C++ Vout类代码示例

void emitCall(Vout& v, CppCall target, RegSet args) {
  switch (target.kind()) {
    case CppCall::Kind::Direct:
      v << call{static_cast<TCA>(target.address()), args};
      return;
    case CppCall::Kind::Virtual:
      // Virtual call.  Load method's address from proper offset off of object in
      // rdi, using rax as scratch.
      v << load{*reg::rdi, reg::rax};
      v << callm{reg::rax[target.vtableOffset()], args};
      return;
    case CppCall::Kind::ArrayVirt: {
      auto const addr = reinterpret_cast<intptr_t>(target.arrayTable());
      v << loadzbl{reg::rdi[HeaderKindOffset], reg::eax};
      if (deltaFits(addr, sz::dword)) {
        v << callm{baseless(reg::rax * 8 + addr), args};
      } else {
        auto const base = v.makeReg();
        v << ldimmq{addr, base};
        v << callm{base[reg::rax * 8], args};
      }
      static_assert(sizeof(HeaderKind) == 1, "");
      return;
    }
    case CppCall::Kind::Destructor:
      // this movzbq is only needed because callers aren't required to
      // zero-extend the type.
      auto zextType = v.makeReg();
      v << movzbq{target.reg(), zextType};
      auto dtor_ptr = lookupDestructor(v, zextType);
      v << callm{dtor_ptr, args};
      return;
  }
  not_reached();
}

PhysRegSaverParity::PhysRegSaverParity(int parity, Vout& v,
                                       RegSet regs)
    : m_as(nullptr)
    , m_v(&v)
    , m_regs(regs)
{
  auto xmm = regs & x64::kXMMRegs;
  auto gpr = regs - xmm;
  m_adjust = (parity & 0x1) == (gpr.size() & 0x1) ? 8 : 0;
  if (!xmm.empty()) {
    v << subqi{16 * xmm.size(), reg::rsp, reg::rsp, v.makeReg()};
    int offset = 0;
    xmm.forEach([&](PhysReg pr) {
      v << storedqu{pr, reg::rsp[offset]};
      offset += 16;
    });
  }
  gpr.forEach([&] (PhysReg pr) {
    v << push{pr};
  });
  if (m_adjust) {
    // Maintain stack evenness for SIMD compatibility.
    v << subqi{m_adjust, reg::rsp, reg::rsp, v.makeReg()};
  }
}

void storeTV(Vout& v, Vptr dst, Vloc srcLoc, const SSATmp* src) {
  auto const type = src->type();

  if (srcLoc.isFullSIMD()) {
    // The whole TV is stored in a single SIMD reg.
    assertx(RuntimeOption::EvalHHIRAllocSIMDRegs);
    v << storeups{srcLoc.reg(), dst};
    return;
  }

  if (type.needsReg()) {
    assertx(srcLoc.hasReg(1));
    v << storeb{srcLoc.reg(1), dst + TVOFF(m_type)};
  } else {
    v << storeb{v.cns(type.toDataType()), dst + TVOFF(m_type)};
  }

  // We ignore the values of statically nullish types.
  if (src->isA(TNull) || src->isA(TNullptr)) return;

  // Store the value.
  if (src->hasConstVal()) {
    // Skip potential zero-extend if we know the value.
    v << store{v.cns(src->rawVal()), dst + TVOFF(m_data)};
  } else {
    assertx(srcLoc.hasReg(0));
    auto const extended = zeroExtendIfBool(v, src->type(), srcLoc.reg(0));
    v << store{extended, dst + TVOFF(m_data)};
  }
}

void emitRB(Vout& v, Trace::RingBufferType t, const char* msg) {
  if (!Trace::moduleEnabled(Trace::ringbuffer, 1)) {
    return;
  }
  v << vcall{CppCall::direct(Trace::ringbufferMsg),
             v.makeVcallArgs({{v.cns(msg), v.cns(strlen(msg)), v.cns(t)}}),
             v.makeTuple({})};
}

Vreg check_subcls(Vout& v, Vreg sf, Vreg d, Vreg lhs, Cls rhs, Len rhsVecLen) {
  return cond(v, CC_NB, sf, d,
       [&] (Vout& v) {
         return check_clsvec(v, v.makeReg(), lhs, rhs, rhsVecLen);
       },
       [&] (Vout& v) { return v.cns(false); }
      );
}

