1 /*
   2  * Copyright (c) 1997, 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "asm/macroAssembler.hpp"
  27 #include "classfile/javaClasses.inline.hpp"
  28 #include "interpreter/interpreter.hpp"
  29 #include "interpreter/interpreterRuntime.hpp"
  30 #include "memory/allocation.inline.hpp"
  31 #include "prims/methodHandles.hpp"
  32 
  33 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
  34 
  35 #define __ _masm->
  36 
  37 #ifdef PRODUCT
  38 #define BLOCK_COMMENT(str) /* nothing */
  39 #define STOP(error) stop(error)
  40 #else
  41 #define BLOCK_COMMENT(str) __ block_comment(str)
  42 #define STOP(error) block_comment(error); __ stop(error)
  43 #endif
  44 
  45 #define BIND(label) bind(label); BLOCK_COMMENT(#label ":")
  46 
  47 void MethodHandles::load_klass_from_Class(MacroAssembler* _masm, Register klass_reg) {
  48   if (VerifyMethodHandles)
  49     verify_klass(_masm, klass_reg, SystemDictionary::WK_KLASS_ENUM_NAME(java_lang_Class),
  50                  "MH argument is a Class");
  51   __ movptr(klass_reg, Address(klass_reg, java_lang_Class::klass_offset_in_bytes()));
  52 }
  53 
  54 #ifdef ASSERT
  55 static int check_nonzero(const char* xname, int x) {
  56   assert(x != 0, err_msg("%s should be nonzero", xname));
  57   return x;
  58 }
  59 #define NONZERO(x) check_nonzero(#x, x)
  60 #else //ASSERT
  61 #define NONZERO(x) (x)
  62 #endif //ASSERT
  63 
  64 #ifdef ASSERT
  65 void MethodHandles::verify_klass(MacroAssembler* _masm,
  66                                  Register obj, SystemDictionary::WKID klass_id,
  67                                  const char* error_message) {
  68   Klass** klass_addr = SystemDictionary::well_known_klass_addr(klass_id);
  69   KlassHandle klass = SystemDictionary::well_known_klass(klass_id);
  70   Register temp = rdi;
  71   Register temp2 = noreg;
  72   LP64_ONLY(temp2 = rscratch1);  // used by MacroAssembler::cmpptr
  73   Label L_ok, L_bad;
  74   BLOCK_COMMENT("verify_klass {");
  75   __ verify_oop(obj);
  76   __ testptr(obj, obj);
  77   __ jcc(Assembler::zero, L_bad);
  78   __ push(temp); if (temp2 != noreg)  __ push(temp2);
  79 #define UNPUSH { if (temp2 != noreg)  __ pop(temp2);  __ pop(temp); }
  80   __ load_klass(temp, obj);
  81   __ cmpptr(temp, ExternalAddress((address) klass_addr));
  82   __ jcc(Assembler::equal, L_ok);
  83   intptr_t super_check_offset = klass->super_check_offset();
  84   __ movptr(temp, Address(temp, super_check_offset));
  85   __ cmpptr(temp, ExternalAddress((address) klass_addr));
  86   __ jcc(Assembler::equal, L_ok);
  87   UNPUSH;
  88   __ bind(L_bad);
  89   __ STOP(error_message);
  90   __ BIND(L_ok);
  91   UNPUSH;
  92   BLOCK_COMMENT("} verify_klass");
  93 }
  94 
  95 void MethodHandles::verify_ref_kind(MacroAssembler* _masm, int ref_kind, Register member_reg, Register temp) {
  96   Label L;
  97   BLOCK_COMMENT("verify_ref_kind {");
  98   __ movl(temp, Address(member_reg, NONZERO(java_lang_invoke_MemberName::flags_offset_in_bytes())));
  99   __ shrl(temp, java_lang_invoke_MemberName::MN_REFERENCE_KIND_SHIFT);
 100   __ andl(temp, java_lang_invoke_MemberName::MN_REFERENCE_KIND_MASK);
 101   __ cmpl(temp, ref_kind);
 102   __ jcc(Assembler::equal, L);
 103   { char* buf = NEW_C_HEAP_ARRAY(char, 100, mtInternal);
 104     jio_snprintf(buf, 100, "verify_ref_kind expected %x", ref_kind);
 105     if (ref_kind == JVM_REF_invokeVirtual ||
 106         ref_kind == JVM_REF_invokeSpecial)
 107       // could do this for all ref_kinds, but would explode assembly code size
 108       trace_method_handle(_masm, buf);
 109     __ STOP(buf);
 110   }
 111   BLOCK_COMMENT("} verify_ref_kind");
 112   __ bind(L);
 113 }
 114 
 115 #endif //ASSERT
 116 
 117 void MethodHandles::jump_from_method_handle(MacroAssembler* _masm, Register method, Register temp,
 118                                             bool for_compiler_entry) {
 119   assert(method == rbx, "interpreter calling convention");
 120 
 121    Label L_no_such_method;
 122    __ testptr(rbx, rbx);
 123    __ jcc(Assembler::zero, L_no_such_method);
 124 
 125   __ verify_method_ptr(method);
 126 
 127   if (!for_compiler_entry && JvmtiExport::can_post_interpreter_events()) {
 128     Label run_compiled_code;
 129     // JVMTI events, such as single-stepping, are implemented partly by avoiding running
 130     // compiled code in threads for which the event is enabled.  Check here for
 131     // interp_only_mode if these events CAN be enabled.
