Method GetInductionInitValue

source/opt/loop_descriptor.cpp:169–203

Extract the initial value from the |induction| OpPhi instruction and store it in |value|. If the function couldn't find the initial value of |induction| return false.

// in |value|. If the function couldn't find the initial value of |induction|
// return false.
bool Loop::GetInductionInitValue(const Instruction* induction,
                                 int64_t* value) const {
  Instruction* constant_instruction = nullptr;
  analysis::DefUseManager* def_use_manager = context_->get_def_use_mgr();

  for (uint32_t operand_id = 0; operand_id < induction->NumInOperands();
       operand_id += 2) {
    BasicBlock* bb = context_->cfg()->block(
        induction->GetSingleWordInOperand(operand_id + 1));

    if (!IsInsideLoop(bb)) {
      constant_instruction = def_use_manager->GetDef(
          induction->GetSingleWordInOperand(operand_id));
    }
  }

  if (!constant_instruction) return false;

  const analysis::Constant* constant =
      context_->get_constant_mgr()->FindDeclaredConstant(
          constant_instruction->result_id());
  if (!constant) return false;

  if (value) {
    const analysis::Integer* type = constant->type()->AsInteger();
    if (!type) {
      return false;
    }

    *value = type->IsSigned() ? constant->GetSignExtendedValue()
                              : constant->GetZeroExtendedValue();
  }

  return true;
}

Loop::Loop(IRContext* context, DominatorAnalysis* dom_analysis,
           BasicBlock* header, BasicBlock* continue_target,