source/fuzz/transformation_adjust_branch_weights.cpp

   1 // Copyright (c) 2020 André Perez Maselco
   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/transformation_adjust_branch_weights.h"
  16
  17 #include "source/fuzz/fuzzer_util.h"
  18 #include "source/fuzz/instruction_descriptor.h"
  19
  20 namespace spvtools {
  21 namespace fuzz {
  22
  23 namespace {
  24
  25 const uint32_t kBranchWeightForTrueLabelIndex = 3;
  26 const uint32_t kBranchWeightForFalseLabelIndex = 4;
  27
  28 }  // namespace
  29
  30 TransformationAdjustBranchWeights::TransformationAdjustBranchWeights(
  31     protobufs::TransformationAdjustBranchWeights message)
  32     : message_(std::move(message)) {}
  33
  34 TransformationAdjustBranchWeights::TransformationAdjustBranchWeights(
  35     const protobufs::InstructionDescriptor& instruction_descriptor,
  36     const std::pair<uint32_t, uint32_t>& branch_weights) {
  37   *message_.mutable_instruction_descriptor() = instruction_descriptor;
  38   message_.mutable_branch_weights()->set_first(branch_weights.first);
  39   message_.mutable_branch_weights()->set_second(branch_weights.second);
  40 }
  41
  42 bool TransformationAdjustBranchWeights::IsApplicable(
  43     opt::IRContext* ir_context, const TransformationContext& /*unused*/) const {
  44   auto instruction =
  45       FindInstruction(message_.instruction_descriptor(), ir_context);
  46   if (instruction == nullptr) {
  47     return false;
  48   }
  49
  50   spv::Op opcode = static_cast<spv::Op>(
  51       message_.instruction_descriptor().target_instruction_opcode());
  52
  53   assert(instruction->opcode() == opcode &&
  54          "The located instruction must have the same opcode as in the "
  55          "descriptor.");
  56
  57   // Must be an OpBranchConditional instruction.
  58   if (opcode != spv::Op::OpBranchConditional) {
  59     return false;
  60   }
  61
  62   assert((message_.branch_weights().first() != 0 ||
  63           message_.branch_weights().second() != 0) &&
  64          "At least one weight must be non-zero.");
  65
  66   assert(message_.branch_weights().first() <=
  67              UINT32_MAX - message_.branch_weights().second() &&
  68          "The sum of the two weights must not be greater than UINT32_MAX.");
  69
  70   return true;
  71 }
  72
  73 void TransformationAdjustBranchWeights::Apply(
  74     opt::IRContext* ir_context, TransformationContext* /*unused*/) const {
  75   auto instruction =
  76       FindInstruction(message_.instruction_descriptor(), ir_context);
  77   if (instruction->HasBranchWeights()) {
  78     instruction->SetOperand(kBranchWeightForTrueLabelIndex,
  79                             {message_.branch_weights().first()});
  80     instruction->SetOperand(kBranchWeightForFalseLabelIndex,
  81                             {message_.branch_weights().second()});
  82   } else {
  83     instruction->AddOperand({SPV_OPERAND_TYPE_OPTIONAL_LITERAL_INTEGER,
  84                              {message_.branch_weights().first()}});
  85     instruction->AddOperand({SPV_OPERAND_TYPE_OPTIONAL_LITERAL_INTEGER,
  86                              {message_.branch_weights().second()}});
  87   }
  88 }
  89
  90 protobufs::Transformation TransformationAdjustBranchWeights::ToMessage() const {
  91   protobufs::Transformation result;
  92   *result.mutable_adjust_branch_weights() = message_;
  93   return result;
  94 }
  95
  96 std::unordered_set<uint32_t> TransformationAdjustBranchWeights::GetFreshIds()
  97     const {
  98   return std::unordered_set<uint32_t>();
  99 }
 100
 101 }  // namespace fuzz
 102 }  // namespace spvtools