Method CloseUnrolledLoop

source/opt/loop_unroller.cpp:805–846

}

void LoopUnrollerUtilsImpl::CloseUnrolledLoop(Loop* loop) {
  // Remove the OpLoopMerge instruction from the function.
  Instruction* merge_inst = loop->GetHeaderBlock()->GetLoopMergeInst();
  invalidated_instructions_.push_back(merge_inst);

  // Remove the final backedge to the header and make it point instead to the
  // merge block.
  Instruction* latch_instruction = state_.previous_latch_block_->terminator();
  latch_instruction->SetInOperand(0, {loop->GetMergeBlock()->id()});
  context_->UpdateDefUse(latch_instruction);

  // Remove all induction variables as the phis will now be invalid. Replace all
  // uses with the constant initializer value (all uses of phis will be in
  // the first iteration with the subsequent phis already having been removed).
  std::vector<Instruction*> inductions;
  loop->GetInductionVariables(inductions);

  // We can use the state instruction mechanism to replace all internal loop
  // values within the first loop trip (as the subsequent ones will be updated
  // by the copy function) with the value coming in from the preheader and then
  // use context ReplaceAllUsesWith for the uses outside the loop with the final
  // trip phi value.
  state_.new_inst.clear();
  for (Instruction* induction : inductions) {
    uint32_t initalizer_id =
        GetPhiDefID(induction, loop->GetPreHeaderBlock()->id());

    state_.new_inst[induction->result_id()] = initalizer_id;
  }

  for (BasicBlock* block : loop_blocks_inorder_) {
    RemapOperands(block);
  }
  for (auto& block_itr : blocks_to_add_) {
    RemapOperands(block_itr.get());
  }

  // Rewrite the last phis, since they may still reference the original phi.
  for (Instruction* last_phi : state_.previous_phis_) {
    RemapOperands(last_phi);
  }
}

// Uses the first loop to create a copy of the loop with new IDs.
bool LoopUnrollerUtilsImpl::DuplicateLoop(Loop* old_loop, Loop* new_loop) {