 132 #ifdef _LP64
 133     Register rthread = r15_thread;
 134 #else
 135     Register rthread = temp;
 136     __ get_thread(rthread);
 137 #endif
 138     // interp_only is an int, on little endian it is sufficient to test the byte only
 139     // Is a cmpl faster?
 140     __ cmpb(Address(rthread, JavaThread::interp_only_mode_offset()), 0);
 141     __ jccb(Assembler::zero, run_compiled_code);
 142     __ jmp(Address(method, Method::interpreter_entry_offset()));
 143     __ BIND(run_compiled_code);
 144   }
 145 
 146   const ByteSize entry_offset = for_compiler_entry ? Method::from_compiled_offset() :
 147                                                      Method::from_interpreted_offset();
 148   __ jmp(Address(method, entry_offset));
 149 
 150   __ bind(L_no_such_method);
 151   __ jump(RuntimeAddress(StubRoutines::throw_AbstractMethodError_entry()));
 152 }
 153 
 154 void MethodHandles::jump_to_lambda_form(MacroAssembler* _masm,
 155                                         Register recv, Register method_temp,
 156                                         Register temp2,
 157                                         bool for_compiler_entry) {
 158   BLOCK_COMMENT("jump_to_lambda_form {");
 159   // This is the initial entry point of a lazy method handle.
 160   // After type checking, it picks up the invoker from the LambdaForm.
 161   assert_different_registers(recv, method_temp, temp2);
 162   assert(recv != noreg, "required register");
 163   assert(method_temp == rbx, "required register for loading method");
 164 
 165   //NOT_PRODUCT({ FlagSetting fs(TraceMethodHandles, true); trace_method_handle(_masm, "LZMH"); });
 166 
 167   // Load the invoker, as MH -> MH.form -> LF.vmentry
 168   oopDesc::bs()->interpreter_read_barrier(_masm, recv);
 169   __ verify_oop(recv);
 170   __ load_heap_oop(method_temp, Address(recv, NONZERO(java_lang_invoke_MethodHandle::form_offset_in_bytes())));
 171   oopDesc::bs()->interpreter_read_barrier(_masm, method_temp);
 172   __ verify_oop(method_temp);
 173   __ load_heap_oop(method_temp, Address(method_temp, NONZERO(java_lang_invoke_LambdaForm::vmentry_offset_in_bytes())));
 174   __ verify_oop(method_temp);
 175   // the following assumes that a Method* is normally compressed in the vmtarget field:
 176   __ movptr(method_temp, Address(method_temp, NONZERO(java_lang_invoke_MemberName::vmtarget_offset_in_bytes())));
 177 
 178   if (VerifyMethodHandles && !for_compiler_entry) {
 179     // make sure recv is already on stack
 180     __ movptr(temp2, Address(method_temp, Method::const_offset()));
 181     __ load_sized_value(temp2,
 182                         Address(temp2, ConstMethod::size_of_parameters_offset()),
 183                         sizeof(u2), /*is_signed*/ false);
 184     // assert(sizeof(u2) == sizeof(Method::_size_of_parameters), "");
 185     __ movptr(temp2, __ argument_address(temp2, -1));
 186     oopDesc::bs()->interpreter_read_barrier(_masm, temp2);
 187     Label L;
 188     __ cmpptr(recv, temp2);
 189     __ jcc(Assembler::equal, L);
 190     __ movptr(rax, temp2);
 191     __ STOP("receiver not on stack");
 192     __ BIND(L);
 193   }
 194 
 195   jump_from_method_handle(_masm, method_temp, temp2, for_compiler_entry);
 196   BLOCK_COMMENT("} jump_to_lambda_form");
 197 }
 198 
 199 
 200 // Code generation
 201 address MethodHandles::generate_method_handle_interpreter_entry(MacroAssembler* _masm,
 202                                                                 vmIntrinsics::ID iid) {
 203   const bool not_for_compiler_entry = false;  // this is the interpreter entry
 204   assert(is_signature_polymorphic(iid), "expected invoke iid");
 205   if (iid == vmIntrinsics::_invokeGeneric ||
 206       iid == vmIntrinsics::_compiledLambdaForm) {
 207     // Perhaps surprisingly, the symbolic references visible to Java are not directly used.
