src/mesa/state_tracker/st_nir_lower_builtin.c

   1 /*
   2  * Copyright © 2016 Red Hat
   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 FROM,
  20  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  21  * SOFTWARE.
  22  */
  23
  24 /* Lowering pass that lowers accesses to built-in uniform variables.
  25  * Built-in uniforms are not necessarily packed the same way that
  26  * normal uniform structs are, for example:
  27  *
  28  *    struct gl_FogParameters {
  29  *       vec4 color;
  30  *       float density;
  31  *       float start;
  32  *       float end;
  33  *       float scale;
  34  *    };
  35  *
  36  * is packed into vec4[2], whereas the same struct would be packed
  37  * (by gallium), as vec4[5] if it where not built-in.  Because of
  38  * this, we need to replace (for example) access like:
  39  *
  40  *    vec1 ssa_1 = intrinsic load_var () (gl_Fog.start) ()
  41  *
  42  * with:
  43  *
  44  *    vec4 ssa_2 = intrinsic load_var () (fog.params) ()
  45  *    vec1 ssa_1 = ssa_2.y
  46  *
  47  * with appropriate substitutions in the uniform variables list:
  48  *
  49  *    decl_var uniform INTERP_MODE_NONE gl_FogParameters gl_Fog (0, 0)
  50  *
  51  * would become:
  52  *
  53  *    decl_var uniform INTERP_MODE_NONE vec4 state.fog.color (0, 0)
  54  *    decl_var uniform INTERP_MODE_NONE vec4 state.fog.params (0, 1)
  55  *
  56  * See in particular 'struct gl_builtin_uniform_element'.
  57  */
  58
  59 #include "compiler/nir/nir.h"
  60 #include "compiler/nir/nir_builder.h"
  61 #include "st_nir.h"
  62 #include "compiler/glsl/ir.h"
  63 #include "uniforms.h"
  64 #include "program/prog_instruction.h"
  65
  66 typedef struct {
  67    nir_shader *shader;
  68    nir_builder builder;
  69    void *mem_ctx;
  70 } lower_builtin_state;
  71
  72 static const struct gl_builtin_uniform_element *
  73 get_element(const struct gl_builtin_uniform_desc *desc, nir_deref_var *deref)
  74 {
  75    nir_deref *tail = &deref->deref;
  76
  77    if ((desc->num_elements == 1) && (desc->elements[0].field == NULL))
  78       return NULL;
  79
  80    /* we handle arrays in get_variable(): */
  81    if (tail->child->deref_type == nir_deref_type_array)
  82       tail = tail->child;
  83
  84    /* don't need to deal w/ non-struct or array of non-struct: */
  85    if (!tail->child)
  86       return NULL;
  87
  88    if (tail->child->deref_type != nir_deref_type_struct)
  89       return NULL;
  90
  91    nir_deref_struct *deref_struct = nir_deref_as_struct(tail->child);
  92
  93    assert(deref_struct->index < desc->num_elements);
  94
  95    return &desc->elements[deref_struct->index];
  96 }
  97
  98 static nir_variable *
  99 get_variable(lower_builtin_state *state, nir_deref_var *deref,
 100              const struct gl_builtin_uniform_element *element)
 101 {
 102    nir_shader *shader = state->shader;
 103    int tokens[STATE_LENGTH];
 104
 105    memcpy(tokens, element->tokens, sizeof(tokens));
 106
 107    if (deref->deref.child->deref_type == nir_deref_type_array) {
 108       nir_deref_array *darr = nir_deref_as_array(deref->deref.child);
 109
 110       assert(darr->deref_array_type == nir_deref_array_type_direct);
 111
 112       /* we need to fixup the array index slot: */
 113       switch (tokens[0]) {
 114       case STATE_MODELVIEW_MATRIX:
 115       case STATE_PROJECTION_MATRIX:
 116       case STATE_MVP_MATRIX:
 117       case STATE_TEXTURE_MATRIX:
 118       case STATE_PROGRAM_MATRIX:
 119       case STATE_LIGHT:
 120       case STATE_LIGHTPROD:
 121       case STATE_TEXGEN:
 122       case STATE_TEXENV_COLOR:
 123       case STATE_CLIPPLANE:
 124          tokens[1] = darr->base_offset;
 125          break;
 126       }
 127    }
 128
 129    char *name = _mesa_program_state_string((gl_state_index *)tokens);
 130
 131    nir_foreach_variable(var, &shader->uniforms) {
