JVM 源码阅读指北

// jni.h
#ifdef __cplusplus
typedef JNIEnv_ JNIEnv;
#else
typedef const struct JNINativeInterface_ *JNIEnv;
#endif
// thread.hpp
JNIEnv        _jni_environment;
JNIEnv* jni_environment()                      { return &_jni_environment; }

// jni.h
/*
 * We use inlined functions for C++ so that programmers can write:
 *
 *    env->FindClass("java/lang/String")
 *
 * in C++ rather than:
 *
 *    (*env)->FindClass(env, "java/lang/String")
 *
 * in C.
 */
struct JNIEnv_ {
    const struct JNINativeInterface_ *functions;
#ifdef __cplusplus

    // ...
    void CallStaticVoidMethod(jclass cls, jmethodID methodID, ...) {
        va_list args;
        va_start(args,methodID);
        functions->CallStaticVoidMethodV(this,cls,methodID,args);
        va_end(args);
    }
    // ...
#endif /* __cplusplus */
}

// jni.h
struct JNINativeInterface_ {
    //...
    void (JNICALL *CallStaticVoidMethod)
      (JNIEnv *env, jclass cls, jmethodID methodID, ...);
    //...
}

// jni.cpp
JNI_ENTRY(void, jni_CallStaticVoidMethodV(JNIEnv *env, jclass cls, jmethodID methodID, va_list args))
  JNIWrapper("CallStaticVoidMethodV");
  HOTSPOT_JNI_CALLSTATICVOIDMETHODV_ENTRY(env, cls, (uintptr_t) methodID);
  DT_VOID_RETURN_MARK(CallStaticVoidMethodV);

  JavaValue jvalue(T_VOID);
  JNI_ArgumentPusherVaArg ap(methodID, args);
  jni_invoke_static(env, &jvalue, NULL, JNI_STATIC, methodID, &ap, CHECK);
JNI_END

// javaCalls.cpp
void JavaCalls::call(JavaValue* result, const methodHandle& method, JavaCallArguments* args, TRAPS) {
  // Check if we need to wrap a potential OS exception handler around thread
  // This is used for e.g. Win32 structured exception handlers
  assert(THREAD->is_Java_thread(), "only JavaThreads can make JavaCalls");
  // Need to wrap each and every time, since there might be native code down the
  // stack that has installed its own exception handlers
  os::os_exception_wrapper(call_helper, result, method, args, THREAD);
}

// javaCalls.cpp
// do call
{ JavaCallWrapper link(method, receiver, result, CHECK);
  { HandleMark hm(thread);  // HandleMark used by HandleMarkCleaner

    StubRoutines::call_stub()(
      (address)&link,
      // (intptr_t*)&(result->_value), // see NOTE above (compiler problem)
      result_val_address,          // see NOTE above (compiler problem)
      result_type,
      method(),
      entry_point,
      args->parameters(),
      args->size_of_parameters(),
      CHECK
    );

    result = link.result();  // circumvent MS C++ 5.0 compiler bug (result is clobbered across call)
    // Preserve oop return value across possible gc points
    if (oop_result_flag) {
      thread->set_vm_result((oop) result->get_jobject());
    }
  }
} // Exit JavaCallWrapper (can block - potential return oop must be preserved)

// stubGenerator_x86_64.cpp
address start = __ pc();
// ...
// C++ 里栈上分配对象
const Address entry_point   (rbp, entry_point_off    * wordSize);
// ...
// call Java function
__ BIND(parameters_done);
__ movptr(rbx, method);             // get Method*
__ movptr(c_rarg1, entry_point);    // get entry_point
__ mov(r13, rsp);                   // set sender sp
BLOCK_COMMENT("call Java function");
__ call(c_rarg1);
// ...
return start;

// method.hpp
void set_interpreter_entry(address entry) {
  assert(!is_shared(), "shared method's interpreter entry should not be changed at run time");
  if (_i2i_entry != entry) {
    _i2i_entry = entry;
  }
  if (_from_interpreted_entry != entry) {
    _from_interpreted_entry = entry;
  }
}

// method.cpp

// Called when the method_holder is getting linked. Setup entrypoints so the method
// is ready to be called from interpreter, compiler, and vtables.
void Method::link_method(const methodHandle& h_method, TRAPS) {
  // ...
  if (!is_shared()) {
    assert(adapter() == NULL, "init'd to NULL");
    address entry = Interpreter::entry_for_method(h_method);
    assert(entry != NULL, "interpreter entry must be non-null");
    // Sets both _i2i_entry and _from_interpreted_entry
    set_interpreter_entry(entry);
  }
  // ...
}

