src/compiler/glsl/lower_const_arrays_to_uniforms.cpp

   1 /*
   2  * Copyright © 2014 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_const_arrays_to_uniforms.cpp
  26  *
  27  * Lower constant arrays to uniform arrays.
  28  *
  29  * Some driver backends (such as i965 and nouveau) don't handle constant arrays
  30  * gracefully, instead treating them as ordinary writable temporary arrays.
  31  * Since arrays can be large, this often means spilling them to scratch memory,
  32  * which usually involves a large number of instructions.
  33  *
  34  * This must be called prior to link_set_uniform_initializers(); we need the
  35  * linker to process our new uniform's constant initializer.
  36  *
  37  * This should be called after optimizations, since those can result in
  38  * splitting and removing arrays that are indexed by constant expressions.
  39  */
  40 #include "ir.h"
  41 #include "ir_visitor.h"
  42 #include "ir_rvalue_visitor.h"
  43 #include "compiler/glsl_types.h"
  44
  45 namespace {
  46 class lower_const_array_visitor : public ir_rvalue_visitor {
  47 public:
  48    lower_const_array_visitor(exec_list *insts, unsigned s,
  49                              unsigned available_uni_components)
  50    {
  51       instructions = insts;
  52       stage = s;
  53       const_count = 0;
  54       free_uni_components = available_uni_components;
  55       progress = false;
  56    }
  57
  58    bool run()
  59    {
  60       visit_list_elements(this, instructions);
  61       return progress;
  62    }
  63
  64    ir_visitor_status visit_enter(ir_texture *);
  65    void handle_rvalue(ir_rvalue **rvalue);
  66
  67 private:
  68    exec_list *instructions;
  69    unsigned stage;
  70    unsigned const_count;
  71    unsigned free_uni_components;
  72    bool progress;
  73 };
  74
  75 ir_visitor_status
  76 lower_const_array_visitor::visit_enter(ir_texture *)
  77 {
  78    return visit_continue_with_parent;
  79 }
  80
  81 void
  82 lower_const_array_visitor::handle_rvalue(ir_rvalue **rvalue)
  83 {
  84    if (!*rvalue)
  85       return;
  86
  87    ir_constant *con = (*rvalue)->as_constant();
  88    if (!con || !con->type->is_array())
  89       return;
  90
  91    /* How many uniform component slots are required? */
  92    unsigned component_slots = con->type->component_slots();
  93
  94    /* We would utilize more than is available, bail out. */
  95    if (component_slots > free_uni_components)
  96       return;
  97
  98    free_uni_components -= component_slots;
  99
 100    void *mem_ctx = ralloc_parent(con);
 101
 102    /* In the very unlikely event of 4294967295 constant arrays in a single
 103     * shader, don't promote this to a uniform.
 104     */
 105    unsigned limit = ~0;
 106    if (const_count == limit)
 107       return;
 108
 109    char *uniform_name = ralloc_asprintf(mem_ctx, "constarray_%x_%u",
 110                                         const_count, stage);
 111    const_count++;
 112
 113    ir_variable *uni =
 114       new(mem_ctx) ir_variable(con->type, uniform_name, ir_var_uniform);
 115    uni->constant_initializer = con;
 116    uni->constant_value = con;
 117    uni->data.has_initializer = true;
 118    uni->data.how_declared = ir_var_hidden;
 119    uni->data.read_only = true;
 120    /* Assume the whole thing is accessed. */
 121    uni->data.max_array_access = uni->type->length - 1;
 122    instructions->push_head(uni);
 123
 124    *rvalue = new(mem_ctx) ir_dereference_variable(uni);
 125
 126    progress = true;
 127 }
 128
 129 } /* anonymous namespace */
 130
 131
 132 static unsigned
 133 count_uniforms(exec_list *instructions)
 134 {
 135    unsigned total = 0;
 136
 137    foreach_in_list(ir_instruction, node, instructions) {
 138       ir_variable *const var = node->as_variable();
 139
 140       if (!var || var->data.mode != ir_var_uniform)
 141          continue;
 142
 143       total += var->type->component_slots();
 144    }
 145    return total;
 146 }
 147
 148 bool
 149 lower_const_arrays_to_uniforms(exec_list *instructions, unsigned stage,
 150                                unsigned max_uniform_components)
 151 {
 152    unsigned uniform_components = count_uniforms(instructions);
 153    unsigned free_uniform_slots = max_uniform_components - uniform_components;
 154
 155    lower_const_array_visitor v(instructions, stage, free_uniform_slots);
 156    return v.run();
 157 }