ir_basic_block.cpp

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