// abstractInterpreter.hpp
static address    entry_for_kind(MethodKind k)                { assert(0 <= k && k < number_of_method_entries, "illegal kind"); return _entry_table[k]; }
static address    entry_for_method(const methodHandle& m)     { return entry_for_kind(method_kind(m)); }

// templateInterpreterGenerator.cpp
#define method_entry(kind)                                              \
  { CodeletMark cm(_masm, "method entry point (kind = " #kind ")"); \
    Interpreter::_entry_table[Interpreter::kind] = generate_method_entry(Interpreter::kind); \
    Interpreter::update_cds_entry_table(Interpreter::kind); \
  }

// templateInterpreterGenerator_x86.cpp
address TemplateInterpreterGenerator::generate_normal_entry(bool synchronized) {
    // ...
    __ dispatch_next(vtos);
    // ...
}

// interp_masm_x86.cpp
void InterpreterMacroAssembler::dispatch_next(TosState state, int step, bool generate_poll) {
  // load next bytecode (load before advancing _bcp_register to prevent AGI)
  load_unsigned_byte(rbx, Address(_bcp_register, step));
  // advance _bcp_register
  increment(_bcp_register, step);
  dispatch_base(state, Interpreter::dispatch_table(state), true, generate_poll);
}

// templateInterpreter.hpp
static address*   dispatch_table(TosState state)              { return _active_table.table_for(state); }

// templateInterpreter.cpp
void TemplateInterpreter::initialize() {
  // ...
  // initialize dispatch table
  _active_table = _normal_table;
}

// templateInterpreterGenerator.cpp
void TemplateInterpreterGenerator::set_entry_points(Bytecodes::Code code) {
  // ...
  // code for short & wide version of bytecode
  if (Bytecodes::is_defined(code)) {
    Template* t = TemplateTable::template_for(code);
    assert(t->is_valid(), "just checking");
    set_short_entry_points(t, bep, cep, sep, aep, iep, lep, fep, dep, vep);
  }
  if (Bytecodes::wide_is_defined(code)) {
    Template* t = TemplateTable::template_for_wide(code);
    assert(t->is_valid(), "just checking");
    set_wide_entry_point(t, wep);
  }
  // set entry points
  EntryPoint entry(bep, zep, cep, sep, aep, iep, lep, fep, dep, vep);
  Interpreter::_normal_table.set_entry(code, entry);
  Interpreter::_wentry_point[code] = wep;
}

// templateTable.hpp
// Templates
static Template        _template_table     [Bytecodes::number_of_codes];
static Template* template_for     (Bytecodes::Code code)  { Bytecodes::check     (code); return &_template_table     [code]; }
static Template* template_for_wide(Bytecodes::Code code)  { Bytecodes::wide_check(code); return &_template_table_wide[code]; }

// templateTable.cpp
void TemplateTable::initialize() {
  if (_is_initialized) return;
  // ...
  // Java spec bytecodes                ubcp|disp|clvm|iswd  in    out   generator             argument
  def(Bytecodes::_invokevirtual       , ubcp|disp|clvm|____, vtos, vtos, invokevirtual       , f2_byte      );
  def(Bytecodes::_invokespecial       , ubcp|disp|clvm|____, vtos, vtos, invokespecial       , f1_byte      );
  def(Bytecodes::_invokestatic        , ubcp|disp|clvm|____, vtos, vtos, invokestatic        , f1_byte      );
  def(Bytecodes::_invokeinterface     , ubcp|disp|clvm|____, vtos, vtos, invokeinterface     , f1_byte      );
  def(Bytecodes::_invokedynamic       , ubcp|disp|clvm|____, vtos, vtos, invokedynamic       , f1_byte      );
  def(Bytecodes::_new                 , ubcp|____|clvm|____, vtos, atos, _new                ,  _           );
  // ...
}

// templateTable_x86.cpp
void TemplateTable::_new() {
  //...
  Register rarg1 = LP64_ONLY(c_rarg1) NOT_LP64(rax);
  Register rarg2 = LP64_ONLY(c_rarg2) NOT_LP64(rdx);

  __ get_constant_pool(rarg1);
  __ get_unsigned_2_byte_index_at_bcp(rarg2, 1);
  call_VM(rax, CAST_FROM_FN_PTR(address, InterpreterRuntime::_new), rarg1, rarg2);
   __ verify_oop(rax);

  // continue
  __ bind(done);
}

// interpreterRuntime.cpp
IRT_ENTRY(void, InterpreterRuntime::_new(JavaThread* thread, ConstantPool* pool, int index))
  //...
  oop obj = klass->allocate_instance(CHECK);
  thread->set_vm_result(obj);
IRT_END