 208     // They are linked to Java-generated adapters via MethodHandleNatives.linkMethod.
 209     // They all allow an appendix argument.
 210     __ hlt();           // empty stubs make SG sick
 211     return NULL;
 212   }
 213 
 214   // rsi/r13: sender SP (must preserve; see prepare_to_jump_from_interpreted)
 215   // rbx: Method*
 216   // rdx: argument locator (parameter slot count, added to rsp)
 217   // rcx: used as temp to hold mh or receiver
 218   // rax, rdi: garbage temps, blown away
 219   Register rdx_argp   = rdx;   // argument list ptr, live on error paths
 220   Register rax_temp   = rax;
 221   Register rcx_mh     = rcx;   // MH receiver; dies quickly and is recycled
 222   Register rbx_method = rbx;   // eventual target of this invocation
 223 
 224   // here's where control starts out:
 225   __ align(CodeEntryAlignment);
 226   address entry_point = __ pc();
 227 
 228   if (VerifyMethodHandles) {
 229     Label L;
 230     BLOCK_COMMENT("verify_intrinsic_id {");
 231     __ cmpb(Address(rbx_method, Method::intrinsic_id_offset_in_bytes()), (int) iid);
 232     __ jcc(Assembler::equal, L);
 233     if (iid == vmIntrinsics::_linkToVirtual ||
 234         iid == vmIntrinsics::_linkToSpecial) {
 235       // could do this for all kinds, but would explode assembly code size
 236       trace_method_handle(_masm, "bad Method*::intrinsic_id");
 237     }
 238     __ STOP("bad Method*::intrinsic_id");
 239     __ bind(L);
 240     BLOCK_COMMENT("} verify_intrinsic_id");
 241   }
 242 
 243   // First task:  Find out how big the argument list is.
 244   Address rdx_first_arg_addr;
 245   int ref_kind = signature_polymorphic_intrinsic_ref_kind(iid);
 246   assert(ref_kind != 0 || iid == vmIntrinsics::_invokeBasic, "must be _invokeBasic or a linkTo intrinsic");
 247   if (ref_kind == 0 || MethodHandles::ref_kind_has_receiver(ref_kind)) {
 248     __ movptr(rdx_argp, Address(rbx_method, Method::const_offset()));
 249     __ load_sized_value(rdx_argp,
 250                         Address(rdx_argp, ConstMethod::size_of_parameters_offset()),
 251                         sizeof(u2), /*is_signed*/ false);
 252     // assert(sizeof(u2) == sizeof(Method::_size_of_parameters), "");
 253     rdx_first_arg_addr = __ argument_address(rdx_argp, -1);
 254   } else {
 255     DEBUG_ONLY(rdx_argp = noreg);
 256   }
 257 
 258   if (!is_signature_polymorphic_static(iid)) {
 259     __ movptr(rcx_mh, rdx_first_arg_addr);
 260     DEBUG_ONLY(rdx_argp = noreg);
 261   }
 262 
 263   // rdx_first_arg_addr is live!
 264 
 265   trace_method_handle_interpreter_entry(_masm, iid);
 266 
 267   if (iid == vmIntrinsics::_invokeBasic) {
 268     generate_method_handle_dispatch(_masm, iid, rcx_mh, noreg, not_for_compiler_entry);
 269 
 270   } else {
 271     // Adjust argument list by popping the trailing MemberName argument.
 272     Register rcx_recv = noreg;
 273     if (MethodHandles::ref_kind_has_receiver(ref_kind)) {
 274       // Load the receiver (not the MH; the actual MemberName's receiver) up from the interpreter stack.
