aboutsummaryrefslogtreecommitdiff
path: root/mesalib/src/glsl/lower_packed_varyings.cpp
blob: 09c551c4e63151c745aa111da08694c3da15a2e6 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
/*
 * Copyright © 2011 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 */

/**
 * \file lower_varyings_to_packed.cpp
 *
 * This lowering pass generates GLSL code that manually packs varyings into
 * vec4 slots, for the benefit of back-ends that don't support packed varyings
 * natively.
 *
 * For example, the following shader:
 *
 *   out mat3x2 foo;  // location=4, location_frac=0
 *   out vec3 bar[2]; // location=5, location_frac=2
 *
 *   main()
 *   {
 *     ...
 *   }
 *
 * Is rewritten to:
 *
 *   mat3x2 foo;
 *   vec3 bar[2];
 *   out vec4 packed4; // location=4, location_frac=0
 *   out vec4 packed5; // location=5, location_frac=0
 *   out vec4 packed6; // location=6, location_frac=0
 *
 *   main()
 *   {
 *     ...
 *     packed4.xy = foo[0];
 *     packed4.zw = foo[1];
 *     packed5.xy = foo[2];
 *     packed5.zw = bar[0].xy;
 *     packed6.x = bar[0].z;
 *     packed6.yzw = bar[1];
 *   }
 *
 * This lowering pass properly handles "double parking" of a varying vector
 * across two varying slots.  For example, in the code above, two of the
 * components of bar[0] are stored in packed5, and the remaining component is
 * stored in packed6.
 *
 * Note that in theory, the extra instructions may cause some loss of
 * performance.  However, hopefully in most cases the performance loss will
 * either be absorbed by a later optimization pass, or it will be offset by
 * memory bandwidth savings (because fewer varyings are used).
 */

#include "glsl_symbol_table.h"
#include "ir.h"
#include "ir_optimization.h"

/**
 * Visitor that performs varying packing.  For each varying declared in the
 * shader, this visitor determines whether it needs to be packed.  If so, it
 * demotes it to an ordinary global, creates new packed varyings, and
 * generates assignments to convert between the original varying and the
 * packed varying.
 */
class lower_packed_varyings_visitor
{
public:
   lower_packed_varyings_visitor(void *mem_ctx, unsigned location_base,
                                 unsigned locations_used,
                                 ir_variable_mode mode,
                                 exec_list *main_instructions);

   void run(exec_list *instructions);

private:
   unsigned lower_rvalue(ir_rvalue *rvalue, unsigned fine_location,
                         ir_variable *unpacked_var, const char *name);
   unsigned lower_arraylike(ir_rvalue *rvalue, unsigned array_size,
                            unsigned fine_location,
                            ir_variable *unpacked_var, const char *name);
   ir_variable *get_packed_varying(unsigned location,
                                   ir_variable *unpacked_var,
                                   const char *name);
   bool needs_lowering(ir_variable *var);

   /**
    * Memory context used to allocate new instructions for the shader.
    */
   void * const mem_ctx;

   /**
    * Location representing the first generic varying slot for this shader
    * stage (e.g. VERT_RESULT_VAR0 if we are packing vertex shader outputs).
    * Varyings whose location is less than this value are assumed to
    * correspond to special fixed function hardware, so they are not lowered.
    */
   const unsigned location_base;

   /**
    * Number of generic varying slots which are used by this shader.  This is
    * used to allocate temporary intermediate data structures.  If any any
    * varying used by this shader has a location greater than or equal to
    * location_base + locations_used, an assertion will fire.
    */
   const unsigned locations_used;

   /**
    * Array of pointers to the packed varyings that have been created for each
    * generic varying slot.  NULL entries in this array indicate varying slots
    * for which a packed varying has not been created yet.
    */
   ir_variable **packed_varyings;

   /**
    * Type of varying which is being lowered in this pass (either ir_var_in or
    * ir_var_out).
    */
   const ir_variable_mode mode;