// instanceKlass.cpp
instanceOop InstanceKlass::allocate_instance(TRAPS) {
  //...
  i = (instanceOop)Universe::heap()->obj_allocate(this, size, CHECK_NULL);
  if (has_finalizer_flag && !RegisterFinalizersAtInit) {
    i = register_finalizer(i, CHECK_NULL);
  }
  return i;
}

// collectedHeap.cpp
oop CollectedHeap::obj_allocate(Klass* klass, int size, TRAPS) {
  ObjAllocator allocator(klass, size, THREAD);
  return allocator.allocate();
}

// memAllocator.cpp
oop MemAllocator::allocate() const {
  oop obj = NULL;
  {
    Allocation allocation(*this, &obj);
    HeapWord* mem = mem_allocate(allocation);
    if (mem != NULL) {
      obj = initialize(mem);
    }
  }
  return obj;
}

HeapWord* MemAllocator::mem_allocate(Allocation& allocation) const {
  if (UseTLAB) {
    HeapWord* result = allocate_inside_tlab(allocation);
    if (result != NULL) {
      return result;
    }
  }

  return allocate_outside_tlab(allocation);
}

HeapWord* MemAllocator::allocate_outside_tlab(Allocation& allocation) const {
  allocation._allocated_outside_tlab = true;
  HeapWord* mem = _heap->mem_allocate(_word_size, &allocation._overhead_limit_exceeded);
  if (mem == NULL) {
    return mem;
  }

  NOT_PRODUCT(_heap->check_for_non_bad_heap_word_value(mem, _word_size));
  size_t size_in_bytes = _word_size * HeapWordSize;
  _thread->incr_allocated_bytes(size_in_bytes);

  return mem;
}

// g1CollectedHeap.cpp
HeapWord*
G1CollectedHeap::mem_allocate(size_t word_size,
                              bool*  gc_overhead_limit_was_exceeded) {
  assert_heap_not_locked_and_not_at_safepoint();

  if (is_humongous(word_size)) {
    return attempt_allocation_humongous(word_size);
  }
  size_t dummy = 0;
  return attempt_allocation(word_size, word_size, &dummy);
}

inline HeapWord* G1CollectedHeap::attempt_allocation(size_t min_word_size,
                                                     size_t desired_word_size,
                                                     size_t* actual_word_size) {
  //...
  HeapWord* result = _allocator->attempt_allocation(min_word_size, desired_word_size, actual_word_size);

  if (result == NULL) {
    *actual_word_size = desired_word_size;
    result = attempt_allocation_slow(desired_word_size);
  }
  //...
}

// g1CollectedHeap.cpp
HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) {
    //...
    if (should_try_gc) {
      bool succeeded;
      result = do_collection_pause(word_size, gc_count_before, &succeeded,
                                   GCCause::_g1_inc_collection_pause);
      //...
    }
    //...
}

HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
                                               uint gc_count_before,
                                               bool* succeeded,
                                               GCCause::Cause gc_cause) {
  assert_heap_not_locked_and_not_at_safepoint();
  VM_G1CollectForAllocation op(word_size,
                               gc_count_before,
                               gc_cause,
                               false, /* should_initiate_conc_mark */
                               g1_policy()->max_pause_time_ms());
  VMThread::execute(&op);

  HeapWord* result = op.result();
  bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
  assert(result == NULL || ret_succeeded,
         "the result should be NULL if the VM did not succeed");
  *succeeded = ret_succeeded;

  assert_heap_not_locked();
  return result;
}

// templateTable_x86.cpp
void TemplateTable::invokevirtual(int byte_no) {
  transition(vtos, vtos);
  assert(byte_no == f2_byte, "use this argument");
  prepare_invoke(byte_no,
                 rbx,    // method or vtable index
                 noreg,  // unused itable index
                 rcx, rdx); // recv, flags

  // rbx: index
  // rcx: receiver
  // rdx: flags

  invokevirtual_helper(rbx, rcx, rdx);
}
void TemplateTable::invokevirtual_helper(Register index,
                                         Register recv,
                                         Register flags) {
  //...
  __ jump_from_interpreted(method, rdx);
}

// interp_masm_x86.cpp
void InterpreterMacroAssembler::jump_from_interpreted(Register method, Register temp) {
  //...
  jmp(Address(method, Method::from_interpreted_offset()));
}

// method.hpp
static ByteSize from_interpreted_offset()      { return byte_offset_of(Method, _from_interpreted_entry ); }

