JDK14/Java14源码在线阅读

/*
 * Copyright (c) 2003, 2018, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#include "precompiled.hpp"
#include "asm/macroAssembler.hpp"
#include "code/vtableStubs.hpp"
#include "interp_masm_x86.hpp"
#include "memory/resourceArea.hpp"
#include "oops/compiledICHolder.hpp"
#include "oops/instanceKlass.hpp"
#include "oops/klassVtable.hpp"
#include "runtime/sharedRuntime.hpp"
#include "vmreg_x86.inline.hpp"
#ifdef COMPILER2
#include "opto/runtime.hpp"
#endif

// machine-dependent part of VtableStubs: create VtableStub of correct size and
// initialize its code

#define __ masm->

#ifndef PRODUCT
extern "C" void bad_compiled_vtable_index(JavaThread* thread, oop receiver, int index);
#endif

VtableStub* VtableStubs::create_vtable_stub(int vtable_index) {
  // Read "A word on VtableStub sizing" in share/code/vtableStubs.hpp for details on stub sizing.
  const int stub_code_length = code_size_limit(true);
  VtableStub* s = new(stub_code_length) VtableStub(true, vtable_index);
  // Can be NULL if there is no free space in the code cache.
  if (s == NULL) {
    return NULL;
  }

  // Count unused bytes in instruction sequences of variable size.
  // We add them to the computed buffer size in order to avoid
  // overflow in subsequently generated stubs.
  address   start_pc;
  int       slop_bytes = 0;
  int       slop_delta = 0;
  // No variance was detected in vtable stub sizes. Setting index_dependent_slop == 0 will unveil any deviation from this observation.
  const int index_dependent_slop     = 0;

  ResourceMark    rm;
  CodeBuffer      cb(s->entry_point(), stub_code_length);
  MacroAssembler* masm = new MacroAssembler(&cb);

#if (!defined(PRODUCT) && defined(COMPILER2))
  if (CountCompiledCalls) {
    __ incrementl(ExternalAddress((address) SharedRuntime::nof_megamorphic_calls_addr()));
  }
#endif

  // get receiver (need to skip return address on top of stack)
  assert(VtableStub::receiver_location() == j_rarg0->as_VMReg(), "receiver expected in j_rarg0");

  // Free registers (non-args) are rax, rbx

  // get receiver klass
  address npe_addr = __ pc();
  __ load_klass(rax, j_rarg0);

#ifndef PRODUCT
  if (DebugVtables) {
    Label L;
    start_pc = __ pc();
    // check offset vs vtable length
    __ cmpl(Address(rax, Klass::vtable_length_offset()), vtable_index*vtableEntry::size());
    slop_delta  = 12 - (__ pc() - start_pc);  // cmpl varies in length, depending on data
    slop_bytes += slop_delta;
    assert(slop_delta >= 0, "negative slop(%d) encountered, adjust code size estimate!", slop_delta);

    __ jcc(Assembler::greater, L);
    __ movl(rbx, vtable_index);
    // VTABLE TODO: find upper bound for call_VM length.
    start_pc = __ pc();
    __ call_VM(noreg, CAST_FROM_FN_PTR(address, bad_compiled_vtable_index), j_rarg0, rbx);
    slop_delta  = 480 - (__ pc() - start_pc);
    slop_bytes += slop_delta;
    assert(slop_delta >= 0, "negative slop(%d) encountered, adjust code size estimate!", slop_delta);
    __ bind(L);
  }
#endif // PRODUCT

  const Register method = rbx;

  // load Method* and target address
  start_pc = __ pc();
  __ lookup_virtual_method(rax, vtable_index, method);
  slop_delta  = 8 - (int)(__ pc() - start_pc);
  slop_bytes += slop_delta;
  assert(slop_delta >= 0, "negative slop(%d) encountered, adjust code size estimate!", slop_delta);

#ifndef PRODUCT
  if (DebugVtables) {
    Label L;
    __ cmpptr(method, (int32_t)NULL_WORD);
    __ jcc(Assembler::equal, L);
    __ cmpptr(Address(method, Method::from_compiled_offset()), (int32_t)NULL_WORD);
    __ jcc(Assembler::notZero, L);
    __ stop("Vtable entry is NULL");
    __ bind(L);
  }
#endif // PRODUCT

