13361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri/* 23361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * Copyright © 2010 Luca Barbieri 33361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * 43361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * Permission is hereby granted, free of charge, to any person obtaining a 53361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * copy of this software and associated documentation files (the "Software"), 63361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * to deal in the Software without restriction, including without limitation 73361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * the rights to use, copy, modify, merge, publish, distribute, sublicense, 83361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * and/or sell copies of the Software, and to permit persons to whom the 93361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * Software is furnished to do so, subject to the following conditions: 103361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * 113361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * The above copyright notice and this permission notice (including the next 123361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * paragraph) shall be included in all copies or substantial portions of the 133361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * Software. 143361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * 153361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 163361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 173361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 183361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 193361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 203361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 213361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * DEALINGS IN THE SOFTWARE. 223361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri */ 233361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 243361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri/** 25df883eb1575a740bf91e01cbe2eaa4dbc1f9f154Chad Versace * \file lower_jumps.cpp 26d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * 27d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * This pass lowers jumps (break, continue, and return) to if/else structures. 28d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * 29d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * It can be asked to: 30d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * 1. Pull jumps out of ifs where possible 31d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * 2. Remove all "continue"s, replacing them with an "execute flag" 32d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * 3. Replace all "break" with a single conditional one at the end of the loop 33d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * 4. Replace all "return"s with a single return at the end of the function, 34d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * for the main function and/or other functions 35d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * 36d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * Applying this pass gives several benefits: 37d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * 1. All functions can be inlined. 38d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * 2. nv40 and other pre-DX10 chips without "continue" can be supported 39d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * 3. nv30 and other pre-DX10 chips with no control flow at all are better 40d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * supported 41d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * 42d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * Continues are lowered by adding a per-loop "execute flag", initialized to 43d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * true, that when cleared inhibits all execution until the end of the loop. 44d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * 45d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * Breaks are lowered to continues, plus setting a "break flag" that is checked 46d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * at the end of the loop, and trigger the unique "break". 47d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * 48d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * Returns are lowered to breaks/continues, plus adding a "return flag" that 49d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * causes loops to break again out of their enclosing loops until all the 50d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * loops are exited: then the "execute flag" logic will ignore everything 51d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * until the end of the function. 52d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * 53d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * Note that "continue" and "return" can also be implemented by adding 54d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * a dummy loop and using break. 55d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * However, this is bad for hardware with limited nesting depth, and 56d2d7a273c51127677d394d1bb9484a2d85c5dcd2Kenneth Graunke * prevents further optimization, and thus is not currently performed. 573361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri */ 583361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 593361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri#include "glsl_types.h" 603361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri#include <string.h> 613361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri#include "ir.h" 623361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 63e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry/** 64e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * Enum recording the result of analyzing how control flow might exit 65e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * an IR node. 66e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * 67e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * Each possible value of jump_strength indicates a strictly stronger 68e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * guarantee on control flow than the previous value. 69e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * 70e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * The ordering of strengths roughly reflects the way jumps are 71e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * lowered: jumps with higher strength tend to be lowered to jumps of 72e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * lower strength. Accordingly, strength is used as a heuristic to 73e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * determine which lowering to perform first. 74e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * 75e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * This enum is also used by get_jump_strength() to categorize 76e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * instructions as either break, continue, return, or other. When 77e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * used in this fashion, strength_always_clears_execute_flag is not 78e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * used. 79e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * 80e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * The control flow analysis made by this optimization pass makes two 81e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * simplifying assumptions: 82e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * 83e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * - It ignores discard instructions, since they are lowered by a 84e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * separate pass (lower_discard.cpp). 85e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * 86e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * - It assumes it is always possible for control to flow from a loop 87e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * to the instruction immediately following it. Technically, this 88e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * is not true (since all execution paths through the loop might 89e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * jump back to the top, or return from the function). 90e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * 91e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * Both of these simplifying assumtions are safe, since they can never 92e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * cause reachable code to be incorrectly classified as unreachable; 93e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * they can only do the opposite. 94e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 953361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbierienum jump_strength 963361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri{ 97e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /** 98e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * Analysis has produced no guarantee on how control flow might 99e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * exit this IR node. It might fall out the bottom (with or 100e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * without clearing the execute flag, if present), or it might 101e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * continue to the top of the innermost enclosing loop, break out 102e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * of it, or return from the function. 103e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 1043361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri strength_none, 105e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry 106e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /** 107e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * The only way control can fall out the bottom of this node is 108e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * through a code path that clears the execute flag. It might also 109e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * continue to the top of the innermost enclosing loop, break out 110e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * of it, or return from the function. 111e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 1123361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri strength_always_clears_execute_flag, 113e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry 114e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /** 115e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * Control cannot fall out the bottom of this node. It might 116e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * continue to the top of the innermost enclosing loop, break out 117e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * of it, or return from the function. 118e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 1193361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri strength_continue, 120e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry 121e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /** 122e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * Control cannot fall out the bottom of this node, or continue the 123e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * top of the innermost enclosing loop. It can only break out of 124e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * it or return from the function. 