// templateInterpreterGenerator_x86.cpp
address TemplateInterpreterGenerator::generate_normal_entry(bool synchronized) {
  //...
  // increment invocation count & check for overflow
  Label invocation_counter_overflow;
  Label profile_method;
  Label profile_method_continue;
  if (inc_counter) {
    generate_counter_incr(&invocation_counter_overflow,
                          &profile_method,
                          &profile_method_continue);
    if (ProfileInterpreter) {
      __ bind(profile_method_continue);
    }
  }
  //...
  // invocation counter overflow
  if (inc_counter) {
    if (ProfileInterpreter) {
      // We have decided to profile this method in the interpreter
      __ bind(profile_method);
      __ call_VM(noreg, CAST_FROM_FN_PTR(address, InterpreterRuntime::profile_method));
      __ set_method_data_pointer_for_bcp();
      __ get_method(rbx);
      __ jmp(profile_method_continue);
    }
    // Handle overflow of counter and compile method
    __ bind(invocation_counter_overflow);
    generate_counter_overflow(continue_after_compile);
  }
  return entry_point;
}

void TemplateInterpreterGenerator::generate_counter_overflow(Label& do_continue) {
  //...
  __ call_VM(noreg,
             CAST_FROM_FN_PTR(address,
                              InterpreterRuntime::frequency_counter_overflow),
             rarg);
  //...
}

//interpreterRuntime.cpp
nmethod* InterpreterRuntime::frequency_counter_overflow(JavaThread* thread, address branch_bcp) {
  nmethod* nm = frequency_counter_overflow_inner(thread, branch_bcp);
  //...
}

IRT_ENTRY(nmethod*,
          InterpreterRuntime::frequency_counter_overflow_inner(JavaThread* thread, address branch_bcp))
  //...
  nmethod* osr_nm = CompilationPolicy::policy()->event(method, method, branch_bci, bci, CompLevel_none, NULL, thread);
  //...
IRT_END

//simpleThresholdPolicy.cpp
nmethod* SimpleThresholdPolicy::event(const methodHandle& method, const methodHandle& inlinee,
                                      int branch_bci, int bci, CompLevel comp_level, CompiledMethod* nm, JavaThread* thread) {
  //...
  if (bci == InvocationEntryBci) {
    method_invocation_event(method, inlinee, comp_level, nm, thread);
  } else {
    // method == inlinee if the event originated in the main method
    method_back_branch_event(method, inlinee, bci, comp_level, nm, thread);
    // Check if event led to a higher level OSR compilation
    nmethod* osr_nm = inlinee->lookup_osr_nmethod_for(bci, comp_level, false);
    if (osr_nm != NULL && osr_nm->comp_level() > comp_level) {
      // Perform OSR with new nmethod
      return osr_nm;
    }
  }
  return NULL;
}

void SimpleThresholdPolicy::method_invocation_event(const methodHandle& mh, const methodHandle& imh,
                                                      CompLevel level, CompiledMethod* nm, JavaThread* thread) {
  if (should_create_mdo(mh(), level)) {
    create_mdo(mh, thread);
  }
  CompLevel next_level = call_event(mh(), level, thread);
  if (next_level != level) {
    if (maybe_switch_to_aot(mh, level, next_level, thread)) {
      // No JITting necessary
      return;
    }
    if (is_compilation_enabled() && !CompileBroker::compilation_is_in_queue(mh)) {
      compile(mh, InvocationEntryBci, next_level, thread);
    }
  }
}

void SimpleThresholdPolicy::compile(const methodHandle& mh, int bci, CompLevel level, JavaThread* thread) {
  //...
  if (!CompileBroker::compilation_is_in_queue(mh)) {
    if (PrintTieredEvents) {
      print_event(COMPILE, mh, mh, bci, level);
    }
    submit_compile(mh, bci, level, thread);
  }
}

void SimpleThresholdPolicy::submit_compile(const methodHandle& mh, int bci, CompLevel level, JavaThread* thread) {
  int hot_count = (bci == InvocationEntryBci) ? mh->invocation_count() : mh->backedge_count();
  update_rate(os::javaTimeMillis(), mh());
  CompileBroker::compile_method(mh, bci, level, mh, hot_count, CompileTask::Reason_Tiered, thread);
}

nmethod* CompileBroker::compile_method(const methodHandle& method, int osr_bci,
                                         int comp_level,
                                         const methodHandle& hot_method, int hot_count,
                                         CompileTask::CompileReason compile_reason,
                                         DirectiveSet* directive,
                                         Thread* THREAD) {
        //...
        compile_method_base(method, osr_bci, comp_level, hot_method, hot_count, compile_reason, is_blocking, THREAD);
        //...
}

void CompileBroker::compile_method_base(const methodHandle& method,
                                        int osr_bci,
                                        int comp_level,
                                        const methodHandle& hot_method,
                                        int hot_count,
                                        CompileTask::CompileReason compile_reason,
                                        bool blocking,
                                        Thread* thread) {
        //...
        task = create_compile_task(queue,
                               compile_id, method,
                               osr_bci, comp_level,
                               hot_method, hot_count, compile_reason,
                               blocking);
        //...
}