Vreg checkRDSHandleInitialized(Vout& v, rds::Handle ch) {
  assertx(rds::isNormalHandle(ch));
  auto const gen = v.makeReg();
  auto const sf = v.makeReg();
  v << loadb{rvmtl()[rds::genNumberHandleFrom(ch)], gen};
  v << cmpbm{gen, rvmtl()[rds::currentGenNumberHandle()], sf};
  return sf;
}

void emitAssertRefCount(Vout& v, Vreg base) {
  auto const sf = v.makeReg();
  v << cmplim{StaticValue, base[FAST_REFCOUNT_OFFSET], sf};
  ifThen(v, CC_NLE, sf, [&](Vout& v) {
    auto const sf = v.makeReg();
    v << cmplim{RefCountMaxRealistic, base[FAST_REFCOUNT_OFFSET], sf};
    ifThen(v, CC_NBE, sf, [&](Vout& v) { v << ud2{}; });
  });
}

void ifThen(Vout& v, ConditionCode cc, Vreg sf, Then thenBlock) {
  auto then = v.makeBlock();
  auto done = v.makeBlock();
  v << jcc{cc, sf, {done, then}};
  v = then;
  thenBlock(v);
  if (!v.closed()) v << jmp{done};
  v = done;
}

void ifZero(Vout& v, unsigned bit, Vreg r, Then thenBlock) {
  auto then = v.makeBlock();
  auto done = v.makeBlock();
  v << tbcc{vixl::eq, bit, r, {done, then}};
  v = then;
  thenBlock(v);
  if (!v.closed()) v << jmp{done};
  v = done;
}

Vptr lookupDestructor(Vout& v, Vreg type) {
  auto const table = reinterpret_cast<intptr_t>(g_destructors);
  always_assert_flog(deltaFits(table, sz::dword),
    "Destructor function table is expected to be in the data "
    "segment, with addresses less than 2^31"
  );
  auto index = v.makeReg();
  v << shrli{kShiftDataTypeToDestrIndex, type, index, v.makeReg()};
  return baseless(index * 8 + safe_cast<int>(table));
}

void cmpLowPtrImpl(Vout& v, Vreg sf, const void* ptr, Vptr mem, size_t size) {
  if (size == 8) {
    v << cmpqm{v.cns(ptr), mem, sf};
  } else if (size == 4) {
    auto const ptrImm = safe_cast<uint32_t>(reinterpret_cast<intptr_t>(ptr));
    v << cmplm{v.cns(ptrImm), mem, sf};
  } else {
    not_implemented();
  }
}

void emitCmpClass(Vout& v, Vreg sf, const Class* cls, Vptr mem) {
  auto size = sizeof(LowPtr<Class>);
  if (size == 8) {
    v << cmpqm{v.cns(cls), mem, sf};
  } else if (size == 4) {
    auto const clsImm = safe_cast<uint32_t>(reinterpret_cast<intptr_t>(cls));
    v << cmplm{v.cns(clsImm), mem, sf};
  } else {
    not_implemented();
  }
}

void emitIncRefWork(Vout& v, Vreg data, Vreg type) {
  auto const sf = v.makeReg();
  emitCmpTVType(v, sf, KindOfRefCountThreshold, type);
  // ifRefCountType
  ifThen(v, CC_G, sf, [&] (Vout& v) {
    auto const sf2 = v.makeReg();
    // ifNonStatic
    v << cmplim{0, data[FAST_REFCOUNT_OFFSET], sf2};
    ifThen(v, CC_GE, sf2, [&] (Vout& v) { emitIncRef(v, data); });
  });
}

void ifThenElse(Vout& v, ConditionCode cc, Vreg sf, Then thenBlock,
                Else elseBlock) {
  auto thenLabel = v.makeBlock();
  auto elseLabel = v.makeBlock();
  auto done = v.makeBlock();
  v << jcc{cc, sf, {elseLabel, thenLabel}};
  v = thenLabel;
  thenBlock(v);
  if (!v.closed()) v << jmp{done};
  v = elseLabel;
  elseBlock(v);
  if (!v.closed()) v << jmp{done};
  v = done;
}

void emitDecRefWorkObj(Vout& v, Vreg obj) {
  auto const shouldRelease = v.makeReg();
  v << cmplim{1, obj[FAST_REFCOUNT_OFFSET], shouldRelease};
  ifThenElse(
    v, CC_E, shouldRelease,
    [&] (Vout& v) {
      // Put fn inside vcall{} triggers a compiler internal error (gcc 4.4.7)
      auto const fn = CallSpec::method(&ObjectData::release);
      v << vcall{fn, v.makeVcallArgs({{obj}}), v.makeTuple({})};
    },
    [&] (Vout& v) {
      emitDecRef(v, obj);
    }
  );
}