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 lower_vec_index_to_swizzle.cpp
26 *
27 * Turns constant indexing into vector types to swizzles.  This will
28 * let other swizzle-aware optimization passes catch these constructs,
29 * and codegen backends not have to worry about this case.
30 */
31
32#include "ir.h"
33#include "ir_visitor.h"
34#include "ir_optimization.h"
35#include "glsl_types.h"
36#include "main/macros.h"
37
38/**
39 * Visitor class for replacing expressions with ir_constant values.
40 */
41
42class ir_vec_index_to_swizzle_visitor : public ir_hierarchical_visitor {
43public:
44   ir_vec_index_to_swizzle_visitor()
45   {
46      progress = false;
47   }
48
49   ir_rvalue *convert_vec_index_to_swizzle(ir_rvalue *val);
50
51   virtual ir_visitor_status visit_enter(ir_expression *);
52   virtual ir_visitor_status visit_enter(ir_swizzle *);
53   virtual ir_visitor_status visit_enter(ir_assignment *);
54   virtual ir_visitor_status visit_enter(ir_return *);
55   virtual ir_visitor_status visit_enter(ir_call *);
56   virtual ir_visitor_status visit_enter(ir_if *);
57
58   bool progress;
59};
60
61ir_rvalue *
62ir_vec_index_to_swizzle_visitor::convert_vec_index_to_swizzle(ir_rvalue *ir)
63{
64   ir_dereference_array *deref = ir->as_dereference_array();
65   ir_constant *ir_constant;
66
67   if (!deref)
68      return ir;
69
70   if (deref->array->type->is_matrix() || deref->array->type->is_array())
71      return ir;
72
73   assert(deref->array_index->type->base_type == GLSL_TYPE_INT);
74   ir_constant = deref->array_index->constant_expression_value();
75   if (!ir_constant)
76      return ir;
77
78   void *ctx = ralloc_parent(ir);
79   this->progress = true;
80
81   /* Page 40 of the GLSL 1.20 spec says:
82    *
83    *     "When indexing with non-constant expressions, behavior is undefined
84    *     if the index is negative, or greater than or equal to the size of
85    *     the vector."
86    *
87    * The quoted spec text mentions non-constant expressions, but this code
88    * operates on constants.  These constants are the result of non-constant
89    * expressions that have been optimized to constants.  The common case here
90    * is a loop counter from an unrolled loop that is used to index a vector.
91    *
92    * The ir_swizzle constructor gets angry if the index is negative or too
93    * large.  For simplicity sake, just clamp the index to [0, size-1].
94    */
95   const int i = MIN2(MAX2(ir_constant->value.i[0], 0),
96		      (deref->array->type->vector_elements - 1));
97
98   return new(ctx) ir_swizzle(deref->array, i, 0, 0, 0, 1);
99}
100
101ir_visitor_status
102ir_vec_index_to_swizzle_visitor::visit_enter(ir_expression *ir)
103{
104   unsigned int i;
105
106   for (i = 0; i < ir->get_num_operands(); i++) {
107      ir->operands[i] = convert_vec_index_to_swizzle(ir->operands[i]);
108   }
109
110   return visit_continue;
111}
112
113ir_visitor_status
114ir_vec_index_to_swizzle_visitor::visit_enter(ir_swizzle *ir)
115{
116   /* Can't be hit from normal GLSL, since you can't swizzle a scalar (which
117    * the result of indexing a vector is.  But maybe at some point we'll end up
118    * using swizzling of scalars for vector construction.
119    */
120   ir->val = convert_vec_index_to_swizzle(ir->val);
121
122   return visit_continue;
123}
124
125ir_visitor_status
126ir_vec_index_to_swizzle_visitor::visit_enter(ir_assignment *ir)
127{
128   ir->set_lhs(convert_vec_index_to_swizzle(ir->lhs));
129   ir->rhs = convert_vec_index_to_swizzle(ir->rhs);
130
131   return visit_continue;
132}
133
134ir_visitor_status
135ir_vec_index_to_swizzle_visitor::visit_enter(ir_call *ir)
136{
137   foreach_iter(exec_list_iterator, iter, *ir) {
138      ir_rvalue *param = (ir_rvalue *)iter.get();
139      ir_rvalue *new_param = convert_vec_index_to_swizzle(param);
140
141      if (new_param != param) {
142	 param->replace_with(new_param);
143      }
144   }
145
146   return visit_continue;
147}
148
149ir_visitor_status
150ir_vec_index_to_swizzle_visitor::visit_enter(ir_return *ir)
151{
152   if (ir->value) {
153      ir->value = convert_vec_index_to_swizzle(ir->value);
154   }
155
156   return visit_continue;
157}
158
159ir_visitor_status
160ir_vec_index_to_swizzle_visitor::visit_enter(ir_if *ir)
161{
162   ir->condition = convert_vec_index_to_swizzle(ir->condition);
163
164   return visit_continue;
165}
166
167bool
168do_vec_index_to_swizzle(exec_list *instructions)
169{
170   ir_vec_index_to_swizzle_visitor v;
171
172   v.run(instructions);
173
174   return v.progress;
175}
176