125e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 1263361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri strength_break, 127e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry 128e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /** 129e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * Control cannot fall out the bottom of this node, continue to the 130e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * top of the innermost enclosing loop, or break out of it. It can 131e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * only return from the function. 132e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 1331b173fb3bad3b53411a4b16a385556b23a247d93Brian Paul strength_return 1343361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri}; 1353361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 1363361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieristruct block_record 1373361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri{ 1383361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri /* minimum jump strength (of lowered IR, not pre-lowering IR) 1393361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * 1403361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * If the block ends with a jump, must be the strength of the jump. 1413361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * Otherwise, the jump would be dead and have been deleted before) 1423361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * 1433361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * If the block doesn't end with a jump, it can be different than strength_none if all paths before it lead to some jump 1443361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * (e.g. an if with a return in one branch, and a break in the other, while not lowering them) 1453361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * Note that identical jumps are usually unified though. 1463361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri */ 1473361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri jump_strength min_strength; 1483361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 1493361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri /* can anything clear the execute flag? */ 1503361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri bool may_clear_execute_flag; 1513361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 1523361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri block_record() 1533361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri { 1543361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->min_strength = strength_none; 1553361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->may_clear_execute_flag = false; 1563361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 1573361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri}; 1583361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 1593361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieristruct loop_record 1603361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri{ 1613361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_function_signature* signature; 1623361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_loop* loop; 1633361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 1643361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri /* used to avoid lowering the break used to represent lowered breaks */ 1653361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri unsigned nesting_depth; 1663361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri bool in_if_at_the_end_of_the_loop; 1673361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 1683361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri bool may_set_return_flag; 1693361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 1703361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_variable* break_flag; 1713361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_variable* execute_flag; /* cleared to emulate continue */ 1723361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 1733361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri loop_record(ir_function_signature* p_signature = 0, ir_loop* p_loop = 0) 1743361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri { 1753361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->signature = p_signature; 1763361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->loop = p_loop; 1773361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->nesting_depth = 0; 1783361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->in_if_at_the_end_of_the_loop = false; 1793361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->may_set_return_flag = false; 1803361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->break_flag = 0; 1813361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->execute_flag = 0; 1823361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 1833361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 1843361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_variable* get_execute_flag() 1853361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri { 1863361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri /* also supported for the "function loop" */ 1873361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(!this->execute_flag) { 1883361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri exec_list& list = this->loop ? this->loop->body_instructions : signature->body; 1893361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->execute_flag = new(this->signature) ir_variable(glsl_type::bool_type, "execute_flag", ir_var_temporary); 1903361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri list.push_head(new(this->signature) ir_assignment(new(this->signature) ir_dereference_variable(execute_flag), new(this->signature) ir_constant(true), 0)); 1913361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri list.push_head(this->execute_flag); 1923361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 1933361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri return this->execute_flag; 1943361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 1953361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 1963361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_variable* get_break_flag() 1973361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri { 1983361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri assert(this->loop); 1993361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(!this->break_flag) { 2003361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->break_flag = new(this->signature) ir_variable(glsl_type::bool_type, "break_flag", ir_var_temporary); 2013361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->loop->insert_before(this->break_flag); 2023361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->loop->insert_before(new(this->signature) ir_assignment(new(this->signature) ir_dereference_variable(break_flag), new(this->signature) ir_constant(false), 0)); 2033361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 2043361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri return this->break_flag; 2053361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 2063361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri}; 2073361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 2083361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieristruct function_record 2093361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri{ 2103361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_function_signature* signature; 2113361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_variable* return_flag; /* used to break out of all loops and then jump to the return instruction */ 2123361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_variable* return_value; 213dbaa2e627effbe1361e1a69c23cf247cf86f2709Paul Berry bool lower_return; 2143361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri unsigned nesting_depth; 2153361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 216dbaa2e627effbe1361e1a69c23cf247cf86f2709Paul Berry function_record(ir_function_signature* p_signature = 0, 217dbaa2e627effbe1361e1a69c23cf247cf86f2709Paul Berry bool lower_return = false) 2183361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri { 2193361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->signature = p_signature; 2203361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->return_flag = 0; 2213361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->return_value = 0; 2223361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->nesting_depth = 0; 223dbaa2e627effbe1361e1a69c23cf247cf86f2709Paul Berry this->lower_return = lower_return; 2243361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 2253361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 2263361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_variable* get_return_flag() 2273361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri { 2283361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(!this->return_flag) { 2293361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->return_flag = new(this->signature) ir_variable(glsl_type::bool_type, "return_flag", ir_var_temporary); 2303361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->signature->body.push_head(new(this->signature) ir_assignment(new(this->signature) ir_dereference_variable(return_flag), new(this->signature) ir_constant(false), 0)); 2313361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->signature->body.push_head(this->return_flag); 2323361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 2333361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri return this->return_flag; 2343361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 2353361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 2363361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_variable* get_return_value() 2373361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri { 2383361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(!this->return_value) { 2393361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri assert(!this->signature->return_type->is_void()); 2403361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri return_value = new(this->signature) ir_variable(this->signature->return_type, "return_value", ir_var_temporary); 2413361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->signature->body.push_head(this->return_value); 2423361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 2433361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri return this->return_value; 2443361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 2453361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri}; 2463361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 2473361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieristruct ir_lower_jumps_visitor : public ir_control_flow_visitor { 248e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* Postconditions: on exit of any visit() function: 249e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * 250e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * ANALYSIS: this->block.min_strength, 251e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * this->block.may_clear_execute_flag, and 252e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * this->loop.may_set_return_flag are updated to reflect the 253e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * characteristics of the visited statement. 