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
35class ir_has_call_visitor : public ir_hierarchical_visitor {
36public:
37   ir_has_call_visitor()
38   {
39      has_call = false;
40   }
41
42   using ir_hierarchical_visitor::visit_enter;
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
53bool
54ir_has_call(ir_instruction *ir)
55{
56   ir_has_call_visitor v;
57   ir->accept(&v);
58   return v.has_call;
59}
60
61/**
62 * Calls a user function for every basic block in the instruction stream.
63 *
64 * Basic block analysis is pretty easy in our IR thanks to the lack of
65 * unstructured control flow.  We've got:
66 *
67 * ir_loop (for () {}, while () {}, do {} while ())
68 * ir_loop_jump (
69 * ir_if () {}
70 * ir_return
71 * ir_call()
72 *
73 * Note that the basic blocks returned by this don't encompass all
74 * operations performed by the program -- for example, if conditions
75 * don't get returned, nor do the assignments that will be generated
76 * for ir_call parameters.
77 */
78void call_for_basic_blocks(exec_list *instructions,
79			   void (*callback)(ir_instruction *first,
80					    ir_instruction *last,
81					    void *data),
82			   void *data)
83{
84   ir_instruction *leader = NULL;
85   ir_instruction *last = NULL;
86
87   foreach_iter(exec_list_iterator, iter, *instructions) {
88      ir_instruction *ir = (ir_instruction *)iter.get();
89      ir_if *ir_if;
90      ir_loop *ir_loop;
91      ir_function *ir_function;
92
93      if (!leader)
94	 leader = ir;
95
96      if ((ir_if = ir->as_if())) {
97	 callback(leader, ir, data);
98	 leader = NULL;
99
100	 call_for_basic_blocks(&ir_if->then_instructions, callback, data);
101	 call_for_basic_blocks(&ir_if->else_instructions, callback, data);
102      } else if ((ir_loop = ir->as_loop())) {
103	 callback(leader, ir, data);
104	 leader = NULL;
105	 call_for_basic_blocks(&ir_loop->body_instructions, callback, data);
106      } else if (ir->as_return() || ir->as_call()) {
107	 callback(leader, ir, data);
108	 leader = NULL;
109      } else if ((ir_function = ir->as_function())) {
110	 /* A function definition doesn't interrupt our basic block
111	  * since execution doesn't go into it.  We should process the
112	  * bodies of its signatures for BBs, though.
113	  *
114	  * Note that we miss an opportunity for producing more
115	  * maximal BBs between the instructions that precede main()
116	  * and the body of main().  Perhaps those instructions ought
117	  * to live inside of main().
118	  */
119	 foreach_iter(exec_list_iterator, fun_iter, *ir_function) {
120	    ir_function_signature *ir_sig;
121
122	    ir_sig = (ir_function_signature *)fun_iter.get();
123
124	    call_for_basic_blocks(&ir_sig->body, callback, data);
125	 }
126      } else if (ir->as_assignment()) {
127	 /* If there's a call in the expression tree being assigned,
128	  * then that ends the BB too.
129	  *
130	  * The assumption is that any consumer of the basic block
131	  * walker is fine with the fact that the call is somewhere in
132	  * the tree even if portions of the tree may be evaluated
133	  * after the call.
134	  *
135	  * A consumer that has an issue with this could not process
136	  * the last instruction of the basic block.  If doing so,
137	  * expression flattener may be useful before using the basic
138	  * block finder to get more maximal basic blocks out.
139	  */
140	 if (ir_has_call(ir)) {
141	    callback(leader, ir, data);
142	    leader = NULL;
143	 }
144      }
145      last = ir;
146   }
147   if (leader) {
148      callback(leader, last, data);
149   }
150}
151