2 * Copyright (C) 2019 Collabora, Ltd.
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:
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
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
23 * Authors (Collabora):
24 * Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
30 * Flushes undefined SSA values to a zero vector fo the appropriate component
31 * count, to avoid undefined behaviour in the resulting shader. Not required
32 * for conformance as use of uninitialized variables is explicitly left
33 * undefined by the spec. Works around buggy apps, however.
35 * Call immediately after nir_opt_undef. If called before, larger optimization
36 * opportunities from the former pass will be missed. If called outside of an
37 * optimization loop, constant propagation and algebraic optimizations won't be
38 * able to kick in to reduce stuff consuming the zero.
41 #include "compiler/nir/nir.h"
42 #include "compiler/nir/nir_builder.h"
44 bool nir_undef_to_zero(nir_shader
*shader
);
47 nir_undef_to_zero(nir_shader
*shader
)
49 bool progress
= false;
51 nir_foreach_function(function
, shader
) {
52 if (!function
->impl
) continue;
55 nir_builder_init(&b
, function
->impl
);
57 nir_foreach_block(block
, function
->impl
) {
58 nir_foreach_instr_safe(instr
, block
) {
59 if (instr
->type
!= nir_instr_type_ssa_undef
) continue;
61 nir_ssa_undef_instr
*und
= nir_instr_as_ssa_undef(instr
);
63 /* Get the required size */
64 unsigned c
= und
->def
.num_components
;
65 unsigned s
= und
->def
.bit_size
;
67 nir_const_value v
[NIR_MAX_VEC_COMPONENTS
];
68 memset(v
, 0, sizeof(v
));
70 b
.cursor
= nir_before_instr(instr
);
71 nir_ssa_def
*zero
= nir_build_imm(&b
, c
, s
, v
);
72 nir_src zerosrc
= nir_src_for_ssa(zero
);
74 nir_ssa_def_rewrite_uses(&und
->def
, zerosrc
);
80 nir_metadata_preserve(function
->impl
, nir_metadata_block_index
| nir_metadata_dominance
);