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
38namespace {
39
40class ir_vec_index_to_swizzle_visitor : public ir_rvalue_visitor {
41public:
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
56void
57ir_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   void *mem_ctx = ralloc_parent(expr);
67   ir_constant *const idx =
68      expr->operands[1]->constant_expression_value(mem_ctx);
69   if (idx == NULL)
70      return;
71
72   this->progress = true;
73
74   /* Page 40 of the GLSL 1.20 spec says:
75    *
76    *     "When indexing with non-constant expressions, behavior is undefined
77    *     if the index is negative, or greater than or equal to the size of
78    *     the vector."
79    *
80    * The quoted spec text mentions non-constant expressions, but this code
81    * operates on constants.  These constants are the result of non-constant
82    * expressions that have been optimized to constants.  The common case here
83    * is a loop counter from an unrolled loop that is used to index a vector.
84    *
85    * The ir_swizzle constructor gets angry if the index is negative or too
86    * large.  For simplicity sake, just clamp the index to [0, size-1].
87    */
88   const int i = CLAMP(idx->value.i[0], 0,
89                       (int) expr->operands[0]->type->vector_elements - 1);
90
91   *rv = new(mem_ctx) ir_swizzle(expr->operands[0], i, 0, 0, 0, 1);
92}
93
94bool
95do_vec_index_to_swizzle(exec_list *instructions)
96{
97   ir_vec_index_to_swizzle_visitor v;
98
99   v.run(instructions);
100
101   return v.progress;
102}
103