1 // Copyright (c) 2019 Google LLC
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 #include "source/fuzz/fuzzer_pass_adjust_loop_controls.h"
16
17 #include "source/fuzz/transformation_set_loop_control.h"
18
19 namespace spvtools {
20 namespace fuzz {
21
FuzzerPassAdjustLoopControls(opt::IRContext * ir_context,TransformationContext * transformation_context,FuzzerContext * fuzzer_context,protobufs::TransformationSequence * transformations)22 FuzzerPassAdjustLoopControls::FuzzerPassAdjustLoopControls(
23 opt::IRContext* ir_context, TransformationContext* transformation_context,
24 FuzzerContext* fuzzer_context,
25 protobufs::TransformationSequence* transformations)
26 : FuzzerPass(ir_context, transformation_context, fuzzer_context,
27 transformations) {}
28
29 FuzzerPassAdjustLoopControls::~FuzzerPassAdjustLoopControls() = default;
30
Apply()31 void FuzzerPassAdjustLoopControls::Apply() {
32 // Consider every merge instruction in the module (via looking through all
33 // functions and blocks).
34 for (auto& function : *GetIRContext()->module()) {
35 for (auto& block : function) {
36 if (auto merge_inst = block.GetMergeInst()) {
37 // Ignore the instruction if it is not a loop merge.
38 if (merge_inst->opcode() != SpvOpLoopMerge) {
39 continue;
40 }
41
42 // Decide randomly whether to adjust this loop merge.
43 if (!GetFuzzerContext()->ChoosePercentage(
44 GetFuzzerContext()->GetChanceOfAdjustingLoopControl())) {
45 continue;
46 }
47
48 uint32_t existing_mask = merge_inst->GetSingleWordOperand(
49 TransformationSetLoopControl::kLoopControlMaskInOperandIndex);
50
51 // First, set the new mask to one of None, Unroll or DontUnroll.
52 std::vector<uint32_t> basic_masks = {SpvLoopControlMaskNone,
53 SpvLoopControlUnrollMask,
54 SpvLoopControlDontUnrollMask};
55 uint32_t new_mask =
56 basic_masks[GetFuzzerContext()->RandomIndex(basic_masks)];
57
58 // For the loop controls that depend on guarantees about what the loop
59 // does, check which of these were present in the existing mask and
60 // randomly decide whether to keep them. They are just hints, so
61 // removing them should not change the semantics of the module.
62 for (auto mask_bit :
63 {SpvLoopControlDependencyInfiniteMask,
64 SpvLoopControlDependencyLengthMask,
65 SpvLoopControlMinIterationsMask, SpvLoopControlMaxIterationsMask,
66 SpvLoopControlIterationMultipleMask}) {
67 if ((existing_mask & mask_bit) && GetFuzzerContext()->ChooseEven()) {
68 // The mask bits we are considering are not available in all SPIR-V
69 // versions. However, we only include a mask bit if it was present
70 // in the original loop control mask, and we work under the
71 // assumption that we are transforming a valid module, thus we don't
72 // need to actually check whether the SPIR-V version being used
73 // supports these loop control mask bits.
74 new_mask |= mask_bit;
75 }
76 }
77
78 // We use 0 for peel count and partial count in the case that we choose
79 // not to set these controls.
80 uint32_t peel_count = 0;
81 uint32_t partial_count = 0;
82
83 // PeelCount and PartialCount are not compatible with DontUnroll, so
84 // we check whether DontUnroll is set.
85 if (!(new_mask & SpvLoopControlDontUnrollMask)) {
86 // If PeelCount is supported by this SPIR-V version, randomly choose
87 // whether to set it. If it was set in the original mask and is not
88 // selected for setting here, that amounts to dropping it.
89 if (TransformationSetLoopControl::PeelCountIsSupported(
90 GetIRContext()) &&
91 GetFuzzerContext()->ChooseEven()) {
92 new_mask |= SpvLoopControlPeelCountMask;
93 // The peel count is chosen randomly - if PeelCount was already set
94 // this will overwrite whatever peel count was previously used.
95 peel_count = GetFuzzerContext()->GetRandomLoopControlPeelCount();
96 }
97 // Similar, but for PartialCount.
98 if (TransformationSetLoopControl::PartialCountIsSupported(
99 GetIRContext()) &&
100 GetFuzzerContext()->ChooseEven()) {
101 new_mask |= SpvLoopControlPartialCountMask;
102 partial_count =
103 GetFuzzerContext()->GetRandomLoopControlPartialCount();
104 }
105 }
106
107 // Apply the transformation and add it to the output transformation
108 // sequence.
109 TransformationSetLoopControl transformation(block.id(), new_mask,
110 peel_count, partial_count);
111 ApplyTransformation(transformation);
112 }
113 }
114 }
115 }
116
117 } // namespace fuzz
118 } // namespace spvtools
119