2 * Copyright © 2012 Vincent Lejeune
3 * Copyright © 2012 Intel Corporation
5 * Permission is hereby granted, free of charge, to any person obtaining a
6 * copy of this software and associated documentation files (the "Software"),
7 * to deal in the Software without restriction, including without limitation
8 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
9 * and/or sell copies of the Software, and to permit persons to whom the
10 * Software is furnished to do so, subject to the following conditions:
12 * The above copyright notice and this permission notice (including the next
13 * paragraph) shall be included in all copies or substantial portions of the
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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22 * DEALINGS IN THE SOFTWARE.
26 #include "util/hash_table.h"
29 * \file lower_output_reads.cpp
31 * In GLSL, shader output variables (such as varyings) can be both read and
32 * written. However, on some hardware, reading an output register causes
35 * This pass creates temporary shadow copies of every (used) shader output,
36 * and replaces all accesses to use those instead. It also adds code to the
37 * main() function to copy the final values to the actual shader outputs.
42 class output_read_remover
: public ir_hierarchical_visitor
{
45 * A hash table mapping from the original ir_variable shader outputs
46 * (ir_var_shader_out mode) to the new temporaries to be used instead.
48 hash_table
*replacements
;
54 output_read_remover(unsigned stage
);
55 ~output_read_remover();
56 virtual ir_visitor_status
visit(class ir_dereference_variable
*);
57 virtual ir_visitor_status
visit_leave(class ir_emit_vertex
*);
58 virtual ir_visitor_status
visit_leave(class ir_return
*);
59 virtual ir_visitor_status
visit_leave(class ir_function_signature
*);
62 } /* anonymous namespace */
65 * Hash function for the output variables - computes the hash of the name.
66 * NOTE: We're using the name string to ensure that the hash doesn't depend
67 * on any random factors, otherwise the output_read_remover could produce
68 * the random order of the assignments.
70 * NOTE: If you want to reuse this function please take into account that
71 * generally the names of the variables are non-unique.
74 hash_table_var_hash(const void *key
)
76 const ir_variable
* var
= static_cast<const ir_variable
*>(key
);
77 return _mesa_key_hash_string(var
->name
);
80 output_read_remover::output_read_remover(unsigned stage
)
83 mem_ctx
= ralloc_context(NULL
);
84 replacements
= _mesa_hash_table_create(NULL
, hash_table_var_hash
,
85 _mesa_key_pointer_equal
);
88 output_read_remover::~output_read_remover()
90 _mesa_hash_table_destroy(replacements
, NULL
);
95 output_read_remover::visit(ir_dereference_variable
*ir
)
97 if (ir
->var
->data
.mode
!= ir_var_shader_out
)
98 return visit_continue
;
99 if (stage
== MESA_SHADER_TESS_CTRL
)
100 return visit_continue
;
102 hash_entry
*entry
= _mesa_hash_table_search(replacements
, ir
->var
);
103 ir_variable
*temp
= entry
? (ir_variable
*) entry
->data
: NULL
;
105 /* If we don't have an existing temporary, create one. */
107 void *var_ctx
= ralloc_parent(ir
->var
);
108 temp
= new(var_ctx
) ir_variable(ir
->var
->type
, ir
->var
->name
,
110 _mesa_hash_table_insert(replacements
, ir
->var
, temp
);
111 ir
->var
->insert_after(temp
);
114 /* Update the dereference to use the temporary */
117 return visit_continue
;
121 * Create an assignment to copy a temporary value back to the actual output.
123 static ir_assignment
*
124 copy(void *ctx
, ir_variable
*output
, ir_variable
*temp
)
126 ir_dereference_variable
*lhs
= new(ctx
) ir_dereference_variable(output
);
127 ir_dereference_variable
*rhs
= new(ctx
) ir_dereference_variable(temp
);
128 return new(ctx
) ir_assignment(lhs
, rhs
);
131 /** Insert a copy-back assignment before a "return" statement or a call to
135 emit_return_copy(const void *key
, void *data
, void *closure
)
137 ir_return
*ir
= (ir_return
*) closure
;
138 ir
->insert_before(copy(ir
, (ir_variable
*) key
, (ir_variable
*) data
));
141 /** Insert a copy-back assignment at the end of the main() function */
143 emit_main_copy(const void *key
, void *data
, void *closure
)
145 ir_function_signature
*sig
= (ir_function_signature
*) closure
;
146 sig
->body
.push_tail(copy(sig
, (ir_variable
*) key
, (ir_variable
*) data
));
150 output_read_remover::visit_leave(ir_return
*ir
)
152 hash_table_call_foreach(replacements
, emit_return_copy
, ir
);
153 return visit_continue
;
157 output_read_remover::visit_leave(ir_emit_vertex
*ir
)
159 hash_table_call_foreach(replacements
, emit_return_copy
, ir
);
160 _mesa_hash_table_clear(replacements
, NULL
);
161 return visit_continue
;
165 output_read_remover::visit_leave(ir_function_signature
*sig
)
167 if (strcmp(sig
->function_name(), "main") != 0)
168 return visit_continue
;
170 hash_table_call_foreach(replacements
, emit_main_copy
, sig
);
171 return visit_continue
;
175 lower_output_reads(unsigned stage
, exec_list
*instructions
)
177 output_read_remover
v(stage
);
178 visit_list_elements(&v
, instructions
);