254e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * 255e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * DEAD_CODE_ELIMINATION: If this->block.min_strength is not 256e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * strength_none, the visited node is at the end of its exec_list. 257e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * In other words, any unreachable statements that follow the 258e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * visited statement in its exec_list have been removed. 259e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * 260e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * CONTAINED_JUMPS_LOWERED: If the visited statement contains other 261e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * statements, then should_lower_jump() is false for all of the 262e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * return, break, or continue statements it contains. 263e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * 264e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * Note that visiting a jump does not lower it. That is the 265e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * responsibility of the statement (or function signature) that 266e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * contains the jump. 267e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 268e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry 2693361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri bool progress; 2703361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 2713361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri struct function_record function; 2723361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri struct loop_record loop; 2733361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri struct block_record block; 2743361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 2753361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri bool pull_out_jumps; 2763361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri bool lower_continue; 2773361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri bool lower_break; 2783361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri bool lower_sub_return; 2793361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri bool lower_main_return; 2803361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 2813361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_lower_jumps_visitor() 2823361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri { 2833361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->progress = false; 2843361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 2853361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 2863361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri void truncate_after_instruction(exec_node *ir) 2873361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri { 2883361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if (!ir) 2893361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri return; 2903361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 2913361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri while (!ir->get_next()->is_tail_sentinel()) { 2923361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ((ir_instruction *)ir->get_next())->remove(); 2933361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->progress = true; 2943361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 2953361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 2963361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 2973361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri void move_outer_block_inside(ir_instruction *ir, exec_list *inner_block) 2983361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri { 2993361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri while (!ir->get_next()->is_tail_sentinel()) { 3003361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_instruction *move_ir = (ir_instruction *)ir->get_next(); 3013361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 3023361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri move_ir->remove(); 3033361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri inner_block->push_tail(move_ir); 3043361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 3053361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 3063361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 30703145ba655ad9173a74b853843eccaae78ff392fPaul Berry /** 30803145ba655ad9173a74b853843eccaae78ff392fPaul Berry * Insert the instructions necessary to lower a return statement, 30903145ba655ad9173a74b853843eccaae78ff392fPaul Berry * before the given return instruction. 31003145ba655ad9173a74b853843eccaae78ff392fPaul Berry */ 31103145ba655ad9173a74b853843eccaae78ff392fPaul Berry void insert_lowered_return(ir_return *ir) 31203145ba655ad9173a74b853843eccaae78ff392fPaul Berry { 31303145ba655ad9173a74b853843eccaae78ff392fPaul Berry ir_variable* return_flag = this->function.get_return_flag(); 31403145ba655ad9173a74b853843eccaae78ff392fPaul Berry if(!this->function.signature->return_type->is_void()) { 31503145ba655ad9173a74b853843eccaae78ff392fPaul Berry ir_variable* return_value = this->function.get_return_value(); 31603145ba655ad9173a74b853843eccaae78ff392fPaul Berry ir->insert_before( 31703145ba655ad9173a74b853843eccaae78ff392fPaul Berry new(ir) ir_assignment( 31803145ba655ad9173a74b853843eccaae78ff392fPaul Berry new (ir) ir_dereference_variable(return_value), 31903145ba655ad9173a74b853843eccaae78ff392fPaul Berry ir->value)); 32003145ba655ad9173a74b853843eccaae78ff392fPaul Berry } 32103145ba655ad9173a74b853843eccaae78ff392fPaul Berry ir->insert_before( 32203145ba655ad9173a74b853843eccaae78ff392fPaul Berry new(ir) ir_assignment( 32303145ba655ad9173a74b853843eccaae78ff392fPaul Berry new (ir) ir_dereference_variable(return_flag), 32403145ba655ad9173a74b853843eccaae78ff392fPaul Berry new (ir) ir_constant(true))); 32503145ba655ad9173a74b853843eccaae78ff392fPaul Berry this->loop.may_set_return_flag = true; 32603145ba655ad9173a74b853843eccaae78ff392fPaul Berry } 32703145ba655ad9173a74b853843eccaae78ff392fPaul Berry 32803145ba655ad9173a74b853843eccaae78ff392fPaul Berry /** 32903145ba655ad9173a74b853843eccaae78ff392fPaul Berry * If the given instruction is a return, lower it to instructions 33003145ba655ad9173a74b853843eccaae78ff392fPaul Berry * that store the return value (if there is one), set the return 33103145ba655ad9173a74b853843eccaae78ff392fPaul Berry * flag, and then break. 33203145ba655ad9173a74b853843eccaae78ff392fPaul Berry * 33303145ba655ad9173a74b853843eccaae78ff392fPaul Berry * It is safe to pass NULL to this function. 33403145ba655ad9173a74b853843eccaae78ff392fPaul Berry */ 33503145ba655ad9173a74b853843eccaae78ff392fPaul Berry void lower_return_unconditionally(ir_instruction *ir) 33603145ba655ad9173a74b853843eccaae78ff392fPaul Berry { 33703145ba655ad9173a74b853843eccaae78ff392fPaul Berry if (get_jump_strength(ir) != strength_return) { 33803145ba655ad9173a74b853843eccaae78ff392fPaul Berry return; 33903145ba655ad9173a74b853843eccaae78ff392fPaul Berry } 34003145ba655ad9173a74b853843eccaae78ff392fPaul Berry insert_lowered_return((ir_return*)ir); 34103145ba655ad9173a74b853843eccaae78ff392fPaul Berry ir->replace_with(new(ir) ir_loop_jump(ir_loop_jump::jump_break)); 34203145ba655ad9173a74b853843eccaae78ff392fPaul Berry } 34303145ba655ad9173a74b853843eccaae78ff392fPaul Berry 344067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry /** 345067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry * Create the necessary instruction to replace a break instruction. 346067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry */ 347067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry ir_instruction *create_lowered_break() 348067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry { 349067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry void *ctx = this->function.signature; 350067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry return new(ctx) ir_assignment( 351067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry new(ctx) ir_dereference_variable(this->loop.get_break_flag()), 352067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry new(ctx) ir_constant(true), 353067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry 0); 354067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry } 355067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry 356067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry /** 357067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry * If the given instruction is a break, lower it to an instruction 358067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry * that sets the break flag, without consulting 359067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry * should_lower_jump(). 360067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry * 361067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry * It is safe to pass NULL to this function. 362067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry */ 363067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry void lower_break_unconditionally(ir_instruction *ir) 364067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry { 365067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry if (get_jump_strength(ir) != strength_break) { 366067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry return; 367067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry } 368067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry ir->replace_with(create_lowered_break()); 369067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry } 370067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry 371067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry /** 372067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry * If the block ends in a conditional or unconditional break, lower 373067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry * it, even though should_lower_jump() says it needn't be lowered. 374067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry */ 375067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry void lower_final_breaks(exec_list *block) 376067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry { 377067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry ir_instruction *ir = (ir_instruction *) block->get_tail(); 378067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry lower_break_unconditionally(ir); 379067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry ir_if *ir_if = ir->as_if(); 380067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry if (ir_if) { 381067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry lower_break_unconditionally( 382067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry (ir_instruction *) ir_if->then_instructions.get_tail()); 383067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry lower_break_unconditionally( 384067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry (ir_instruction *) ir_if->else_instructions.get_tail()); 385067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry } 386067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry } 387067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry 3883361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri virtual void visit(class ir_loop_jump * ir) 3893361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri { 390e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* Eliminate all instructions after each one, since they are 391e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * unreachable. This satisfies the DEAD_CODE_ELIMINATION 392e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * postcondition. 