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 "nir_builder.h"
26
27static nir_intrinsic_instr *
28as_intrinsic(nir_instr *instr, nir_intrinsic_op op)
29{
30   if (instr->type != nir_instr_type_intrinsic)
31      return NULL;
32
33   nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
34   if (intrin->intrinsic != op)
35      return NULL;
36
37   return intrin;
38}
39
40static nir_intrinsic_instr *
41as_set_vertex_count(nir_instr *instr)
42{
43   return as_intrinsic(instr, nir_intrinsic_set_vertex_count);
44}
45
46/**
47 * If a geometry shader emits a constant number of vertices, return the
48 * number of vertices.  Otherwise, return -1 (unknown).
49 *
50 * This only works if you've used nir_lower_gs_intrinsics() to do vertex
51 * counting at the NIR level.
52 */
53int
54nir_gs_count_vertices(const nir_shader *shader)
55{
56   int count = -1;
57
58   nir_foreach_function(function, shader) {
59      if (!function->impl)
60         continue;
61
62      /* set_vertex_count intrinsics only appear in predecessors of the
63       * end block.  So we don't need to walk all of them.
64       */
65      struct set_entry *entry;
66      set_foreach(function->impl->end_block->predecessors, entry) {
67         nir_block *block = (nir_block *) entry->key;
68
69         nir_foreach_instr_reverse(instr, block) {
70            nir_intrinsic_instr *intrin = as_set_vertex_count(instr);
71            if (!intrin)
72               continue;
73
74            nir_const_value *val = nir_src_as_const_value(intrin->src[0]);
75            /* We've found a non-constant value.  Bail. */
76            if (!val)
77               return -1;
78
79            if (count == -1)
80               count = val->i32[0];
81
82            /* We've found contradictory set_vertex_count intrinsics.
83             * This can happen if there are early-returns in main() and
84             * different paths emit different numbers of vertices.
85             */
86            if (count != val->i32[0])
87               return -1;
88         }
89      }
90   }
91
92   return count;
93}
94