   /**
    * List of instructions corresponding to the main() function.  This is
    * where we add instructions to pack or unpack the varyings.
    */
   exec_list *main_instructions;
};

lower_packed_varyings_visitor::lower_packed_varyings_visitor(
      void *mem_ctx, unsigned location_base, unsigned locations_used,
      ir_variable_mode mode, exec_list *main_instructions)
   : mem_ctx(mem_ctx),
     location_base(location_base),
     locations_used(locations_used),
     packed_varyings((ir_variable **)
                     rzalloc_array_size(mem_ctx, sizeof(*packed_varyings),
                                        locations_used)),
     mode(mode),
     main_instructions(main_instructions)
{
}

void
lower_packed_varyings_visitor::run(exec_list *instructions)
{
   foreach_list (node, instructions) {
      ir_variable *var = ((ir_instruction *) node)->as_variable();
      if (var == NULL)
         continue;

      if (var->mode != this->mode ||
          var->location < (int) this->location_base ||
          !this->needs_lowering(var))
         continue;

      /* Change the old varying into an ordinary global. */
      var->mode = ir_var_auto;

      /* Create a reference to the old varying. */
      ir_dereference_variable *deref
         = new(this->mem_ctx) ir_dereference_variable(var);

      /* Recursively pack or unpack it. */
      this->lower_rvalue(deref, var->location * 4 + var->location_frac, var,
                         var->name);
   }
}

/**
 * Recursively pack or unpack the given varying (or portion of a varying) by
 * traversing all of its constituent vectors.
 *
 * \param fine_location is the location where the first constituent vector
 * should be packed--the word "fine" indicates that this location is expressed
 * in multiples of a float, rather than multiples of a vec4 as is used
 * elsewhere in Mesa.
 *
 * \return the location where the next constituent vector (after this one)
 * should be packed.
 */
unsigned
lower_packed_varyings_visitor::lower_rvalue(ir_rvalue *rvalue,
                                            unsigned fine_location,
                                            ir_variable *unpacked_var,
                                            const char *name)
{
   /* FINISHME: Support for "varying" records in GLSL 1.50. */
   assert(!rvalue->type->is_record());

   if (rvalue->type->is_array()) {
      /* Arrays are packed/unpacked by considering each array element in
       * sequence.
       */
      return this->lower_arraylike(rvalue, rvalue->type->array_size(),
                                   fine_location, unpacked_var, name);
   } else if (rvalue->type->is_matrix()) {
      /* Matrices are packed/unpacked by considering each column vector in
       * sequence.
       */
      return this->lower_arraylike(rvalue, rvalue->type->matrix_columns,
                                   fine_location, unpacked_var, name);
   } else if (rvalue->type->vector_elements + fine_location % 4 > 4) {
      /* This vector is going to be "double parked" across two varying slots,
       * so handle it as two separate assignments.
       */
      unsigned left_components = 4 - fine_location % 4;
      unsigned right_components
         = rvalue->type->vector_elements - left_components;
      unsigned left_swizzle_values[4] = { 0, 0, 0, 0 };
      unsigned right_swizzle_values[4] = { 0, 0, 0, 0 };
      char left_swizzle_name[4] = { 0, 0, 0, 0 };
      char right_swizzle_name[4] = { 0, 0, 0, 0 };
      for (unsigned i = 0; i < left_components; i++) {
         left_swizzle_values[i] = i;
         left_swizzle_name[i] = "xyzw"[i];
      }
      for (unsigned i = 0; i < right_components; i++) {
         right_swizzle_values[i] = i + left_components;
         right_swizzle_name[i] = "xyzw"[i + left_components];
      }
      ir_swizzle *left_swizzle = new(this->mem_ctx)
         ir_swizzle(rvalue, left_swizzle_values, left_components);
      ir_swizzle *right_swizzle = new(this->mem_ctx)
         ir_swizzle(rvalue->clone(this->mem_ctx, NULL), right_swizzle_values,
                    right_components);
      char *left_name
         = ralloc_asprintf(this->mem_ctx, "%s.%s", name, left_swizzle_name);
      char *right_name
         = ralloc_asprintf(this->mem_ctx, "%s.%s", name, right_swizzle_name);
      fine_location = this->lower_rvalue(left_swizzle, fine_location,
                                         unpacked_var, left_name);
      return this->lower_rvalue(right_swizzle, fine_location, unpacked_var,
                                right_name);
   } else {
      /* No special handling is necessary; pack the rvalue into the
       * varying.
       */
      unsigned swizzle_values[4] = { 0, 0, 0, 0 };
      unsigned components = rvalue->type->vector_elements;
      unsigned location = fine_location / 4;
      unsigned location_frac = fine_location % 4;
      for (unsigned i = 0; i < components; ++i)
         swizzle_values[i] = i + location_frac;
      ir_dereference_variable *packed_deref = new(this->mem_ctx)
         ir_dereference_variable(this->get_packed_varying(location,
                                                          unpacked_var, name));
      ir_swizzle *swizzle = new(this->mem_ctx)
         ir_swizzle(packed_deref, swizzle_values, components);
      if (this->mode == ir_var_out) {
         ir_assignment *assignment = new(this->mem_ctx)
            ir_assignment(swizzle, rvalue);
         this->main_instructions->push_tail(assignment);
      } else {
         ir_assignment *assignment = new(this->mem_ctx)
            ir_assignment(rvalue, swizzle);
         this->main_instructions->push_head(assignment);
      }
      return fine_location + components;
   }
}