393e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 3943361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri truncate_after_instruction(ir); 395e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry 396e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* Set this->block.min_strength based on this instruction. This 397e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * satisfies the ANALYSIS postcondition. It is not necessary to 398e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * update this->block.may_clear_execute_flag or 399e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * this->loop.may_set_return_flag, because an unlowered jump 400e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * instruction can't change any flags. 401e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 4023361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->block.min_strength = ir->is_break() ? strength_break : strength_continue; 403e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry 404e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* The CONTAINED_JUMPS_LOWERED postcondition is already 405e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * satisfied, because jump statements can't contain other 406e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * statements. 407e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 4083361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 4093361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 4103361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri virtual void visit(class ir_return * ir) 4113361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri { 412e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* Eliminate all instructions after each one, since they are 413e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * unreachable. This satisfies the DEAD_CODE_ELIMINATION 414e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * postcondition. 415e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 4163361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri truncate_after_instruction(ir); 417e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry 418e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* Set this->block.min_strength based on this instruction. This 419e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * satisfies the ANALYSIS postcondition. It is not necessary to 420e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * update this->block.may_clear_execute_flag or 421e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * this->loop.may_set_return_flag, because an unlowered return 422e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * instruction can't change any flags. 423e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 4243361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->block.min_strength = strength_return; 425e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry 426e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* The CONTAINED_JUMPS_LOWERED postcondition is already 427e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * satisfied, because jump statements can't contain other 428e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * statements. 429e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 4303361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 4313361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 4323361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri virtual void visit(class ir_discard * ir) 4333361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri { 434e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* Nothing needs to be done. The ANALYSIS and 435e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * DEAD_CODE_ELIMINATION postconditions are already satisfied, 436e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * because discard statements are ignored by this optimization 437e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * pass. The CONTAINED_JUMPS_LOWERED postcondition is already 438e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * satisfied, because discard statements can't contain other 439e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * statements. 440e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 4419a3bd5e0452c9c791ba94155d3c9ddba42abd114Ian Romanick (void) ir; 4423361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 4433361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 4443361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri enum jump_strength get_jump_strength(ir_instruction* ir) 4453361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri { 4463361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(!ir) 4473361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri return strength_none; 4483361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri else if(ir->ir_type == ir_type_loop_jump) { 4493361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(((ir_loop_jump*)ir)->is_break()) 4503361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri return strength_break; 4513361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri else 4523361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri return strength_continue; 4533361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } else if(ir->ir_type == ir_type_return) 4543361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri return strength_return; 4553361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri else 4563361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri return strength_none; 4573361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 4583361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 4593361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri bool should_lower_jump(ir_jump* ir) 4603361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri { 4613361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri unsigned strength = get_jump_strength(ir); 4623361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri bool lower; 4633361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri switch(strength) 4643361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri { 4653361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri case strength_none: 4663361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri lower = false; /* don't change this, code relies on it */ 4673361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri break; 4683361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri case strength_continue: 4693361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri lower = lower_continue; 4703361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri break; 4713361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri case strength_break: 4723361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri assert(this->loop.loop); 4733361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri /* never lower "canonical break" */ 4743361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(ir->get_next()->is_tail_sentinel() && (this->loop.nesting_depth == 0 4753361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri || (this->loop.nesting_depth == 1 && this->loop.in_if_at_the_end_of_the_loop))) 4763361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri lower = false; 4773361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri else 4783361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri lower = lower_break; 4793361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri break; 4803361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri case strength_return: 4813361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri /* never lower return at the end of a this->function */ 4823361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(this->function.nesting_depth == 0 && ir->get_next()->is_tail_sentinel()) 4833361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri lower = false; 4843361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri else 485dbaa2e627effbe1361e1a69c23cf247cf86f2709Paul Berry lower = this->function.lower_return; 4863361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri break; 4873361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 4883361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri return lower; 4893361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 4903361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 4913361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri block_record visit_block(exec_list* list) 4923361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri { 493382cee91a4bbbee45897239e6802ccaa5a5ad9c3Paul Berry /* Note: since visiting a node may change that node's next 494382cee91a4bbbee45897239e6802ccaa5a5ad9c3Paul Berry * pointer, we can't use visit_exec_list(), because 495382cee91a4bbbee45897239e6802ccaa5a5ad9c3Paul Berry * visit_exec_list() caches the node's next pointer before 496382cee91a4bbbee45897239e6802ccaa5a5ad9c3Paul Berry * visiting it. So we use foreach_list() instead. 497382cee91a4bbbee45897239e6802ccaa5a5ad9c3Paul Berry * 498382cee91a4bbbee45897239e6802ccaa5a5ad9c3Paul Berry * foreach_list() isn't safe if the node being visited gets 499382cee91a4bbbee45897239e6802ccaa5a5ad9c3Paul Berry * removed, but fortunately this visitor doesn't do that. 500382cee91a4bbbee45897239e6802ccaa5a5ad9c3Paul Berry */ 501382cee91a4bbbee45897239e6802ccaa5a5ad9c3Paul Berry 5023361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri block_record saved_block = this->block; 5033361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->block = block_record(); 504382cee91a4bbbee45897239e6802ccaa5a5ad9c3Paul Berry foreach_list(node, list) { 505382cee91a4bbbee45897239e6802ccaa5a5ad9c3Paul Berry ((ir_instruction *) node)->accept(this); 506382cee91a4bbbee45897239e6802ccaa5a5ad9c3Paul Berry } 5073361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri block_record ret = this->block; 5083361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->block = saved_block; 5093361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri return ret; 5103361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 5113361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 5123361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri virtual void visit(ir_if *ir) 5133361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri { 5143361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(this->loop.nesting_depth == 0 && ir->get_next()->is_tail_sentinel()) 5153361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->loop.in_if_at_the_end_of_the_loop = true; 5163361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 5173361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ++this->function.nesting_depth; 5183361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ++this->loop.nesting_depth; 5193361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 5203361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri block_record block_records[2]; 5213361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_jump* jumps[2]; 5223361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 523e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* Recursively lower nested jumps. This satisfies the 524e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * CONTAINED_JUMPS_LOWERED postcondition, except in the case of 525e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * unconditional jumps at the end of ir->then_instructions and 526e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * ir->else_instructions, which are handled below. 