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  1. /*
  2.  * Copyright © 2010 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
  21.  * DEALINGS IN THE SOFTWARE.
  22.  */
  23.  
  24. /**
  25.  * \file ir_basic_block.cpp
  26.  *
  27.  * Basic block analysis of instruction streams.
  28.  */
  29.  
  30. #include "ir.h"
  31. #include "ir_visitor.h"
  32. #include "ir_basic_block.h"
  33. #include "glsl_types.h"
  34.  
  35. class ir_has_call_visitor : public ir_hierarchical_visitor {
  36. public:
  37.    ir_has_call_visitor()
  38.    {
  39.       has_call = false;
  40.    }
  41.  
  42.    virtual ir_visitor_status visit_enter(ir_call *ir)
  43.    {
  44.       (void) ir;
  45.       has_call = true;
  46.       return visit_stop;
  47.    }
  48.  
  49.    bool has_call;
  50. };
  51.  
  52. bool
  53. ir_has_call(ir_instruction *ir)
  54. {
  55.    ir_has_call_visitor v;
  56.    ir->accept(&v);
  57.    return v.has_call;
  58. }
  59.  
  60. /**
  61.  * Calls a user function for every basic block in the instruction stream.
  62.  *
  63.  * Basic block analysis is pretty easy in our IR thanks to the lack of
  64.  * unstructured control flow.  We've got:
  65.  *
  66.  * ir_loop (for () {}, while () {}, do {} while ())
  67.  * ir_loop_jump (
  68.  * ir_if () {}
  69.  * ir_return
  70.  * ir_call()
  71.  *
  72.  * Note that the basic blocks returned by this don't encompass all
  73.  * operations performed by the program -- for example, if conditions
  74.  * don't get returned, nor do the assignments that will be generated
  75.  * for ir_call parameters.
  76.  */
  77. void call_for_basic_blocks(exec_list *instructions,
  78.                            void (*callback)(ir_instruction *first,
  79.                                             ir_instruction *last,
  80.                                             void *data),
  81.                            void *data)
  82. {
  83.    ir_instruction *leader = NULL;
  84.    ir_instruction *last = NULL;
  85.  
  86.    foreach_iter(exec_list_iterator, iter, *instructions) {
  87.       ir_instruction *ir = (ir_instruction *)iter.get();
  88.       ir_if *ir_if;
  89.       ir_loop *ir_loop;
  90.       ir_function *ir_function;
  91.  
  92.       if (!leader)
  93.          leader = ir;
  94.  
  95.       if ((ir_if = ir->as_if())) {
  96.          callback(leader, ir, data);
  97.          leader = NULL;
  98.  
  99.          call_for_basic_blocks(&ir_if->then_instructions, callback, data);
  100.          call_for_basic_blocks(&ir_if->else_instructions, callback, data);
  101.       } else if ((ir_loop = ir->as_loop())) {
  102.          callback(leader, ir, data);
  103.          leader = NULL;
  104.          call_for_basic_blocks(&ir_loop->body_instructions, callback, data);
  105.       } else if (ir->as_return() || ir->as_call()) {
  106.          callback(leader, ir, data);
  107.          leader = NULL;
  108.       } else if ((ir_function = ir->as_function())) {
  109.          /* A function definition doesn't interrupt our basic block
  110.           * since execution doesn't go into it.  We should process the
  111.           * bodies of its signatures for BBs, though.
  112.           *
  113.           * Note that we miss an opportunity for producing more
  114.           * maximal BBs between the instructions that precede main()
  115.           * and the body of main().  Perhaps those instructions ought
  116.           * to live inside of main().
  117.           */
  118.          foreach_iter(exec_list_iterator, fun_iter, *ir_function) {
  119.             ir_function_signature *ir_sig;
  120.  
  121.             ir_sig = (ir_function_signature *)fun_iter.get();
  122.  
  123.             call_for_basic_blocks(&ir_sig->body, callback, data);
  124.          }
  125.       } else if (ir->as_assignment()) {
  126.          /* If there's a call in the expression tree being assigned,
  127.           * then that ends the BB too.
  128.           *
  129.           * The assumption is that any consumer of the basic block
  130.           * walker is fine with the fact that the call is somewhere in
  131.           * the tree even if portions of the tree may be evaluated
  132.           * after the call.
  133.           *
  134.           * A consumer that has an issue with this could not process
  135.           * the last instruction of the basic block.  If doing so,
  136.           * expression flattener may be useful before using the basic
  137.           * block finder to get more maximal basic blocks out.
  138.           */
  139.          if (ir_has_call(ir)) {
  140.             callback(leader, ir, data);
  141.             leader = NULL;
  142.          }
  143.       }
  144.       last = ir;
  145.    }
  146.    if (leader) {
  147.       callback(leader, last, data);
  148.    }
  149. }
  150.