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_rvalue_visitor.h"
34 #include "ir_optimization.h"
35 #include "compiler/glsl_types.h"
36 #include "main/macros.h"
37
38 namespace {
39
40 class ir_vec_index_to_swizzle_visitor : public ir_rvalue_visitor {
41 public:
ir_vec_index_to_swizzle_visitor()42 ir_vec_index_to_swizzle_visitor()
43 {
44 progress = false;
45 }
46
47 ir_rvalue *convert_vector_extract_to_swizzle(ir_rvalue *val);
48
49 virtual void handle_rvalue(ir_rvalue **);
50
51 bool progress;
52 };
53
54 } /* anonymous namespace */
55
56 void
handle_rvalue(ir_rvalue ** rv)57 ir_vec_index_to_swizzle_visitor::handle_rvalue(ir_rvalue **rv)
58 {
59 if (*rv == NULL)
60 return;
61
62 ir_expression *const expr = (*rv)->as_expression();
63 if (expr == NULL || expr->operation != ir_binop_vector_extract)
64 return;
65
66 ir_constant *const idx = expr->operands[1]->constant_expression_value();
67 if (idx == NULL)
68 return;
69
70 void *ctx = ralloc_parent(expr);
71 this->progress = true;
72
73 /* Page 40 of the GLSL 1.20 spec says:
74 *
75 * "When indexing with non-constant expressions, behavior is undefined
76 * if the index is negative, or greater than or equal to the size of
77 * the vector."
78 *
79 * The quoted spec text mentions non-constant expressions, but this code
80 * operates on constants. These constants are the result of non-constant
81 * expressions that have been optimized to constants. The common case here
82 * is a loop counter from an unrolled loop that is used to index a vector.
83 *
84 * The ir_swizzle constructor gets angry if the index is negative or too
85 * large. For simplicity sake, just clamp the index to [0, size-1].
86 */
87 const int i = CLAMP(idx->value.i[0], 0,
88 (int) expr->operands[0]->type->vector_elements - 1);
89
90 *rv = new(ctx) ir_swizzle(expr->operands[0], i, 0, 0, 0, 1);
91 }
92
93 bool
do_vec_index_to_swizzle(exec_list * instructions)94 do_vec_index_to_swizzle(exec_list *instructions)
95 {
96 ir_vec_index_to_swizzle_visitor v;
97
98 v.run(instructions);
99
100 return v.progress;
101 }
102