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      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 DEALINGS
     21  * IN THE SOFTWARE.
     22  *
     23  * Authors:
     24  *    Connor Abbott (cwabbott0 (at) gmail.com)
     25  *
     26  */
     27 
     28 #include "nir.h"
     29 
     30 static void
     31 add_var_use_intrinsic(nir_intrinsic_instr *instr, struct set *live,
     32                       nir_variable_mode modes)
     33 {
     34    unsigned num_vars = nir_intrinsic_infos[instr->intrinsic].num_variables;
     35 
     36    switch (instr->intrinsic) {
     37    case nir_intrinsic_copy_var:
     38       _mesa_set_add(live, instr->variables[1]->var);
     39       /* Fall through */
     40    case nir_intrinsic_store_var: {
     41       /* The first source in both copy_var and store_var is the destination.
     42        * If the variable is a local that never escapes the shader, then we
     43        * don't mark it as live for just a store.
     44        */
     45       nir_variable_mode mode = instr->variables[0]->var->data.mode;
     46       if (!(mode & (nir_var_local | nir_var_global | nir_var_shared)))
     47          _mesa_set_add(live, instr->variables[0]->var);
     48       break;
     49    }
     50 
     51    /* This pass can't be used on I/O variables after they've been lowered. */
     52    case nir_intrinsic_load_input:
     53       assert(!(modes & nir_var_shader_in));
     54       break;
     55    case nir_intrinsic_store_output:
     56       assert(!(modes & nir_var_shader_out));
     57       break;
     58 
     59    default:
     60       for (unsigned i = 0; i < num_vars; i++) {
     61          _mesa_set_add(live, instr->variables[i]->var);
     62       }
     63       break;
     64    }
     65 }
     66 
     67 static void
     68 add_var_use_call(nir_call_instr *instr, struct set *live)
     69 {
     70    if (instr->return_deref != NULL) {
     71       nir_variable *var = instr->return_deref->var;
     72       _mesa_set_add(live, var);
     73    }
     74 
     75    for (unsigned i = 0; i < instr->num_params; i++) {
     76       nir_variable *var = instr->params[i]->var;
     77       _mesa_set_add(live, var);
     78    }
     79 }
     80 
     81 static void
     82 add_var_use_tex(nir_tex_instr *instr, struct set *live)
     83 {
     84    if (instr->texture != NULL) {
     85       nir_variable *var = instr->texture->var;
     86       _mesa_set_add(live, var);
     87    }
     88 
     89    if (instr->sampler != NULL) {
     90       nir_variable *var = instr->sampler->var;
     91       _mesa_set_add(live, var);
     92    }
     93 }
     94 
     95 static void
     96 add_var_use_shader(nir_shader *shader, struct set *live, nir_variable_mode modes)
     97 {
     98    nir_foreach_function(function, shader) {
     99       if (function->impl) {
    100          nir_foreach_block(block, function->impl) {
    101             nir_foreach_instr(instr, block) {
    102                switch(instr->type) {
    103                case nir_instr_type_intrinsic:
    104                   add_var_use_intrinsic(nir_instr_as_intrinsic(instr), live,
    105                                         modes);
    106                   break;
    107 
    108                case nir_instr_type_call:
    109                   add_var_use_call(nir_instr_as_call(instr), live);
    110                   break;
    111 
    112                case nir_instr_type_tex:
    113                   add_var_use_tex(nir_instr_as_tex(instr), live);
    114                   break;
    115 
    116                default:
    117                   break;
    118                }
    119             }
    120          }
    121       }
    122    }
    123 }
    124 
    125 static void
    126 remove_dead_var_writes(nir_shader *shader, struct set *live)
    127 {
    128    nir_foreach_function(function, shader) {
    129       if (!function->impl)
    130          continue;
    131 
    132       nir_foreach_block(block, function->impl) {
    133          nir_foreach_instr_safe(instr, block) {
    134             if (instr->type != nir_instr_type_intrinsic)
    135                continue;
    136 
    137             nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
    138             if (intrin->intrinsic != nir_intrinsic_copy_var &&
    139                 intrin->intrinsic != nir_intrinsic_store_var)
    140                continue;
    141 
    142             /* Stores to dead variables need to be removed */
    143             if (intrin->variables[0]->var->data.mode == 0)
    144                nir_instr_remove(instr);
    145          }
    146       }
    147    }
    148 }
    149 
    150 static bool
    151 remove_dead_vars(struct exec_list *var_list, struct set *live)
    152 {
    153    bool progress = false;
    154 
    155    foreach_list_typed_safe(nir_variable, var, node, var_list) {
    156       struct set_entry *entry = _mesa_set_search(live, var);
    157       if (entry == NULL) {
    158          /* Mark this variable as used by setting the mode to 0 */
    159          var->data.mode = 0;
    160          exec_node_remove(&var->node);
    161          progress = true;
    162       }
    163    }
    164 
    165    return progress;
    166 }
    167 
    168 bool
    169 nir_remove_dead_variables(nir_shader *shader, nir_variable_mode modes)
    170 {
    171    bool progress = false;
    172    struct set *live =
    173       _mesa_set_create(NULL, _mesa_hash_pointer, _mesa_key_pointer_equal);
    174 
    175    add_var_use_shader(shader, live, modes);
    176 
    177    if (modes & nir_var_uniform)
    178       progress = remove_dead_vars(&shader->uniforms, live) || progress;
    179 
    180    if (modes & nir_var_shader_in)
    181       progress = remove_dead_vars(&shader->inputs, live) || progress;
    182 
    183    if (modes & nir_var_shader_out)
    184       progress = remove_dead_vars(&shader->outputs, live) || progress;
    185 
    186    if (modes & nir_var_global)
    187       progress = remove_dead_vars(&shader->globals, live) || progress;
    188 
    189    if (modes & nir_var_system_value)
    190       progress = remove_dead_vars(&shader->system_values, live) || progress;
    191 
    192    if (modes & nir_var_shared)
    193       progress = remove_dead_vars(&shader->shared, live) || progress;
    194 
    195    if (modes & nir_var_local) {
    196       nir_foreach_function(function, shader) {
    197          if (function->impl) {
    198             if (remove_dead_vars(&function->impl->locals, live))
    199                progress = true;
    200          }
    201       }
    202    }
    203 
    204    if (progress) {
    205       remove_dead_var_writes(shader, live);
    206 
    207       nir_foreach_function(function, shader) {
    208          if (function->impl) {
    209             nir_metadata_preserve(function->impl, nir_metadata_block_index |
    210                                                   nir_metadata_dominance);
    211          }
    212       }
    213    }
    214 
    215    _mesa_set_destroy(live, NULL);
    216    return progress;
    217 }
    218