bool InstructionFusion::IsExpensive()

in tensorflow/tensorflow/compiler/xla/service/instruction_fusion.cc [59:185]
115 lines of code
102 McCabe index (conditional complexity)

/*static*/ bool InstructionFusion::IsExpensive(
    const HloInstruction& instruction) {
  namespace m = match;

  switch (instruction.opcode()) {
    // Cheap instructions.
    case HloOpcode::kAdd:
    case HloOpcode::kAnd:
    case HloOpcode::kBitcast:
    case HloOpcode::kBitcastConvert:
    case HloOpcode::kBroadcast:
    case HloOpcode::kCeil:
    case HloOpcode::kClamp:
    case HloOpcode::kClz:
    case HloOpcode::kCompare:
    case HloOpcode::kComplex:
    case HloOpcode::kConcatenate:
    case HloOpcode::kConstant:
    case HloOpcode::kConvert:
    case HloOpcode::kCopy:
    case HloOpcode::kCopyDone:
    case HloOpcode::kCopyStart:
    case HloOpcode::kDynamicSlice:
    case HloOpcode::kDynamicUpdateSlice:
    case HloOpcode::kFloor:
    case HloOpcode::kGetTupleElement:
    case HloOpcode::kImag:
    case HloOpcode::kInfeed:
    case HloOpcode::kIota:
    case HloOpcode::kIsFinite:
    case HloOpcode::kMaximum:
    case HloOpcode::kMinimum:
    case HloOpcode::kMultiply:
    case HloOpcode::kNegate:
    case HloOpcode::kNot:
    case HloOpcode::kOr:
    case HloOpcode::kXor:
    case HloOpcode::kOutfeed:
    case HloOpcode::kPad:
    case HloOpcode::kPartitionId:
    case HloOpcode::kPopulationCount:
    case HloOpcode::kReal:
    case HloOpcode::kReducePrecision:
    case HloOpcode::kReplicaId:
    case HloOpcode::kReshape:
    case HloOpcode::kReverse:
    case HloOpcode::kRoundNearestAfz:
    case HloOpcode::kSelect:
    case HloOpcode::kShiftLeft:
    case HloOpcode::kShiftRightArithmetic:
    case HloOpcode::kShiftRightLogical:
    case HloOpcode::kSlice:
    case HloOpcode::kSubtract:
    case HloOpcode::kTranspose:
    case HloOpcode::kTuple:
    case HloOpcode::kTupleSelect:
      return false;

    // Cheap instructions for reals, but expensive for complex.
    case HloOpcode::kAbs:
    case HloOpcode::kCos:
    case HloOpcode::kSign:
    case HloOpcode::kSin:
      return ShapeUtil::ElementIsComplex(instruction.shape());

    // We say that integer div/mod by a constant is cheap because it gets
    // compiled down to multiplies and shifts, and we consider those to be
    // cheap.
    case HloOpcode::kDivide:
    case HloOpcode::kRemainder:
      return !ShapeUtil::ElementIsIntegral(instruction.shape()) ||
             !Match(instruction.operand(1),
                    m::AnyOf<const HloInstruction>(
                        m::ConstantEffectiveScalar(),
                        m::Broadcast(m::ConstantEffectiveScalar())));

    // Expensive instructions or unusual instructions for which fusion is
    // nonsensical.
    case HloOpcode::kAddDependency:
    case HloOpcode::kAfterAll:
    case HloOpcode::kAtan2:
    case HloOpcode::kBatchNormGrad:
    case HloOpcode::kBatchNormInference:
    case HloOpcode::kBatchNormTraining:
    case HloOpcode::kCall:
    case HloOpcode::kCholesky:
    case HloOpcode::kConditional:
    case HloOpcode::kConvolution:
    case HloOpcode::kAllReduce:
    case HloOpcode::kAllToAll:
    case HloOpcode::kCollectivePermute:
    case HloOpcode::kCustomCall:
    case HloOpcode::kDomain:
    case HloOpcode::kDot:
    case HloOpcode::kExp:
    case HloOpcode::kExpm1:
    case HloOpcode::kFft:
    case HloOpcode::kFusion:
    case HloOpcode::kGather:
    case HloOpcode::kLog:
    case HloOpcode::kLog1p:
    case HloOpcode::kMap:
    case HloOpcode::kParameter:
    case HloOpcode::kPower:
    case HloOpcode::kRecv:
    case HloOpcode::kRecvDone:
    case HloOpcode::kReduce:
    case HloOpcode::kReduceWindow:
    case HloOpcode::kRng:
    case HloOpcode::kRngGetAndUpdateState:
    case HloOpcode::kRsqrt:
    case HloOpcode::kScatter:
    case HloOpcode::kSelectAndScatter:
    case HloOpcode::kSend:
    case HloOpcode::kSendDone:
    case HloOpcode::kSort:
    case HloOpcode::kSqrt:
    case HloOpcode::kTanh:
    case HloOpcode::kTrace:
    case HloOpcode::kTriangularSolve:
    case HloOpcode::kWhile:
    case HloOpcode::kGetDimensionSize:
      return true;
  }

  return false;
}