nir_propagate_invariant.c revision 01e04c3f 
1/*
2 * Copyright © 2016 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
21 * DEALINGS IN THE SOFTWARE.
22 */
23
24#include "nir.h"
25
26static void
27add_src(nir_src *src, struct set *invariants)
28{
29   if (src->is_ssa) {
30      _mesa_set_add(invariants, src->ssa);
31   } else {
32      _mesa_set_add(invariants, src->reg.reg);
33   }
34}
35
36static bool
37add_src_cb(nir_src *src, void *state)
38{
39   add_src(src, state);
40   return true;
41}
42
43static bool
44dest_is_invariant(nir_dest *dest, struct set *invariants)
45{
46   if (dest->is_ssa) {
47      return _mesa_set_search(invariants, &dest->ssa);
48   } else {
49      return _mesa_set_search(invariants, dest->reg.reg);
50   }
51}
52
53static void
54add_cf_node(nir_cf_node *cf, struct set *invariants)
55{
56   if (cf->type == nir_cf_node_if) {
57      nir_if *if_stmt = nir_cf_node_as_if(cf);
58      add_src(&if_stmt->condition, invariants);
59   }
60
61   if (cf->parent)
62      add_cf_node(cf->parent, invariants);
63}
64
65static void
66add_var(nir_variable *var, struct set *invariants)
67{
68   _mesa_set_add(invariants, var);
69}
70
71static bool
72var_is_invariant(nir_variable *var, struct set * invariants)
73{
74   return var->data.invariant || _mesa_set_search(invariants, var);
75}
76
77static void
78propagate_invariant_instr(nir_instr *instr, struct set *invariants)
79{
80   switch (instr->type) {
81   case nir_instr_type_alu: {
82      nir_alu_instr *alu = nir_instr_as_alu(instr);
83      if (!dest_is_invariant(&alu->dest.dest, invariants))
84         break;
85
86      alu->exact = true;
87      nir_foreach_src(instr, add_src_cb, invariants);
88      break;
89   }
90
91   case nir_instr_type_tex: {
92      nir_tex_instr *tex = nir_instr_as_tex(instr);
93      if (dest_is_invariant(&tex->dest, invariants))
94         nir_foreach_src(instr, add_src_cb, invariants);
95      break;
96   }
97
98   case nir_instr_type_intrinsic: {
99      nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
100      switch (intrin->intrinsic) {
101      case nir_intrinsic_copy_deref:
102         /* If the destination is invariant then so is the source */
103         if (var_is_invariant(nir_intrinsic_get_var(intrin, 0), invariants))
104            add_var(nir_intrinsic_get_var(intrin, 1), invariants);
105         break;
106
107      case nir_intrinsic_load_deref:
108         if (dest_is_invariant(&intrin->dest, invariants))
109            add_var(nir_intrinsic_get_var(intrin, 0), invariants);
110         break;
111
112      case nir_intrinsic_store_deref:
113         if (var_is_invariant(nir_intrinsic_get_var(intrin, 0), invariants))
114            add_src(&intrin->src[1], invariants);
115         break;
116
117      default:
118         /* Nothing to do */
119         break;
120      }
121   }
122
123   case nir_instr_type_deref:
124   case nir_instr_type_jump:
125   case nir_instr_type_ssa_undef:
126   case nir_instr_type_load_const:
127      break; /* Nothing to do */
128
129   case nir_instr_type_phi: {
130      nir_phi_instr *phi = nir_instr_as_phi(instr);
131      if (!dest_is_invariant(&phi->dest, invariants))
132         break;
133
134      nir_foreach_phi_src(src, phi) {
135         add_src(&src->src, invariants);
136         add_cf_node(&src->pred->cf_node, invariants);
137      }
138      break;
139   }
140
141   case nir_instr_type_call:
142      unreachable("This pass must be run after function inlining");
143
144   case nir_instr_type_parallel_copy:
145   default:
146      unreachable("Cannot have this instruction type");
147   }
148}
149
150static bool
151propagate_invariant_impl(nir_function_impl *impl, struct set *invariants)
152{
153   bool progress = false;
154
155   while (true) {
156      uint32_t prev_entries = invariants->entries;
157
158      nir_foreach_block_reverse(block, impl) {
159         nir_foreach_instr_reverse(instr, block)
160            propagate_invariant_instr(instr, invariants);
161      }
162
163      /* Keep running until we make no more progress. */
164      if (invariants->entries > prev_entries) {
165         progress = true;
166         continue;
167      } else {
168         break;
169      }
170   }
171
172   if (progress) {
173      nir_metadata_preserve(impl, nir_metadata_block_index |
174                                  nir_metadata_dominance |
175                                  nir_metadata_live_ssa_defs);
176   }
177
178   return progress;
179}
180
181bool
182nir_propagate_invariant(nir_shader *shader)
183{
184   /* Hash set of invariant things */
185   struct set *invariants = _mesa_set_create(NULL, _mesa_hash_pointer,
186                                             _mesa_key_pointer_equal);
187
188   bool progress = false;
189   nir_foreach_function(function, shader) {
190      if (function->impl && propagate_invariant_impl(function->impl, invariants))
191         progress = true;
192   }
193
194   _mesa_set_destroy(invariants, NULL);
195
196   return progress;
197}
198