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 /*
25 * Implements a pass that lowers output and/or input variables to a
26 * temporary plus an output variable with a single copy at each exit
27 * point of the shader and/or an input variable with a single copy
28 * at the entrance point of the shader. This way the output variable
29 * is only ever written once and/or input is only read once, and there
30 * are no indirect outut/input accesses.
31 */
32
33 #include "nir.h"
34
35 struct lower_io_state {
36 nir_shader *shader;
37 nir_function_impl *entrypoint;
38 struct exec_list old_outputs;
39 struct exec_list old_inputs;
40 };
41
42 static void
emit_copies(nir_cursor cursor,nir_shader * shader,struct exec_list * new_vars,struct exec_list * old_vars)43 emit_copies(nir_cursor cursor, nir_shader *shader, struct exec_list *new_vars,
44 struct exec_list *old_vars)
45 {
46 assert(exec_list_length(new_vars) == exec_list_length(old_vars));
47
48 foreach_two_lists(new_node, new_vars, old_node, old_vars) {
49 nir_variable *newv = exec_node_data(nir_variable, new_node, node);
50 nir_variable *temp = exec_node_data(nir_variable, old_node, node);
51
52 /* No need to copy the contents of a non-fb_fetch_output output variable
53 * to the temporary allocated for it, since its initial value is
54 * undefined.
55 */
56 if (temp->data.mode == nir_var_shader_out &&
57 !temp->data.fb_fetch_output)
58 continue;
59
60 /* Can't copy the contents of the temporary back to a read-only
61 * interface variable. The value of the temporary won't have been
62 * modified by the shader anyway.
63 */
64 if (newv->data.read_only)
65 continue;
66
67 nir_intrinsic_instr *copy =
68 nir_intrinsic_instr_create(shader, nir_intrinsic_copy_var);
69 copy->variables[0] = nir_deref_var_create(copy, newv);
70 copy->variables[1] = nir_deref_var_create(copy, temp);
71
72 nir_instr_insert(cursor, ©->instr);
73 }
74 }
75
76 static void
emit_output_copies_impl(struct lower_io_state * state,nir_function_impl * impl)77 emit_output_copies_impl(struct lower_io_state *state, nir_function_impl *impl)
78 {
79 if (state->shader->info.stage == MESA_SHADER_GEOMETRY) {
80 /* For geometry shaders, we have to emit the output copies right
81 * before each EmitVertex call.
82 */
83 nir_foreach_block(block, impl) {
84 nir_foreach_instr(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_emit_vertex) {
90 nir_cursor cursor = nir_before_instr(&intrin->instr);
91 emit_copies(cursor, state->shader, &state->shader->outputs,
92 &state->old_outputs);
93 }
94 }
95 }
96 } else if (impl == state->entrypoint) {
97 nir_cursor cursor = nir_before_block(nir_start_block(impl));
98 emit_copies(cursor, state->shader, &state->old_outputs,
99 &state->shader->outputs);
100
101 /* For all other shader types, we need to do the copies right before
102 * the jumps to the end block.
103 */
104 struct set_entry *block_entry;
105 set_foreach(impl->end_block->predecessors, block_entry) {
106 struct nir_block *block = (void *)block_entry->key;
107 nir_cursor cursor = nir_after_block_before_jump(block);
108 emit_copies(cursor, state->shader, &state->shader->outputs,
109 &state->old_outputs);
110 }
111 }
112 }
113
114 static void
emit_input_copies_impl(struct lower_io_state * state,nir_function_impl * impl)115 emit_input_copies_impl(struct lower_io_state *state, nir_function_impl *impl)
116 {
117 if (impl == state->entrypoint) {
118 nir_cursor cursor = nir_before_block(nir_start_block(impl));
119 emit_copies(cursor, state->shader, &state->old_inputs,
120 &state->shader->inputs);
121 }
122 }
123
124 static nir_variable *
create_shadow_temp(struct lower_io_state * state,nir_variable * var)125 create_shadow_temp(struct lower_io_state *state, nir_variable *var)
126 {
127 nir_variable *nvar = ralloc(state->shader, nir_variable);
128 memcpy(nvar, var, sizeof *nvar);
129
130 /* The original is now the temporary */
131 nir_variable *temp = var;
132
133 /* Reparent the name to the new variable */
134 ralloc_steal(nvar, nvar->name);
135
136 assert(nvar->constant_initializer == NULL);
137
138 /* Give the original a new name with @<mode>-temp appended */
139 const char *mode = (temp->data.mode == nir_var_shader_in) ? "in" : "out";
140 temp->name = ralloc_asprintf(var, "%s@%s-temp", mode, nvar->name);
141 temp->data.mode = nir_var_global;
142 temp->data.read_only = false;
143 temp->data.fb_fetch_output = false;
144 temp->data.compact = false;
145
146 return nvar;
147 }
148
149 void
nir_lower_io_to_temporaries(nir_shader * shader,nir_function_impl * entrypoint,bool outputs,bool inputs)150 nir_lower_io_to_temporaries(nir_shader *shader, nir_function_impl *entrypoint,
151 bool outputs, bool inputs)
152 {
153 struct lower_io_state state;
154
155 if (shader->info.stage == MESA_SHADER_TESS_CTRL)
156 return;
157
158 state.shader = shader;
159 state.entrypoint = entrypoint;
160
161 if (inputs)
162 exec_list_move_nodes_to(&shader->inputs, &state.old_inputs);
163 else
164 exec_list_make_empty(&state.old_inputs);
165
166 if (outputs)
167 exec_list_move_nodes_to(&shader->outputs, &state.old_outputs);
168 else
169 exec_list_make_empty(&state.old_outputs);
170
171 /* Walk over all of the outputs turn each output into a temporary and
172 * make a new variable for the actual output.
173 */
174 nir_foreach_variable(var, &state.old_outputs) {
175 nir_variable *output = create_shadow_temp(&state, var);
176 exec_list_push_tail(&shader->outputs, &output->node);
177 }
178
179 /* and same for inputs: */
180 nir_foreach_variable(var, &state.old_inputs) {
181 nir_variable *input = create_shadow_temp(&state, var);
182 exec_list_push_tail(&shader->inputs, &input->node);
183 }
184
185 nir_foreach_function(function, shader) {
186 if (function->impl == NULL)
187 continue;
188
189 if (inputs)
190 emit_input_copies_impl(&state, function->impl);
191
192 if (outputs)
193 emit_output_copies_impl(&state, function->impl);
194
195 nir_metadata_preserve(function->impl, nir_metadata_block_index |
196 nir_metadata_dominance);
197 }
198
199 exec_list_append(&shader->globals, &state.old_inputs);
200 exec_list_append(&shader->globals, &state.old_outputs);
201 }
202