src/glsl/lower_vec_index_to_swizzle.cpp

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