CompileTask* CompileBroker::create_compile_task(CompileQueue*       queue,
                                                int                 compile_id,
                                                const methodHandle& method,
                                                int                 osr_bci,
                                                int                 comp_level,
                                                const methodHandle& hot_method,
                                                int                 hot_count,
                                                CompileTask::CompileReason compile_reason,
                                                bool                blocking) {
  CompileTask* new_task = CompileTask::allocate();
  new_task->initialize(compile_id, method, osr_bci, comp_level,
                       hot_method, hot_count, compile_reason,
                       blocking);
  queue->add(new_task);
  return new_task;
}

// thread.cpp
static void compiler_thread_entry(JavaThread* thread, TRAPS) {
  assert(thread->is_Compiler_thread(), "must be compiler thread");
  CompileBroker::compiler_thread_loop();
}

// compileBroker.cpp
void CompileBroker::compiler_thread_loop() {
    //...
    // Compile the method.
    if ((UseCompiler || AlwaysCompileLoopMethods) && CompileBroker::should_compile_new_jobs()) {
        invoke_compiler_on_method(task);
        thread->start_idle_timer();
    } else {
        // After compilation is disabled, remove remaining methods from queue
        method->clear_queued_for_compilation();
        task->set_failure_reason("compilation is disabled");
    }
    //...
}

void CompileBroker::invoke_compiler_on_method(CompileTask* task) {
    //...
    comp->compile_method(&ci_env, target, osr_bci, directive);
    //...
}

//c1_Compiler.cpp
void Compiler::compile_method(ciEnv* env, ciMethod* method, int entry_bci, DirectiveSet* directive) {
    BufferBlob* buffer_blob = CompilerThread::current()->get_buffer_blob();
    assert(buffer_blob != NULL, "Must exist");
    // invoke compilation
    {
        // We are nested here because we need for the destructor
        // of Compilation to occur before we release the any
        // competing compiler thread
        ResourceMark rm;
        Compilation c(this, env, method, entry_bci, buffer_blob, directive);
    }
}

//c1_Compilation.cpp
Compilation::Compilation(AbstractCompiler* compiler, ciEnv* env, ciMethod* method,
int osr_bci, BufferBlob* buffer_blob, DirectiveSet* directive)
//...
{
    //...
    compile_method();
    //...
}

void Compilation::compile_method() {
    //...
    if (InstallMethods) {
        // install code
        PhaseTraceTime timeit(_t_codeinstall);
        install_code(frame_size);
    }
    //...
}

void Compilation::install_code(int frame_size) {
    // frame_size is in 32-bit words so adjust it intptr_t words
    assert(frame_size == frame_map()->framesize(), "must match");
    assert(in_bytes(frame_map()->framesize_in_bytes()) % sizeof(intptr_t) == 0, "must be at least pointer aligned");
    _env->register_method(
        method(),
        osr_bci(),
        &_offsets,
        in_bytes(_frame_map->sp_offset_for_orig_pc()),
        code(),
        in_bytes(frame_map()->framesize_in_bytes()) / sizeof(intptr_t),
        debug_info_recorder()->_oopmaps,
        exception_handler_table(),
        implicit_exception_table(),
        compiler(),
        has_unsafe_access(),
        SharedRuntime::is_wide_vector(max_vector_size())
        );
}

// ciEnv.cpp
void ciEnv::register_method(ciMethod* target,
                            int entry_bci,
                            CodeOffsets* offsets,
                            int orig_pc_offset,
                            CodeBuffer* code_buffer,
                            int frame_words,
                            OopMapSet* oop_map_set,
                            ExceptionHandlerTable* handler_table,
                            ImplicitExceptionTable* inc_table,
                            AbstractCompiler* compiler,
                            bool has_unsafe_access,
                            bool has_wide_vectors,
                            RTMState  rtm_state) {
  //...
  // Allow the code to be executed
  method->set_code(method, nm);
  //...
}


// method.cpp
// Install compiled code.  Instantly it can execute.
void Method::set_code(const methodHandle& mh, CompiledMethod *code) {
  //...
  // Instantly compiled code can execute.
  if (!mh->is_method_handle_intrinsic())
    mh->_from_interpreted_entry = mh->get_i2c_entry();
}