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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 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 
42 class ir_vec_index_to_swizzle_visitor : public ir_hierarchical_visitor {
43 public:
ir_vec_index_to_swizzle_visitor()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 
61 ir_rvalue *
convert_vec_index_to_swizzle(ir_rvalue * ir)62 ir_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 
101 ir_visitor_status
visit_enter(ir_expression * ir)102 ir_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 
113 ir_visitor_status
visit_enter(ir_swizzle * ir)114 ir_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 
125 ir_visitor_status
visit_enter(ir_assignment * ir)126 ir_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 
134 ir_visitor_status
visit_enter(ir_call * ir)135 ir_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 
149 ir_visitor_status
visit_enter(ir_return * ir)150 ir_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 
159 ir_visitor_status
visit_enter(ir_if * ir)160 ir_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 
167 bool
do_vec_index_to_swizzle(exec_list * instructions)168 do_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