 132       if (strcmp(var->name, name) == 0) {
 133          free(name);
 134          return var;
 135       }
 136    }
 137
 138    /* variable doesn't exist yet, so create it: */
 139    nir_variable *var =
 140       nir_variable_create(shader, nir_var_uniform, glsl_vec4_type(), name);
 141
 142    var->num_state_slots = 1;
 143    var->state_slots = ralloc_array(var, nir_state_slot, 1);
 144    memcpy(var->state_slots[0].tokens, tokens,
 145           sizeof(var->state_slots[0].tokens));
 146
 147    free(name);
 148
 149    return var;
 150 }
 151
 152 static bool
 153 lower_builtin_block(lower_builtin_state *state, nir_block *block)
 154 {
 155    nir_builder *b = &state->builder;
 156
 157    nir_foreach_instr_safe(instr, block) {
 158       if (instr->type != nir_instr_type_intrinsic)
 159          continue;
 160
 161       nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
 162
 163       if (intrin->intrinsic != nir_intrinsic_load_var)
 164          continue;
 165
 166       nir_variable *var = intrin->variables[0]->var;
 167       if (var->data.mode != nir_var_uniform)
 168          continue;
 169
 170       /* built-in's will always start with "gl_" */
 171       if (strncmp(var->name, "gl_", 3) != 0)
 172          continue;
 173
 174       const struct gl_builtin_uniform_desc *desc =
 175          _mesa_glsl_get_builtin_uniform_desc(var->name);
 176
 177       /* if no descriptor, it isn't something we need to handle specially: */
 178       if (!desc)
 179          continue;
 180
 181       const struct gl_builtin_uniform_element *element =
 182          get_element(desc, intrin->variables[0]);
 183
 184       /* matrix elements (array_deref) do not need special handling: */
 185       if (!element)
 186          continue;
 187
 188       /* remove existing var from uniform list: */
 189       exec_node_remove(&var->node);
 190       /* the _self_link() ensures we can remove multiple times, rather than
 191        * trying to keep track of what we have already removed:
 192        */
 193       exec_node_self_link(&var->node);
 194
 195       nir_variable *new_var =
 196          get_variable(state, intrin->variables[0], element);
 197
 198       b->cursor = nir_before_instr(instr);
 199
 200       nir_ssa_def *def = nir_load_var(b, new_var);
 201
 202       /* swizzle the result: */
 203       unsigned swiz[4];
 204       for (unsigned i = 0; i < 4; i++) {
 205          swiz[i] = GET_SWZ(element->swizzle, i);
 206          assert(swiz[i] <= SWIZZLE_W);
 207       }
 208       def = nir_swizzle(b, def, swiz, intrin->num_components, true);
 209
 210       /* and rewrite uses of original instruction: */
 211       assert(intrin->dest.is_ssa);
 212       nir_ssa_def_rewrite_uses(&intrin->dest.ssa, nir_src_for_ssa(def));
 213
 214       /* at this point intrin should be unused.  We need to remove it
 215        * (rather than waiting for DCE pass) to avoid dangling reference
 216        * to remove'd var.  And we have to remove the original uniform
 217        * var since we don't want it to get uniform space allocated.
 218        */
 219       exec_node_remove(&intrin->instr.node);
 220    }
 221
 222    return true;
 223 }
 224
 225 static void
 226 lower_builtin_impl(lower_builtin_state *state, nir_function_impl *impl)
 227 {
 228    nir_builder_init(&state->builder, impl);
 229    state->mem_ctx = ralloc_parent(impl);
 230
 231    nir_foreach_block(block, impl) {
 232       lower_builtin_block(state, block);
 233    }
 234
 235    nir_metadata_preserve(impl, nir_metadata_block_index |
 236                                nir_metadata_dominance);
 237 }
 238
 239 void
 240 st_nir_lower_builtin(nir_shader *shader)
 241 {
 242    lower_builtin_state state;
 243    state.shader = shader;
 244    nir_foreach_function(function, shader) {
 245       if (function->impl)
 246          lower_builtin_impl(&state, function->impl);
 247    }
 248 }