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 uint64_t
  60 tcs_output_read_bitmask(nir_shader *shader)
  61 {
  62    uint64_t read = 0;
  63
  64    nir_foreach_function(function, shader) {
  65       if (function->impl) {
  66          nir_foreach_block(block, function->impl) {
  67             nir_foreach_instr(instr, block) {
  68                if (instr->type != nir_instr_type_intrinsic)
  69                   continue;
  70
  71                nir_intrinsic_instr *intrin_instr =
  72                   nir_instr_as_intrinsic(instr);
  73                if (intrin_instr->intrinsic == nir_intrinsic_load_var &&
  74                    intrin_instr->variables[0]->var->data.mode ==
  75                    nir_var_shader_out) {
  76                   read |= get_variable_io_mask(intrin_instr->variables[0]->var,
  77                                                shader->stage);
  78                }
  79             }
  80          }
  81       }
  82    }
  83
  84    return read;
  85 }
  86
  87 static bool
  88 remove_unused_io_vars(nir_shader *shader, struct exec_list *var_list,
  89                       uint64_t used_by_other_stage)
  90 {
  91    bool progress = false;
  92
  93    nir_foreach_variable_safe(var, var_list) {
  94       /* TODO: add patch support */
  95       if (var->data.patch)
  96          continue;
  97
  98       if (var->data.location < VARYING_SLOT_VAR0 && var->data.location >= 0)
  99          continue;
 100
 101       if (var->data.always_active_io)
 102          continue;
 103
 104       if (!(used_by_other_stage & get_variable_io_mask(var, shader->stage))) {
 105          /* This one is invalid, make it a global variable instead */
 106          var->data.location = 0;
 107          var->data.mode = nir_var_global;
 108
 109          exec_node_remove(&var->node);
 110          exec_list_push_tail(&shader->globals, &var->node);
 111
 112          progress = true;
 113       }
 114    }
 115
 116    return progress;
 117 }
 118
 119 bool
 120 nir_remove_unused_varyings(nir_shader *producer, nir_shader *consumer)
 121 {
 122    assert(producer->stage != MESA_SHADER_FRAGMENT);
 123    assert(consumer->stage != MESA_SHADER_VERTEX);
 124
 125    uint64_t read = 0, written = 0;
 126
 127    nir_foreach_variable(var, &producer->outputs)
 128       written |= get_variable_io_mask(var, producer->stage);
 129
 130    nir_foreach_variable(var, &consumer->inputs)
 131       read |= get_variable_io_mask(var, consumer->stage);
 132
 133    /* Each TCS invocation can read data written by other TCS invocations,
 134     * so even if the outputs are not used by the TES we must also make
 135     * sure they are not read by the TCS before demoting them to globals.
 136     */
 137    if (producer->stage == MESA_SHADER_TESS_CTRL)
 138       read |= tcs_output_read_bitmask(producer);
 139
 140    bool progress = false;
 141    progress = remove_unused_io_vars(producer, &producer->outputs, read);
 142
 143    progress =
 144       remove_unused_io_vars(consumer, &consumer->inputs, written) || progress;
 145
 146    return progress;
 147 }