  // rax: receiver klass
  // method (rbx): Method*
  // rcx: receiver
  address ame_addr = __ pc();
  __ jmp( Address(rbx, Method::from_compiled_offset()));

  masm->flush();
  slop_bytes += index_dependent_slop; // add'l slop for size variance due to large itable offsets
  bookkeeping(masm, tty, s, npe_addr, ame_addr, true, vtable_index, slop_bytes, index_dependent_slop);

  return s;
}


VtableStub* VtableStubs::create_itable_stub(int itable_index) {
  // Read "A word on VtableStub sizing" in share/code/vtableStubs.hpp for details on stub sizing.
  const int stub_code_length = code_size_limit(false);
  VtableStub* s = new(stub_code_length) VtableStub(false, itable_index);
  // Can be NULL if there is no free space in the code cache.
  if (s == NULL) {
    return NULL;
  }
  // Count unused bytes in instruction sequences of variable size.
  // We add them to the computed buffer size in order to avoid
  // overflow in subsequently generated stubs.
  address   start_pc;
  int       slop_bytes = 0;
  int       slop_delta = 0;
  const int index_dependent_slop = (itable_index == 0) ? 4 :     // code size change with transition from 8-bit to 32-bit constant (@index == 16).
                                   (itable_index < 16) ? 3 : 0;  // index == 0 generates even shorter code.

  ResourceMark    rm;
  CodeBuffer      cb(s->entry_point(), stub_code_length);
  MacroAssembler *masm = new MacroAssembler(&cb);

#if (!defined(PRODUCT) && defined(COMPILER2))
  if (CountCompiledCalls) {
    __ incrementl(ExternalAddress((address) SharedRuntime::nof_megamorphic_calls_addr()));
  }
#endif // PRODUCT

  // Entry arguments:
  //  rax: CompiledICHolder
  //  j_rarg0: Receiver

  // Most registers are in use; we'll use rax, rbx, r10, r11
  // (various calling sequences use r[cd]x, r[sd]i, r[89]; stay away from them)
  const Register recv_klass_reg     = r10;
  const Register holder_klass_reg   = rax; // declaring interface klass (DECC)
  const Register resolved_klass_reg = rbx; // resolved interface klass (REFC)
  const Register temp_reg           = r11;

  const Register icholder_reg = rax;
  __ movptr(resolved_klass_reg, Address(icholder_reg, CompiledICHolder::holder_klass_offset()));
  __ movptr(holder_klass_reg,   Address(icholder_reg, CompiledICHolder::holder_metadata_offset()));

  Label L_no_such_interface;

  // get receiver klass (also an implicit null-check)
  assert(VtableStub::receiver_location() == j_rarg0->as_VMReg(), "receiver expected in j_rarg0");
  address npe_addr = __ pc();
  __ load_klass(recv_klass_reg, j_rarg0);

  start_pc = __ pc();

  // Receiver subtype check against REFC.
  // Destroys recv_klass_reg value.
  __ lookup_interface_method(// inputs: rec. class, interface
                             recv_klass_reg, resolved_klass_reg, noreg,
                             // outputs:  scan temp. reg1, scan temp. reg2
                             recv_klass_reg, temp_reg,
                             L_no_such_interface,
                             /*return_method=*/false);

  const ptrdiff_t  typecheckSize = __ pc() - start_pc;
  start_pc = __ pc();

  // Get selected method from declaring class and itable index
  const Register method = rbx;
  __ load_klass(recv_klass_reg, j_rarg0);   // restore recv_klass_reg
  __ lookup_interface_method(// inputs: rec. class, interface, itable index
                             recv_klass_reg, holder_klass_reg, itable_index,
                             // outputs: method, scan temp. reg
                             method, temp_reg,
                             L_no_such_interface);

  const ptrdiff_t  lookupSize = __ pc() - start_pc;

  // We expect we need index_dependent_slop extra bytes. Reason:
  // The emitted code in lookup_interface_method changes when itable_index exceeds 15.
  // For linux, a very narrow estimate would be 112, but Solaris requires some more space (130).
  const ptrdiff_t estimate = 136;
  const ptrdiff_t codesize = typecheckSize + lookupSize + index_dependent_slop;
  slop_delta  = (int)(estimate - codesize);
  slop_bytes += slop_delta;
  assert(slop_delta >= 0, "itable #%d: Code size estimate (%d) for lookup_interface_method too small, required: %d", itable_index, (int)estimate, (int)codesize);

  // If we take a trap while this arg is on the stack we will not
  // be able to walk the stack properly. This is not an issue except
  // when there are mistakes in this assembly code that could generate
  // a spurious fault. Ask me how I know...

  // method (rbx): Method*
  // j_rarg0: receiver

#ifdef ASSERT
  if (DebugVtables) {
    Label L2;
    __ cmpptr(method, (int32_t)NULL_WORD);
    __ jcc(Assembler::equal, L2);

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