527e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 5283361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri block_records[0] = visit_block(&ir->then_instructions); 5293361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri block_records[1] = visit_block(&ir->else_instructions); 5303361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 5313361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieriretry: /* we get here if we put code after the if inside a branch */ 5323361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 533e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* Determine which of ir->then_instructions and 534e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * ir->else_instructions end with an unconditional jump. 535e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 536e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry for(unsigned i = 0; i < 2; ++i) { 537e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry exec_list& list = i ? ir->else_instructions : ir->then_instructions; 538e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry jumps[i] = 0; 539e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry if(!list.is_empty() && get_jump_strength((ir_instruction*)list.get_tail())) 540e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry jumps[i] = (ir_jump*)list.get_tail(); 541e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry } 542e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry 543e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* Loop until we have satisfied the CONTAINED_JUMPS_LOWERED 544e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * postcondition by lowering jumps in both then_instructions and 545e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * else_instructions. 546e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 5473361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri for(;;) { 548e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* Determine the types of the jumps that terminate 549e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * ir->then_instructions and ir->else_instructions. 550e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 5513361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri jump_strength jump_strengths[2]; 5523361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 5533361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri for(unsigned i = 0; i < 2; ++i) { 5543361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(jumps[i]) { 5553361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri jump_strengths[i] = block_records[i].min_strength; 5563361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri assert(jump_strengths[i] == get_jump_strength(jumps[i])); 5573361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } else 5583361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri jump_strengths[i] = strength_none; 5593361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 5603361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 561e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* If both code paths end in a jump, and the jumps are the 562e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * same, and we are pulling out jumps, replace them with a 563e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * single jump that comes after the if instruction. The new 564e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * jump will be visited next, and it will be lowered if 565e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * necessary by the loop or conditional that encloses it. 566e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 5673361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(pull_out_jumps && jump_strengths[0] == jump_strengths[1]) { 5683361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri bool unify = true; 5693361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(jump_strengths[0] == strength_continue) 5703361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir->insert_after(new(ir) ir_loop_jump(ir_loop_jump::jump_continue)); 5713361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri else if(jump_strengths[0] == strength_break) 5723361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir->insert_after(new(ir) ir_loop_jump(ir_loop_jump::jump_break)); 5733361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri /* FINISHME: unify returns with identical expressions */ 5743361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri else if(jump_strengths[0] == strength_return && this->function.signature->return_type->is_void()) 5753361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir->insert_after(new(ir) ir_return(NULL)); 5761802cb9bafc4125300870be51e8b22ddd795d61eKenneth Graunke else 5771802cb9bafc4125300870be51e8b22ddd795d61eKenneth Graunke unify = false; 5783361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 5793361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(unify) { 5803361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri jumps[0]->remove(); 5813361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri jumps[1]->remove(); 5823361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->progress = true; 5833361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 584e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* Update jumps[] to reflect the fact that the jumps 585e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * are gone, and update block_records[] to reflect the 586e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * fact that control can now flow to the next 587e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * instruction. 588e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 5893361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri jumps[0] = 0; 5903361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri jumps[1] = 0; 5913361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri block_records[0].min_strength = strength_none; 5923361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri block_records[1].min_strength = strength_none; 593e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry 594e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* The CONTAINED_JUMPS_LOWERED postcondition is now 595e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * satisfied, so we can break out of the loop. 596e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 5973361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri break; 5983361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 5993361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 6003361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 6013361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri /* lower a jump: if both need to lowered, start with the strongest one, so that 6023361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * we might later unify the lowered version with the other one 6033361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri */ 6043361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri bool should_lower[2]; 6053361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri for(unsigned i = 0; i < 2; ++i) 6063361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri should_lower[i] = should_lower_jump(jumps[i]); 6073361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 6083361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri int lower; 6093361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(should_lower[1] && should_lower[0]) 6103361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri lower = jump_strengths[1] > jump_strengths[0]; 6113361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri else if(should_lower[0]) 6123361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri lower = 0; 6133361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri else if(should_lower[1]) 6143361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri lower = 1; 6153361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri else 616e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* Neither code path ends in a jump that needs to be 617e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * lowered, so the CONTAINED_JUMPS_LOWERED postcondition 618e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * is satisfied and we can break out of the loop. 619e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 6203361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri break; 6213361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 6223361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(jump_strengths[lower] == strength_return) { 623e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* To lower a return, we create a return flag (if the 624e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * function doesn't have one already) and add instructions 625e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * that: 1. store the return value (if this function has a 626e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * non-void return) and 2. set the return flag 627e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 62803145ba655ad9173a74b853843eccaae78ff392fPaul Berry insert_lowered_return((ir_return*)jumps[lower]); 6293361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(this->loop.loop) { 630e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* If we are in a loop, replace the return instruction 631e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * with a break instruction, and then loop so that the 632e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * break instruction can be lowered if necessary. 633e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 6343361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_loop_jump* lowered = 0; 6353361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri lowered = new(ir) ir_loop_jump(ir_loop_jump::jump_break); 636e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* Note: we must update block_records and jumps to 637e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * reflect the fact that the control path has been 638e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * altered from a return to a break. 