1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
|
// Copyright (c) 2019 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "source/fuzz/fuzzer_pass_add_dead_breaks.h"
#include "source/fuzz/transformation_add_dead_break.h"
#include "source/opt/ir_context.h"
namespace spvtools {
namespace fuzz {
FuzzerPassAddDeadBreaks::FuzzerPassAddDeadBreaks(
opt::IRContext* ir_context, FactManager* fact_manager,
FuzzerContext* fuzzer_context,
protobufs::TransformationSequence* transformations)
: FuzzerPass(ir_context, fact_manager, fuzzer_context, transformations) {}
FuzzerPassAddDeadBreaks::~FuzzerPassAddDeadBreaks() = default;
void FuzzerPassAddDeadBreaks::Apply() {
// We first collect up lots of possibly-applicable transformations.
std::vector<TransformationAddDeadBreak> candidate_transformations;
// We consider each function separately.
for (auto& function : *GetIRContext()->module()) {
// For a given function, we find all the merge blocks in that function.
std::vector<uint32_t> merge_block_ids;
for (auto& block : function) {
auto maybe_merge_id = block.MergeBlockIdIfAny();
if (maybe_merge_id) {
merge_block_ids.push_back(maybe_merge_id);
}
}
// We rather aggressively consider the possibility of adding a break from
// every block in the function to every merge block. Many of these will be
// inapplicable as they would be illegal. That's OK - we later discard the
// ones that turn out to be no good.
for (auto& block : function) {
for (auto merge_block_id : merge_block_ids) {
// TODO(https://github.com/KhronosGroup/SPIRV-Tools/issues/2856): right
// now we completely ignore OpPhi instructions at merge blocks. This
// will lead to interesting opportunities being missed.
auto candidate_transformation = TransformationAddDeadBreak(
block.id(), merge_block_id, GetFuzzerContext()->ChooseEven(), {});
if (candidate_transformation.IsApplicable(GetIRContext(),
*GetFactManager())) {
// Only consider a transformation as a candidate if it is applicable.
candidate_transformations.push_back(
std::move(candidate_transformation));
}
}
}
}
// Go through the candidate transformations that were accumulated,
// probabilistically deciding whether to consider each one further and
// applying the still-applicable ones that are considered further.
//
// We iterate through the candidate transformations in a random order by
// repeatedly removing a random candidate transformation from the sequence
// until no candidate transformations remain. This is done because
// transformations can potentially disable one another, so that iterating
// through them in order would lead to a higher probability of
// transformations appearing early in the sequence being applied compared
// with later transformations.
while (!candidate_transformations.empty()) {
// Choose a random index into the sequence of remaining candidate
// transformations.
auto index = GetFuzzerContext()->RandomIndex(candidate_transformations);
// Remove the transformation at the chosen index from the sequence.
auto transformation = std::move(candidate_transformations[index]);
candidate_transformations.erase(candidate_transformations.begin() + index);
// Probabilistically decide whether to try to apply it vs. ignore it, in the
// case that it is applicable.
if (transformation.IsApplicable(GetIRContext(), *GetFactManager()) &&
GetFuzzerContext()->ChoosePercentage(
GetFuzzerContext()->GetChanceOfAddingDeadBreak())) {
transformation.Apply(GetIRContext(), GetFactManager());
*GetTransformations()->add_transformation() = transformation.ToMessage();
}
}
}
} // namespace fuzz
} // namespace spvtools
|
