1/*
2 * Copyright © 2021 Igalia S.L.
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#include "nir.h"
25#include "nir_builder.h"
26
27/* Some hardware doesn't have a way to check if invocation was demoted,
28 * in such case we have to track it ourselves.
29 * OpIsHelperInvocationEXT is specified as:
30 *
31 *  "An invocation is currently a helper invocation if it was originally
32 *   invoked as a helper invocation or if it has been demoted to a helper
33 *   invocation by OpDemoteToHelperInvocationEXT."
34 *
35 * Therefore we:
36 * - Set gl_IsHelperInvocationEXT = gl_HelperInvocation
37 * - Add "gl_IsHelperInvocationEXT = true" right before each demote
38 * - Add "gl_IsHelperInvocationEXT = gl_IsHelperInvocationEXT || condition"
39 *   right before each demote_if
40 */
41
42static bool
43nir_lower_load_and_store_is_helper(nir_builder *b, nir_instr *instr, void *data)
44{
45   if (instr->type != nir_instr_type_intrinsic)
46      return false;
47
48   nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
49   nir_deref_instr *is_helper_deref = (nir_deref_instr*) data;
50
51   switch (intrin->intrinsic) {
52   case nir_intrinsic_demote: {
53      b->cursor = nir_before_instr(instr);
54      nir_store_deref(b, is_helper_deref, nir_imm_bool(b, true), 1);
55      return true;
56   }
57   case nir_intrinsic_demote_if: {
58      b->cursor = nir_before_instr(instr);
59      nir_ssa_def *current_is_helper = nir_load_deref(b, is_helper_deref);
60      nir_ssa_def *updated_is_helper = nir_ior(b, current_is_helper, intrin->src[0].ssa);
61      nir_store_deref(b, is_helper_deref, updated_is_helper, 1);
62      return true;
63   }
64   case nir_intrinsic_is_helper_invocation: {
65      b->cursor = nir_before_instr(instr);
66      nir_ssa_def *is_helper = nir_load_deref(b, is_helper_deref);
67      nir_ssa_def_rewrite_uses(&intrin->dest.ssa, is_helper);
68      nir_instr_remove_v(instr);
69      return true;
70   }
71   default:
72      return false;
73   }
74}
75
76static bool
77has_is_helper_invocation(nir_shader *shader)
78{
79   nir_foreach_function(function, shader) {
80      if (!function->impl)
81         continue;
82
83      nir_foreach_block_safe(block, function->impl) {
84         nir_foreach_instr_safe(instr, block) {
85            if (instr->type != nir_instr_type_intrinsic)
86               continue;
87
88            nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
89            if (intrin->intrinsic == nir_intrinsic_is_helper_invocation)
90               return true;
91         }
92      }
93   }
94
95   return false;
96}
97
98bool
99nir_lower_is_helper_invocation(nir_shader *shader)
100{
101   if (shader->info.stage != MESA_SHADER_FRAGMENT)
102      return false;
103
104   if (!has_is_helper_invocation(shader))
105      return false;
106
107   nir_function_impl *entrypoint = nir_shader_get_entrypoint(shader);
108
109   nir_builder b;
110   nir_builder_init(&b, entrypoint);
111   b.cursor = nir_before_cf_list(&entrypoint->body);
112
113   nir_variable *is_helper = nir_local_variable_create(entrypoint,
114                                          glsl_bool_type(),
115                                          "gl_IsHelperInvocationEXT");
116
117   nir_ssa_def *started_as_helper = nir_load_helper_invocation(&b, 32);
118
119   nir_deref_instr *is_helper_deref = nir_build_deref_var(&b, is_helper);
120   nir_store_deref(&b, is_helper_deref, started_as_helper, 1);
121
122   return nir_shader_instructions_pass(shader,
123                                       nir_lower_load_and_store_is_helper,
124                                       nir_metadata_all,
125                                       is_helper_deref);
126}
127