639e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 6403361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri block_records[lower].min_strength = strength_break; 6413361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri jumps[lower]->replace_with(lowered); 6423361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri jumps[lower] = lowered; 643e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry } else { 644e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* If we are not in a loop, we then proceed as we would 645e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * for a continue statement (set the execute flag to 646e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * false to prevent the rest of the function from 647e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * executing). 648e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 6493361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri goto lower_continue; 650e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry } 6513361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->progress = true; 6523361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } else if(jump_strengths[lower] == strength_break) { 653e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* To lower a break, we create a break flag (if the loop 654e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * doesn't have one already) and add an instruction that 655e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * sets it. 6563361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * 657e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * Then we proceed as we would for a continue statement 658e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * (set the execute flag to false to prevent the rest of 659e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * the loop body from executing). 6603361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri * 661e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * The visit() function for the loop will ensure that the 662e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * break flag is checked after executing the loop body. 6633361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri */ 664067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry jumps[lower]->insert_before(create_lowered_break()); 6653361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri goto lower_continue; 6663361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } else if(jump_strengths[lower] == strength_continue) { 6673361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbierilower_continue: 668e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* To lower a continue, we create an execute flag (if the 669e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * loop doesn't have one already) and replace the continue 670e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * with an instruction that clears it. 671e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * 672e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * Note that this code path gets exercised when lowering 673e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * return statements that are not inside a loop, so 674e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * this->loop must be initialized even outside of loops. 675e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 6763361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_variable* execute_flag = this->loop.get_execute_flag(); 6773361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri jumps[lower]->replace_with(new(ir) ir_assignment(new (ir) ir_dereference_variable(execute_flag), new (ir) ir_constant(false), 0)); 678e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* Note: we must update block_records and jumps to reflect 679e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * the fact that the control path has been altered to an 680e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * instruction that clears the execute flag. 681e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 6823361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri jumps[lower] = 0; 6833361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri block_records[lower].min_strength = strength_always_clears_execute_flag; 6843361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri block_records[lower].may_clear_execute_flag = true; 6853361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->progress = true; 686e71b4ab8a64bf978b2036976a41e30996eebb0c8Paul Berry 687e71b4ab8a64bf978b2036976a41e30996eebb0c8Paul Berry /* Let the loop run again, in case the other branch of the 688e71b4ab8a64bf978b2036976a41e30996eebb0c8Paul Berry * if needs to be lowered too. 689e71b4ab8a64bf978b2036976a41e30996eebb0c8Paul Berry */ 6903361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 6913361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 6923361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 6933361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri /* move out a jump out if possible */ 6943361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(pull_out_jumps) { 695e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* If one of the branches ends in a jump, and control cannot 696e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * fall out the bottom of the other branch, then we can move 697e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * the jump after the if. 698e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * 699e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * Set move_out to the branch we are moving a jump out of. 700e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 7013361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri int move_out = -1; 7023361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(jumps[0] && block_records[1].min_strength >= strength_continue) 7033361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri move_out = 0; 7043361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri else if(jumps[1] && block_records[0].min_strength >= strength_continue) 7053361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri move_out = 1; 7063361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 7073361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(move_out >= 0) 7083361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri { 7093361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri jumps[move_out]->remove(); 7103361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir->insert_after(jumps[move_out]); 711e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* Note: we must update block_records and jumps to reflect 712e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * the fact that the jump has been moved out of the if. 713e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 7143361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri jumps[move_out] = 0; 7153361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri block_records[move_out].min_strength = strength_none; 7163361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->progress = true; 7173361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 7183361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 7193361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 720e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* Now satisfy the ANALYSIS postcondition by setting 721e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * this->block.min_strength and 722e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * this->block.may_clear_execute_flag based on the 723e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * characteristics of the two branches. 724e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 7253361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(block_records[0].min_strength < block_records[1].min_strength) 7263361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->block.min_strength = block_records[0].min_strength; 7273361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri else 7283361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->block.min_strength = block_records[1].min_strength; 7293361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->block.may_clear_execute_flag = this->block.may_clear_execute_flag || block_records[0].may_clear_execute_flag || block_records[1].may_clear_execute_flag; 7303361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 731e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* Now we need to clean up the instructions that follow the 732e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * if. 733e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * 734e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * If those instructions are unreachable, then satisfy the 735e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * DEAD_CODE_ELIMINATION postcondition by eliminating them. 736e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * Otherwise that postcondition is already satisfied. 737e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 7383361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(this->block.min_strength) 7393361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri truncate_after_instruction(ir); 7403361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri else if(this->block.may_clear_execute_flag) 7413361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri { 742e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* If the "if" instruction might clear the execute flag, then 743e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * we need to guard any instructions that follow so that they 744e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * are only executed if the execute flag is set. 745e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * 746e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * If one of the branches of the "if" always clears the 747e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * execute flag, and the other branch never clears it, then 748e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * this is easy: just move all the instructions following the 749e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * "if" into the branch that never clears it. 750e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 7513361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri int move_into = -1; 7523361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(block_records[0].min_strength && !block_records[1].may_clear_execute_flag) 7533361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri move_into = 1; 7543361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri else if(block_records[1].min_strength && !block_records[0].may_clear_execute_flag) 7553361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri move_into = 0; 7563361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 7573361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(move_into >= 0) { 7583361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri assert(!block_records[move_into].min_strength && !block_records[move_into].may_clear_execute_flag); /* otherwise, we just truncated */ 7593361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 7603361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri exec_list* list = move_into ? &ir->else_instructions : &ir->then_instructions; 7613361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri exec_node* next = ir->get_next(); 7623361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(!next->is_tail_sentinel()) { 7633361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri move_outer_block_inside(ir, list); 7643361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 765e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* If any instructions moved, then we need to visit 766e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * them (since they are now inside the "if"). Since 767e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * block_records[move_into] is in its default state 768e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * (see assertion above), we can safely replace 769e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * block_records[move_into] with the result of this 770e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * analysis. 