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    {
  50       instructions = insts;
  51       stage = s;
  52       const_count = 0;
  53       progress = false;
  54    }
  55
  56    bool run()
  57    {
  58       visit_list_elements(this, instructions);
  59       return progress;
  60    }
  61
  62    ir_visitor_status visit_enter(ir_texture *);
  63    void handle_rvalue(ir_rvalue **rvalue);
  64
  65 private:
  66    exec_list *instructions;
  67    unsigned stage;
  68    unsigned const_count;
  69    bool progress;
  70 };
  71
  72 ir_visitor_status
  73 lower_const_array_visitor::visit_enter(ir_texture *)
  74 {
  75    return visit_continue_with_parent;
  76 }
  77
  78 void
  79 lower_const_array_visitor::handle_rvalue(ir_rvalue **rvalue)
  80 {
  81    if (!*rvalue)
  82       return;
  83
  84    ir_constant *con = (*rvalue)->as_constant();
  85    if (!con || !con->type->is_array())
  86       return;
  87
  88    void *mem_ctx = ralloc_parent(con);
  89
  90    /* In the very unlikely event of 4294967295 constant arrays in a single
  91     * shader, don't promote this to a uniform.
  92     */
  93    unsigned limit = ~0;
  94    if (const_count == limit)
  95       return;
  96
  97    char *uniform_name = ralloc_asprintf(mem_ctx, "constarray_%x_%u",
  98                                         const_count, stage);
  99    const_count++;
 100
 101    ir_variable *uni =
 102       new(mem_ctx) ir_variable(con->type, uniform_name, ir_var_uniform);
 103    uni->constant_initializer = con;
 104    uni->constant_value = con;
 105    uni->data.has_initializer = true;
 106    uni->data.how_declared = ir_var_hidden;
 107    uni->data.read_only = true;
 108    /* Assume the whole thing is accessed. */
 109    uni->data.max_array_access = uni->type->length - 1;
 110    instructions->push_head(uni);
 111
 112    *rvalue = new(mem_ctx) ir_dereference_variable(uni);
 113
 114    progress = true;
 115 }
 116
 117 } /* anonymous namespace */
 118
 119 bool
 120 lower_const_arrays_to_uniforms(exec_list *instructions, unsigned stage)
 121 {
 122    lower_const_array_visitor v(instructions, stage);
 123    return v.run();
 124 }