C++ Vunit::makeScratchBlock方法代码示例

void lower_vcall(Vunit& unit, Inst& inst, Vlabel b, size_t i) {
  auto& blocks = unit.blocks;
  auto const& vinstr = blocks[b].code[i];

  auto const is_vcall = vinstr.op == Vinstr::vcall;
  auto const vcall = vinstr.vcall_;
  auto const vinvoke = vinstr.vinvoke_;

  // We lower vinvoke in two phases, and `inst' is overwritten after the first
  // phase.  We need to save any of its parameters that we care about in the
  // second phase ahead of time.
  auto const& vargs = unit.vcallArgs[inst.args];
  auto const dests = unit.tuples[inst.d];
  auto const destType = inst.destType;

  auto const scratch = unit.makeScratchBlock();
  SCOPE_EXIT { unit.freeScratchBlock(scratch); };
  Vout v(unit, scratch, vinstr.origin);

  int32_t const adjust = (vargs.stkArgs.size() & 0x1) ? sizeof(uintptr_t) : 0;
  if (adjust) v << lea{rsp()[-adjust], rsp()};

  // Push stack arguments, in reverse order.
  for (int i = vargs.stkArgs.size() - 1; i >= 0; --i) {
    v << push{vargs.stkArgs[i]};
  }

  // Get the arguments in the proper registers.
  RegSet argRegs;
  bool needsCopy = false;
  auto doArgs = [&] (const VregList& srcs, PhysReg (*r)(size_t)) {
    VregList argDests;
    for (size_t i = 0, n = srcs.size(); i < n; ++i) {
      auto const reg = r(i);
      argDests.push_back(reg);
      argRegs |= reg;
    }
    if (argDests.size()) {
      v << copyargs{v.makeTuple(srcs),
                    v.makeTuple(std::move(argDests))};
    }
  };
  switch (arch()) {
    case Arch::X64:
    case Arch::PPC64:
      doArgs(vargs.args, rarg);
      break;
    case Arch::ARM:
      if (vargs.indirect) {
        if (vargs.args.size() > 0) {
          // First arg is a pointer to storage for the return value.
          v << copy{vargs.args[0], rret_indirect()};
          VregList rem(vargs.args.begin() + 1, vargs.args.end());
          doArgs(rem, rarg);
          needsCopy = true;
        }
      } else {
        doArgs(vargs.args, rarg);
      }
  }
  doArgs(vargs.simdArgs, rarg_simd);

  // Emit the appropriate call instruction sequence.
  emitCall(v, inst.call, argRegs);

  // Handle fixup and unwind information.
  if (inst.fixup.isValid()) {
    v << syncpoint{inst.fixup};
  }

  if (!is_vcall) {
    auto& targets = vinvoke.targets;
    v << unwind{{targets[0], targets[1]}};

    // Insert an lea fixup for any stack args at the beginning of the catch
    // block.
    if (auto rspOffset = ((vargs.stkArgs.size() + 1) & ~1) *
                         sizeof(uintptr_t)) {
      auto& taken = unit.blocks[targets[1]].code;
      assertx(taken.front().op == Vinstr::landingpad ||
              taken.front().op == Vinstr::jmp);

      Vinstr vi { lea{rsp()[rspOffset], rsp()} };
      vi.origin = taken.front().origin;

      if (taken.front().op == Vinstr::jmp) {
        taken.insert(taken.begin(), vi);
      } else {
        taken.insert(taken.begin() + 1, vi);
      }
    }

    // Write out the code so far to the end of b.  Remaining code will be
    // emitted to the next block.
    vector_splice(blocks[b].code, i, 1, blocks[scratch].code);
  } else if (vcall.nothrow) {
    v << nothrow{};
  }

  // Copy back the indirect result pointer into the return register.
//.........这里部分代码省略.........