771e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 7723361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri exec_list list; 7733361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri list.head = next; 7743361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri block_records[move_into] = visit_block(&list); 7753361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 776e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* 777e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * Then we need to re-start our jump lowering, since one 778e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * of the instructions we moved might be a jump that 779e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * needs to be lowered. 780e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 7813361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->progress = true; 7823361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri goto retry; 7833361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 7843361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } else { 785e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* If we get here, then the simple case didn't apply; we 786e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * need to actually guard the instructions that follow. 787e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * 788e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * To avoid creating unnecessarily-deep nesting, first 789e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * look through the instructions that follow and unwrap 790e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * any instructions that that are already wrapped in the 791e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * appropriate guard. 792e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 7933361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_instruction* ir_after; 7943361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri for(ir_after = (ir_instruction*)ir->get_next(); !ir_after->is_tail_sentinel();) 7953361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri { 7963361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_if* ir_if = ir_after->as_if(); 7973361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(ir_if && ir_if->else_instructions.is_empty()) { 7983361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_dereference_variable* ir_if_cond_deref = ir_if->condition->as_dereference_variable(); 7993361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(ir_if_cond_deref && ir_if_cond_deref->var == this->loop.execute_flag) { 8003361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_instruction* ir_next = (ir_instruction*)ir_after->get_next(); 8013361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_after->insert_before(&ir_if->then_instructions); 8023361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_after->remove(); 8033361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_after = ir_next; 8043361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri continue; 8053361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 8063361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 8073361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_after = (ir_instruction*)ir_after->get_next(); 8083361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 8093361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri /* only set this if we find any unprotected instruction */ 8103361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->progress = true; 8113361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 8123361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 813e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* Then, wrap all the instructions that follow in a single 814e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * guard. 815e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 8163361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(!ir->get_next()->is_tail_sentinel()) { 8173361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri assert(this->loop.execute_flag); 8183361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_if* if_execute = new(ir) ir_if(new(ir) ir_dereference_variable(this->loop.execute_flag)); 8193361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri move_outer_block_inside(ir, &if_execute->then_instructions); 8203361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir->insert_after(if_execute); 8213361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 8223361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 8233361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 8243361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri --this->loop.nesting_depth; 8253361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri --this->function.nesting_depth; 8263361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 8273361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 8283361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri virtual void visit(ir_loop *ir) 8293361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri { 830e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* Visit the body of the loop, with a fresh data structure in 831e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * this->loop so that the analysis we do here won't bleed into 832e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * enclosing loops. 833e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * 834e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * We assume that all code after a loop is reachable from the 835e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * loop (see comments on enum jump_strength), so the 836e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * DEAD_CODE_ELIMINATION postcondition is automatically 837e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * satisfied, as is the block.min_strength portion of the 838e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * ANALYSIS postcondition. 839e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * 840e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * The block.may_clear_execute_flag portion of the ANALYSIS 841e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * postcondition is automatically satisfied because execute 842e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * flags do not propagate outside of loops. 843e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * 844e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * The loop.may_set_return_flag portion of the ANALYSIS 845e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * postcondition is handled below. 846e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 8473361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ++this->function.nesting_depth; 8483361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri loop_record saved_loop = this->loop; 8493361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->loop = loop_record(this->function.signature, ir); 8503361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 851e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* Recursively lower nested jumps. This satisfies the 852e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * CONTAINED_JUMPS_LOWERED postcondition, except in the case of 853e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * an unconditional continue or return at the bottom of the 85403145ba655ad9173a74b853843eccaae78ff392fPaul Berry * loop, which are handled below. 855e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 8563361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri block_record body = visit_block(&ir->body_instructions); 8573361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 85803145ba655ad9173a74b853843eccaae78ff392fPaul Berry /* If the loop ends in an unconditional continue, eliminate it 85903145ba655ad9173a74b853843eccaae78ff392fPaul Berry * because it is redundant. 86003145ba655ad9173a74b853843eccaae78ff392fPaul Berry */ 86103145ba655ad9173a74b853843eccaae78ff392fPaul Berry ir_instruction *ir_last 86203145ba655ad9173a74b853843eccaae78ff392fPaul Berry = (ir_instruction *) ir->body_instructions.get_tail(); 86303145ba655ad9173a74b853843eccaae78ff392fPaul Berry if (get_jump_strength(ir_last) == strength_continue) { 86403145ba655ad9173a74b853843eccaae78ff392fPaul Berry ir_last->remove(); 86503145ba655ad9173a74b853843eccaae78ff392fPaul Berry } 86603145ba655ad9173a74b853843eccaae78ff392fPaul Berry 86703145ba655ad9173a74b853843eccaae78ff392fPaul Berry /* If the loop ends in an unconditional return, and we are 86803145ba655ad9173a74b853843eccaae78ff392fPaul Berry * lowering returns, lower it. 86903145ba655ad9173a74b853843eccaae78ff392fPaul Berry */ 87003145ba655ad9173a74b853843eccaae78ff392fPaul Berry if (this->function.lower_return) 87103145ba655ad9173a74b853843eccaae78ff392fPaul Berry lower_return_unconditionally(ir_last); 87203145ba655ad9173a74b853843eccaae78ff392fPaul Berry 8733361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(body.min_strength >= strength_break) { 874e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* FINISHME: If the min_strength of the loop body is 875e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * strength_break or strength_return, that means that it 876e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * isn't a loop at all, since control flow always leaves the 877e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * body of the loop via break or return. In principle the 878e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * loop could be eliminated in this case. This optimization 879e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * is not implemented yet. 880e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 8813361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 8823361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 8833361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(this->loop.break_flag) { 884067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry /* We only get here if we are lowering breaks */ 885067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry assert (lower_break); 886067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry 887e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* If a break flag was generated while visiting the body of 888e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * the loop, then at least one break was lowered, so we need 889e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * to generate an if statement at the end of the loop that 890e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * does a "break" if the break flag is set. The break we 891e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * generate won't violate the CONTAINED_JUMPS_LOWERED 892e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * postcondition, because should_lower_jump() always returns 893e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * false for a break that happens at the end of a loop. 894067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry * 895067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry * However, if the loop already ends in a conditional or 896067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry * unconditional break, then we need to lower that break, 897067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry * because it won't be at the end of the loop anymore. 