Method FindConditionBlock

source/opt/loop_descriptor.cpp:619–656

}

BasicBlock* Loop::FindConditionBlock() const {
  if (!loop_merge_) {
    return nullptr;
  }
  BasicBlock* condition_block = nullptr;

  uint32_t in_loop_pred = 0;
  for (uint32_t p : context_->cfg()->preds(loop_merge_->id())) {
    if (IsInsideLoop(p)) {
      if (in_loop_pred) {
        // 2 in-loop predecessors.
        return nullptr;
      }
      in_loop_pred = p;
    }
  }
  if (!in_loop_pred) {
    // Merge block is unreachable.
    return nullptr;
  }

  BasicBlock* bb = context_->cfg()->block(in_loop_pred);

  if (!bb) return nullptr;

  const Instruction& branch = *bb->ctail();

  // Make sure the branch is a conditional branch.
  if (branch.opcode() != spv::Op::OpBranchConditional) return nullptr;

  // Make sure one of the two possible branches is to the merge block.
  if (branch.GetSingleWordInOperand(1) == loop_merge_->id() ||
      branch.GetSingleWordInOperand(2) == loop_merge_->id()) {
    condition_block = bb;
  }

  return condition_block;
}

bool Loop::FindNumberOfIterations(const Instruction* induction,
                                  const Instruction* branch_inst,