/**
 * Recursively pack or unpack a varying for which we need to iterate over its
 * constituent elements, accessing each one using an ir_dereference_array.
 * This takes care of both arrays and matrices, since ir_dereference_array
 * treats a matrix like an array of its column vectors.
 */
unsigned
lower_packed_varyings_visitor::lower_arraylike(ir_rvalue *rvalue,
                                               unsigned array_size,
                                               unsigned fine_location,
                                               ir_variable *unpacked_var,
                                               const char *name)
{
   for (unsigned i = 0; i < array_size; i++) {
      if (i != 0)
         rvalue = rvalue->clone(this->mem_ctx, NULL);
      ir_constant *constant = new(this->mem_ctx) ir_constant(i);
      ir_dereference_array *dereference_array = new(this->mem_ctx)
         ir_dereference_array(rvalue, constant);
      char *subscripted_name
         = ralloc_asprintf(this->mem_ctx, "%s[%d]", name, i);
      fine_location = this->lower_rvalue(dereference_array, fine_location,
                                         unpacked_var, subscripted_name);
   }
   return fine_location;
}

/**
 * Retrieve the packed varying corresponding to the given varying location.
 * If no packed varying has been created for the given varying location yet,
 * create it and add it to the shader before returning it.
 *
 * The newly created varying inherits its base type (float, uint, or int) and
 * interpolation parameters from \c unpacked_var.
 */
ir_variable *
lower_packed_varyings_visitor::get_packed_varying(unsigned location,
                                                  ir_variable *unpacked_var,
                                                  const char *name)
{
   unsigned slot = location - this->location_base;
   assert(slot < locations_used);
   if (this->packed_varyings[slot] == NULL) {
      char *packed_name = ralloc_asprintf(this->mem_ctx, "packed:%s", name);
      const glsl_type *packed_type = glsl_type::get_instance(
            unpacked_var->type->get_scalar_type()->base_type, 4, 1);
      ir_variable *packed_var = new(this->mem_ctx)
         ir_variable(packed_type, packed_name, this->mode);
      packed_var->centroid = unpacked_var->centroid;
      packed_var->interpolation = unpacked_var->interpolation;
      packed_var->location = location;
      unpacked_var->insert_before(packed_var);
      this->packed_varyings[slot] = packed_var;
   } else {
      ralloc_asprintf_append((char **) &this->packed_varyings[slot]->name,
                             ",%s", name);
   }
   return this->packed_varyings[slot];
}

bool
lower_packed_varyings_visitor::needs_lowering(ir_variable *var)
{
   /* Things composed of vec4's don't need lowering.  Everything else does. */
   const glsl_type *type = var->type;
   if (type->is_array())
      type = type->fields.array;
   if (type->vector_elements == 4)
      return false;
   return true;
}

void
lower_packed_varyings(void *mem_ctx, unsigned location_base,
                      unsigned locations_used, ir_variable_mode mode,
                      gl_shader *shader)
{
   exec_list *instructions = shader->ir;
   ir_function *main_func = shader->symbols->get_function("main");
   exec_list void_parameters;
   ir_function_signature *main_func_sig
      = main_func->matching_signature(&void_parameters);
   exec_list *main_instructions = &main_func_sig->body;
   lower_packed_varyings_visitor visitor(mem_ctx, location_base,
                                         locations_used, mode,
                                         main_instructions);
   visitor.run(instructions);
}