898e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 899067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry lower_final_breaks(&ir->body_instructions); 900067c9d7bd776260298ceabda026425ed7e4eb161Paul Berry 9013361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_if* break_if = new(ir) ir_if(new(ir) ir_dereference_variable(this->loop.break_flag)); 9023361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri break_if->then_instructions.push_tail(new(ir) ir_loop_jump(ir_loop_jump::jump_break)); 9033361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir->body_instructions.push_tail(break_if); 9043361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 9053361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 906e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* If the body of the loop may set the return flag, then at 907e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * least one return was lowered to a break, so we need to ensure 908e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * that the return flag is checked after the body of the loop is 909e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * executed. 910e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 9113361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(this->loop.may_set_return_flag) { 9123361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri assert(this->function.return_flag); 913e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* Generate the if statement to check the return flag */ 9143361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_if* return_if = new(ir) ir_if(new(ir) ir_dereference_variable(this->function.return_flag)); 915e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* Note: we also need to propagate the knowledge that the 916e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * return flag may get set to the outer context. This 917e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * satisfies the loop.may_set_return_flag part of the 918e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * ANALYSIS postcondition. 919e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 920ef534f3838f23d757a40426728789183ed36c3bbFabian Bieler saved_loop.may_set_return_flag = true; 921ef534f3838f23d757a40426728789183ed36c3bbFabian Bieler if(saved_loop.loop) 922e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* If this loop is nested inside another one, then the if 923e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * statement that we generated should break out of that 924e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * loop if the return flag is set. Caller will lower that 925e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * break statement if necessary. 926e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 927ef534f3838f23d757a40426728789183ed36c3bbFabian Bieler return_if->then_instructions.push_tail(new(ir) ir_loop_jump(ir_loop_jump::jump_break)); 928ef534f3838f23d757a40426728789183ed36c3bbFabian Bieler else 929e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* Otherwise, all we need to do is ensure that the 930e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * instructions that follow are only executed if the 931e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * return flag is clear. We can do that by moving those 932e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * instructions into the else clause of the generated if 933e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * statement. 934e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 935ef534f3838f23d757a40426728789183ed36c3bbFabian Bieler move_outer_block_inside(ir, &return_if->else_instructions); 9363361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir->insert_after(return_if); 9373361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 9383361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 9393361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->loop = saved_loop; 9403361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri --this->function.nesting_depth; 9413361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 9423361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 9433361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri virtual void visit(ir_function_signature *ir) 9443361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri { 9453361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri /* these are not strictly necessary */ 9463361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri assert(!this->function.signature); 9473361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri assert(!this->loop.loop); 9483361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 949dbaa2e627effbe1361e1a69c23cf247cf86f2709Paul Berry bool lower_return; 950dbaa2e627effbe1361e1a69c23cf247cf86f2709Paul Berry if (strcmp(ir->function_name(), "main") == 0) 951dbaa2e627effbe1361e1a69c23cf247cf86f2709Paul Berry lower_return = lower_main_return; 952dbaa2e627effbe1361e1a69c23cf247cf86f2709Paul Berry else 953dbaa2e627effbe1361e1a69c23cf247cf86f2709Paul Berry lower_return = lower_sub_return; 954dbaa2e627effbe1361e1a69c23cf247cf86f2709Paul Berry 9553361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri function_record saved_function = this->function; 9563361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri loop_record saved_loop = this->loop; 957dbaa2e627effbe1361e1a69c23cf247cf86f2709Paul Berry this->function = function_record(ir, lower_return); 9583361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->loop = loop_record(ir); 9593361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 9603361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri assert(!this->loop.loop); 961e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry 962e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry /* Visit the body of the function to lower any jumps that occur 963e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * in it, except possibly an unconditional return statement at 964e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry * the end of it. 965e2c748aec5363981a05f21f26a0c4d37ccf6419dPaul Berry */ 9663361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri visit_block(&ir->body); 9673361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 968afc9a50fba39df520046019c6993d7b7559329eaPaul Berry /* If the body ended in an unconditional return of non-void, 969afc9a50fba39df520046019c6993d7b7559329eaPaul Berry * then we don't need to lower it because it's the one canonical 970afc9a50fba39df520046019c6993d7b7559329eaPaul Berry * return. 971afc9a50fba39df520046019c6993d7b7559329eaPaul Berry * 972afc9a50fba39df520046019c6993d7b7559329eaPaul Berry * If the body ended in a return of void, eliminate it because 973afc9a50fba39df520046019c6993d7b7559329eaPaul Berry * it is redundant. 974afc9a50fba39df520046019c6993d7b7559329eaPaul Berry */ 975afc9a50fba39df520046019c6993d7b7559329eaPaul Berry if (ir->return_type->is_void() && 976afc9a50fba39df520046019c6993d7b7559329eaPaul Berry get_jump_strength((ir_instruction *) ir->body.get_tail())) { 977afc9a50fba39df520046019c6993d7b7559329eaPaul Berry ir_jump *jump = (ir_jump *) ir->body.get_tail(); 978afc9a50fba39df520046019c6993d7b7559329eaPaul Berry assert (jump->ir_type == ir_type_return); 979afc9a50fba39df520046019c6993d7b7559329eaPaul Berry jump->remove(); 980afc9a50fba39df520046019c6993d7b7559329eaPaul Berry } 981afc9a50fba39df520046019c6993d7b7559329eaPaul Berry 9823361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri if(this->function.return_value) 9833361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir->body.push_tail(new(ir) ir_return(new (ir) ir_dereference_variable(this->function.return_value))); 9843361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 9853361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->loop = saved_loop; 9863361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri this->function = saved_function; 9873361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 9883361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 9893361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri virtual void visit(class ir_function * ir) 9903361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri { 9913361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri visit_block(&ir->signatures); 9923361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } 9933361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri}; 9943361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 9953361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieribool 9963361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbierido_lower_jumps(exec_list *instructions, bool pull_out_jumps, bool lower_sub_return, bool lower_main_return, bool lower_continue, bool lower_break) 9973361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri{ 9983361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri ir_lower_jumps_visitor v; 9993361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri v.pull_out_jumps = pull_out_jumps; 10003361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri v.lower_continue = lower_continue; 10013361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri v.lower_break = lower_break; 10023361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri v.lower_sub_return = lower_sub_return; 10033361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri v.lower_main_return = lower_main_return; 10043361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 10053361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri do { 10063361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri v.progress = false; 10073361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri visit_exec_list(instructions, &v); 10083361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri } while (v.progress); 10093361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri 10103361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri return v.progress; 10113361cbac2a883818efeb2b3e27405eeefce60f63Luca Barbieri} 1012