src/compiler/nir/nir_loop_analyze.h

   1 /*
   2  * Copyright © 2016 Intel Corporation
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  21  * IN THE SOFTWARE.
  22  */
  23
  24 #pragma once
  25
  26 #include "nir.h"
  27
  28 /* Returns true if nir_cf_node contains a jump other than the expected_jump
  29  * parameter.
  30  */
  31 static inline bool
  32 contains_other_jump(nir_cf_node *node, nir_instr *expected_jump)
  33 {
  34    switch (node->type) {
  35    case nir_cf_node_block: {
  36       nir_instr *lst_instr = nir_block_last_instr(nir_cf_node_as_block(node));
  37
  38       /* dead_cf should have eliminated any instruction after the first break
  39        */
  40       nir_foreach_instr(instr, nir_cf_node_as_block(node))
  41          assert(instr->type != nir_instr_type_jump || instr == lst_instr);
  42
  43       if (lst_instr && lst_instr->type == nir_instr_type_jump &&
  44           lst_instr != expected_jump)
  45          return true;
  46       else
  47          return false;
  48    }
  49    case nir_cf_node_if: {
  50       nir_if *if_stmt = nir_cf_node_as_if(node);
  51
  52       foreach_list_typed_safe(nir_cf_node, node, node, &if_stmt->then_list) {
  53          if (contains_other_jump(node, expected_jump))
  54             return true;
  55       }
  56
  57       foreach_list_typed_safe(nir_cf_node, node, node, &if_stmt->else_list) {
  58          if (contains_other_jump(node, expected_jump))
  59             return true;
  60       }
  61
  62       return false;
  63    }
  64    case nir_cf_node_loop:
  65       return true;
  66
  67    default:
  68       unreachable("Unhandled cf node type");
  69    }
  70 }
  71
  72 /* Here we define a trivial if as containing only a single break that must be
  73  * located at the end of either the then or else branch of the top level if,
  74  * there must be no other breaks or any other type of jump.  Or we pass NULL
  75  * to break_block the if must contains no jumps at all.
  76  */
  77 static inline bool
  78 nir_is_trivial_loop_if(nir_if *nif, nir_block *break_block)
  79 {
  80    nir_instr *last_instr = NULL;
  81
  82    if (break_block) {
  83       last_instr = nir_block_last_instr(break_block);
  84       assert(last_instr && last_instr->type == nir_instr_type_jump &&
  85              nir_instr_as_jump(last_instr)->type == nir_jump_break);
  86    }
  87
  88    if (contains_other_jump(&nif->cf_node, last_instr))
  89       return false;
  90
  91    return true;
  92 }