src/compiler/nir/nir_linking_helpers.c

   1 /*
   2  * Copyright © 2015 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
  24 #include "nir.h"
  25 #include "util/set.h"
  26 #include "util/hash_table.h"
  27
  28 /* This file contains various little helpers for doing simple linking in
  29  * NIR.  Eventually, we'll probably want a full-blown varying packing
  30  * implementation in here.  Right now, it just deletes unused things.
  31  */
  32
  33 /**
  34  * Returns the bits in the inputs_read, outputs_written, or
  35  * system_values_read bitfield corresponding to this variable.
  36  */
  37 static uint64_t
  38 get_variable_io_mask(nir_variable *var, gl_shader_stage stage)
  39 {
  40    /* TODO: add support for tess patches */
  41    if (var->data.patch || var->data.location < 0)
  42       return 0;
  43
  44    assert(var->data.mode == nir_var_shader_in ||
  45           var->data.mode == nir_var_shader_out ||
  46           var->data.mode == nir_var_system_value);
  47    assert(var->data.location >= 0);
  48
  49    const struct glsl_type *type = var->type;
  50    if (nir_is_per_vertex_io(var, stage)) {
  51       assert(glsl_type_is_array(type));
  52       type = glsl_get_array_element(type);
  53    }
  54
  55    unsigned slots = glsl_count_attribute_slots(type, false);
  56    return ((1ull << slots) - 1) << var->data.location;
  57 }
  58
  59 static void
  60 tcs_add_output_reads(nir_shader *shader, uint64_t *read)
  61 {
  62    nir_foreach_function(function, shader) {
  63       if (function->impl) {
  64          nir_foreach_block(block, function->impl) {
  65             nir_foreach_instr(instr, block) {
  66                if (instr->type != nir_instr_type_intrinsic)
  67                   continue;
  68
  69                nir_intrinsic_instr *intrin_instr =
  70                   nir_instr_as_intrinsic(instr);
  71                if (intrin_instr->intrinsic == nir_intrinsic_load_var &&
  72                    intrin_instr->variables[0]->var->data.mode ==
  73                    nir_var_shader_out) {
  74
  75                   nir_variable *var = intrin_instr->variables[0]->var;
  76                   read[var->data.location_frac] |=
  77                      get_variable_io_mask(intrin_instr->variables[0]->var,
  78                                           shader->stage);
  79                }
  80             }
  81          }
  82       }
  83    }
  84 }
  85
  86 static bool
  87 remove_unused_io_vars(nir_shader *shader, struct exec_list *var_list,
  88                       uint64_t *used_by_other_stage)
  89 {
  90    bool progress = false;
  91
  92    nir_foreach_variable_safe(var, var_list) {
  93       /* TODO: add patch support */
  94       if (var->data.patch)
  95          continue;
  96
  97       if (var->data.location < VARYING_SLOT_VAR0 && var->data.location >= 0)
  98          continue;
  99
 100       if (var->data.always_active_io)
 101          continue;
 102
 103       uint64_t other_stage = used_by_other_stage[var->data.location_frac];
 104
 105       if (!(other_stage & get_variable_io_mask(var, shader->stage))) {
 106          /* This one is invalid, make it a global variable instead */
 107          var->data.location = 0;
 108          var->data.mode = nir_var_global;
 109
 110          exec_node_remove(&var->node);
 111          exec_list_push_tail(&shader->globals, &var->node);
 112
 113          progress = true;
 114       }
 115    }
 116
 117    return progress;
 118 }
 119
 120 bool
 121 nir_remove_unused_varyings(nir_shader *producer, nir_shader *consumer)
 122 {
 123    assert(producer->stage != MESA_SHADER_FRAGMENT);
 124    assert(consumer->stage != MESA_SHADER_VERTEX);
 125
 126    uint64_t read[4] = { 0 }, written[4] = { 0 };
 127
 128    nir_foreach_variable(var, &producer->outputs) {
 129       written[var->data.location_frac] |=
 130          get_variable_io_mask(var, producer->stage);
 131    }
 132
 133    nir_foreach_variable(var, &consumer->inputs) {
 134       read[var->data.location_frac] |=
 135          get_variable_io_mask(var, consumer->stage);
 136    }
 137
 138    /* Each TCS invocation can read data written by other TCS invocations,
 139     * so even if the outputs are not used by the TES we must also make
 140     * sure they are not read by the TCS before demoting them to globals.
 141     */
 142    if (producer->stage == MESA_SHADER_TESS_CTRL)
 143       tcs_add_output_reads(producer, read);
 144
 145    bool progress = false;
 146    progress = remove_unused_io_vars(producer, &producer->outputs, read);
 147
 148    progress =
 149       remove_unused_io_vars(consumer, &consumer->inputs, written) || progress;
 150
 151    return progress;
 152 }