Method RewriteUse

source/opt/loop_utils.cpp:71–89

Rewrites the use of |def_insn_| by the instruction |user| at the index |operand_index| in terms of phi instruction. This recursively builds new phi instructions from |user| to the loop exit blocks' phis. The use of |def_insn_| in |user| is replaced by the relevant phi instruction at the end of the operation. It is assumed that |user| does not dominates any of the loop exit basic block. This operat

    // records what needs to be updated. The actual update is performed by
    // UpdateManagers.
    bool RewriteUse(BasicBlock* bb, Instruction* user, uint32_t operand_index) {
      assert(
          (user->opcode() != spv::Op::OpPhi || bb != GetParent(user)) &&
          "The root basic block must be the incoming edge if |user| is a phi "
          "instruction");
      assert((user->opcode() == spv::Op::OpPhi || bb == GetParent(user)) &&
             "The root basic block must be the instruction parent if |user| is "
             "not "
             "phi instruction");

      Instruction* new_def = GetOrBuildIncoming(bb->id());
      if (!new_def) {
        return false;
      }

      user->SetOperand(operand_index, {new_def->result_id()});
      rewritten_.insert(user);
      return true;
    }

    // In-place update of some managers (avoid full invalidation).
    inline void UpdateManagers() {