void lower_vcall(Vunit& unit, Inst& inst, Vlabel b, size_t i) {
  auto& blocks = unit.blocks;
  auto const& vinstr = blocks[b].code[i];

  auto const is_vcall = vinstr.op == Vinstr::vcall;
  auto const vcall = vinstr.vcall_;
  auto const vinvoke = vinstr.vinvoke_;

  // We lower vinvoke in two phases, and `inst' is overwritten after the first
  // phase.  We need to save any of its parameters that we care about in the
  // second phase ahead of time.
  auto const& vargs = unit.vcallArgs[inst.args];
  auto const dests = unit.tuples[inst.d];
  auto const destType = inst.destType;

  auto const scratch = unit.makeScratchBlock();
  SCOPE_EXIT { unit.freeScratchBlock(scratch); };
  Vout v(unit, scratch, vinstr.irctx());

  // Push stack arguments, in reverse order. Push in pairs without padding
  // except for the last argument (pushed first) which should be padded if
  // there are an odd number of arguments.
  auto numArgs = vargs.stkArgs.size();
  int32_t const adjust = (numArgs & 0x1) ? sizeof(uintptr_t) : 0;
  if (adjust) {
    // Using InvalidReg below fails SSA checks and simplify pass, so just
    // push the arg twice. It's on the same cacheline and will actually
    // perform faster than an explicit lea.
    v << pushp{vargs.stkArgs[numArgs - 1], vargs.stkArgs[numArgs - 1]};
    --numArgs;
  }
  for (auto i2 = numArgs; i2 >= 2; i2 -= 2) {
    v << pushp{vargs.stkArgs[i2 - 1], vargs.stkArgs[i2 - 2]};
  }

  // Get the arguments in the proper registers.
  RegSet argRegs;
  auto doArgs = [&] (const VregList& srcs, PhysReg (*r)(size_t)) {
    VregList argDests;
    for (size_t i2 = 0, n = srcs.size(); i2 < n; ++i2) {
      auto const reg = r(i2);
      argDests.push_back(reg);
      argRegs |= reg;
    }
    if (argDests.size()) {
      v << copyargs{v.makeTuple(srcs),
                    v.makeTuple(std::move(argDests))};
    }
  };
  doArgs(vargs.indRetArgs, rarg_ind_ret);
  doArgs(vargs.args, rarg);
  doArgs(vargs.simdArgs, rarg_simd);

  // Emit the appropriate call instruction sequence.
  emitCall(v, inst.call, argRegs);

  // Handle fixup and unwind information.
  if (inst.fixup.isValid()) {
    v << syncpoint{inst.fixup};
  }

  if (!is_vcall) {
    auto& targets = vinvoke.targets;
    v << unwind{{targets[0], targets[1]}};

    // Insert an lea fixup for any stack args at the beginning of the catch
    // block.
    if (auto rspOffset = ((vargs.stkArgs.size() + 1) & ~1) *
                         sizeof(uintptr_t)) {
      auto& taken = unit.blocks[targets[1]].code;
      assertx(taken.front().op == Vinstr::landingpad ||
              taken.front().op == Vinstr::jmp);

      Vinstr vi { lea{rsp()[rspOffset], rsp()}, taken.front().irctx() };

      if (taken.front().op == Vinstr::jmp) {
        taken.insert(taken.begin(), vi);
      } else {
        taken.insert(taken.begin() + 1, vi);
      }
    }

    // Write out the code so far to the end of b.  Remaining code will be
    // emitted to the next block.
    vector_splice(blocks[b].code, i, 1, blocks[scratch].code);
  } else if (vcall.nothrow) {
    v << nothrow{};
  }
  // For vinvoke, `inst' is no longer valid after this point.

  // Copy the call result to the destination register(s).
  switch (destType) {
    case DestType::TV:
      static_assert(offsetof(TypedValue, m_data) == 0, "");
      static_assert(offsetof(TypedValue, m_type) == 8, "");

      if (dests.size() == 2) {
        switch (arch()) {
          case Arch::X64: // fall through
          case Arch::PPC64:
//.........这里部分代码省略.........