aboutsummaryrefslogtreecommitdiffstats
path: root/src/compiler/nir/nir_split_var_copies.c
blob: 6260a8d7bfa534f0708e578e1ce768597d803ab5 (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
/*
 * Copyright © 2014 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.
 *
 * Authors:
 *    Jason Ekstrand (jason@jlekstrand.net)
 *
 */

#include "nir.h"
#include "nir_builder.h"

/*
 * Implements "copy splitting" which is similar to structure splitting only
 * it works on copy operations rather than the datatypes themselves.  The
 * GLSL language allows you to copy one variable to another an entire
 * structure (which may contain arrays or other structures) at a time.
 * Normally, in a language such as C this would be handled by a "structure
 * splitting" pass that breaks up the structures.  Unfortunately for us,
 * structures used in inputs or outputs can't be split.  Therefore,
 * regardlesss of what we do, we have to be able to copy to/from
 * structures.
 *
 * The primary purpose of structure splitting is to allow you to better
 * optimize variable access and lower things to registers where you can.
 * The primary issue here is that, if you lower the copy to a bunch of
 * loads and stores, you loose a lot of information about the copy
 * operation that you would like to keep around.  To solve this problem, we
 * have a "copy splitting" pass that, instead of splitting the structures
 * or lowering the copy into loads and storres, splits the copy operation
 * into a bunch of copy operations one for each leaf of the structure tree.
 * If an intermediate array is encountered, it is referenced with a
 * wildcard reference to indicate that the entire array is to be copied.
 *
 * As things become direct, array copies may be able to be losslessly
 * lowered to having fewer and fewer wildcards.  However, until that
 * happens we want to keep the information about the arrays intact.
 *
 * Prior to the copy splitting pass, there are no wildcard references but
 * there may be incomplete references where the tail of the deref chain is
 * an array or a structure and not a specific element.  After the copy
 * splitting pass has completed, every variable deref will be a full-length
 * dereference pointing to a single leaf in the structure type tree with
 * possibly a few wildcard array dereferences.
 */

static void
split_deref_copy_instr(nir_builder *b,
                       nir_deref_instr *dst, nir_deref_instr *src)
{
   assert(dst->type == src->type);
   if (glsl_type_is_vector_or_scalar(src->type)) {
      nir_copy_deref(b, dst, src);
   } else if (glsl_type_is_struct(src->type)) {
      for (unsigned i = 0; i < glsl_get_length(src->type); i++) {
         split_deref_copy_instr(b, nir_build_deref_struct(b, dst, i),
                                   nir_build_deref_struct(b, src, i));
      }
   } else {
      assert(glsl_type_is_matrix(src->type) || glsl_type_is_array(src->type));
      split_deref_copy_instr(b, nir_build_deref_array_wildcard(b, dst),
                                nir_build_deref_array_wildcard(b, src));
   }
}

static bool
split_var_copies_impl(nir_function_impl *impl)
{
   bool progress = false;

   nir_builder b;
   nir_builder_init(&b, impl);

   nir_foreach_block(block, impl) {
      nir_foreach_instr_safe(instr, block) {
         if (instr->type != nir_instr_type_intrinsic)
            continue;

         nir_intrinsic_instr *copy = nir_instr_as_intrinsic(instr);
         if (copy->intrinsic != nir_intrinsic_copy_deref)
            continue;

         b.cursor = nir_instr_remove(&copy->instr);

         nir_deref_instr *dst =
            nir_instr_as_deref(copy->src[0].ssa->parent_instr);
         nir_deref_instr *src =
            nir_instr_as_deref(copy->src[1].ssa->parent_instr);
         split_deref_copy_instr(&b, dst, src);

         progress = true;
      }
   }

   if (progress) {
      nir_metadata_preserve(impl, nir_metadata_block_index |
                                  nir_metadata_dominance);
   } else {
#ifndef NDEBUG
      impl->valid_metadata &= ~nir_metadata_not_properly_reset;
#endif
   }

   return progress;
}

bool
nir_split_var_copies(nir_shader *shader)
{
   bool progress = false;

   nir_foreach_function(function, shader) {
      if (function->impl)
         progress = split_var_copies_impl(function->impl) || progress;
   }

   return progress;
}