else_block); |
| progress = true; |
| } else if (inst->opcode == BRW_OPCODE_ENDIF && |
| prev_inst->opcode == BRW_OPCODE_IF) { |
| bblock_t *const endif_block = block; |
| bblock_t *const if_block = prev_block; |
| backend_instruction *const endif_inst = inst; |
| backend_instruction *const if_inst = prev_inst; |
| |
| bblock_t *earlier_block = NULL, *later_block = NULL; |
| |
| if (if_block->start_ip == if_block->end_ip) { |
| earlier_block = if_block->prev(); |
| } else { |
| earlier_block = if_block; |
| } |
| if_inst->remove(if_block); |
| |
| if (endif_block->start_ip == endif_block->end_ip) { |
| later_block = endif_block->next(); |
| } else { |
| later_block = endif_block; |
| } |
| endif_inst->remove(endif_block); |
| |
| assert((earlier_block == NULL) == (later_block == NULL)); |
| if (earlier_block && earlier_block->can_combine_with(later_block)) { |
| earlier_block->combine_with(later_block); |
| |
| /* If ENDIF was in its own block, then we've now deleted it and |
| * merged the two surrounding blocks, the latter of which the |
| * __next block pointer was pointing to. |
| */ |
| if (endif_block != later_block) { |
| __next = earlier_block->next(); |
| } |
| } |
| |
| progress = true; |
| } else if (inst->opcode == BRW_OPCODE_ELSE && |
| prev_inst->opcode == BRW_OPCODE_IF) { |
| bblock_t *const else_block = block; |
| backend_instruction *const if_inst = prev_inst; |
| backend_instruction *const else_inst = inst; |
| |
| /* Since the else-branch is becoming the new then-branch, the |
| * condition has to be inverted. |
| */ |
| if_inst->predicate_inverse = !if_inst->predicate_inverse; |
| else_inst->remove(else_block); |
| |
| progress = true; |
| } |
| } |
| |
| if (progress) |
| s->invalidate_live_intervals(); |
| |
| return progress; |
| } |