 275       __ movptr(rcx_recv = rcx, rdx_first_arg_addr);
 276     }
 277     DEBUG_ONLY(rdx_argp = noreg);
 278     Register rbx_member = rbx_method;  // MemberName ptr; incoming method ptr is dead now
 279     __ pop(rax_temp);           // return address
 280     __ pop(rbx_member);         // extract last argument
 281     __ push(rax_temp);          // re-push return address
 282     generate_method_handle_dispatch(_masm, iid, rcx_recv, rbx_member, not_for_compiler_entry);
 283   }
 284 
 285   return entry_point;
 286 }
 287 
 288 void MethodHandles::generate_method_handle_dispatch(MacroAssembler* _masm,
 289                                                     vmIntrinsics::ID iid,
 290                                                     Register receiver_reg,
 291                                                     Register member_reg,
 292                                                     bool for_compiler_entry) {
 293   assert(is_signature_polymorphic(iid), "expected invoke iid");
 294   Register rbx_method = rbx;   // eventual target of this invocation
 295   // temps used in this code are not used in *either* compiled or interpreted calling sequences
 296 #ifdef _LP64
 297   Register temp1 = rscratch1;
 298   Register temp2 = rscratch2;
 299   Register temp3 = rax;
 300   if (for_compiler_entry) {
 301     assert(receiver_reg == (iid == vmIntrinsics::_linkToStatic ? noreg : j_rarg0), "only valid assignment");
 302     assert_different_registers(temp1,        j_rarg0, j_rarg1, j_rarg2, j_rarg3, j_rarg4, j_rarg5);
 303     assert_different_registers(temp2,        j_rarg0, j_rarg1, j_rarg2, j_rarg3, j_rarg4, j_rarg5);
 304     assert_different_registers(temp3,        j_rarg0, j_rarg1, j_rarg2, j_rarg3, j_rarg4, j_rarg5);
 305   }
 306 #else
 307   Register temp1 = (for_compiler_entry ? rsi : rdx);
 308   Register temp2 = rdi;
 309   Register temp3 = rax;
 310   if (for_compiler_entry) {
 311     assert(receiver_reg == (iid == vmIntrinsics::_linkToStatic ? noreg : rcx), "only valid assignment");
 312     assert_different_registers(temp1,        rcx, rdx);
 313     assert_different_registers(temp2,        rcx, rdx);
 314     assert_different_registers(temp3,        rcx, rdx);
 315   }
 316 #endif
 317   else {
 318     assert_different_registers(temp1, temp2, temp3, saved_last_sp_register());  // don't trash lastSP
 319   }
 320   assert_different_registers(temp1, temp2, temp3, receiver_reg);
 321   assert_different_registers(temp1, temp2, temp3, member_reg);
 322 
 323   if (iid == vmIntrinsics::_invokeBasic) {
 324     // indirect through MH.form.vmentry.vmtarget
 325     jump_to_lambda_form(_masm, receiver_reg, rbx_method, temp1, for_compiler_entry);
 326 
 327   } else {
 328     // The method is a member invoker used by direct method handles.
 329     if (VerifyMethodHandles) {
 330       // make sure the trailing argument really is a MemberName (caller responsibility)
 331       verify_klass(_masm, member_reg, SystemDictionary::WK_KLASS_ENUM_NAME(java_lang_invoke_MemberName),
 332                    "MemberName required for invokeVirtual etc.");
 333     }
 334 
 335     Address member_clazz(    member_reg, NONZERO(java_lang_invoke_MemberName::clazz_offset_in_bytes()));
 336     Address member_vmindex(  member_reg, NONZERO(java_lang_invoke_MemberName::vmindex_offset_in_bytes()));
 337     Address member_vmtarget( member_reg, NONZERO(java_lang_invoke_MemberName::vmtarget_offset_in_bytes()));
 338 
 339     Register temp1_recv_klass = temp1;
 340     if (iid != vmIntrinsics::_linkToStatic) {
 341       __ verify_oop(receiver_reg);
 342       if (iid == vmIntrinsics::_linkToSpecial) {
 343         // Don't actually load the klass; just null-check the receiver.
 344         __ null_check(receiver_reg);
 345       } else {
 346         // load receiver klass itself
 347         __ null_check(receiver_reg, oopDesc::klass_offset_in_bytes());
 348         __ load_klass(temp1_recv_klass, receiver_reg);
 349         __ verify_klass_ptr(temp1_recv_klass);
 350       }
 351       BLOCK_COMMENT("check_receiver {");
 352       // The receiver for the MemberName must be in receiver_reg.
 353       // Check the receiver against the MemberName.clazz
 354       if (VerifyMethodHandles && iid == vmIntrinsics::_linkToSpecial) {
 355         // Did not load it above...
 356         __ load_klass(temp1_recv_klass, receiver_reg);
 357         __ verify_klass_ptr(temp1_recv_klass);
 358       }
 359       if (VerifyMethodHandles && iid != vmIntrinsics::_linkToInterface) {
 360         Label L_ok;
 361         Register temp2_defc = temp2;
 362         __ load_heap_oop(temp2_defc, member_clazz);
 363         load_klass_from_Class(_masm, temp2_defc);
 364         __ verify_klass_ptr(temp2_defc);
 365         __ check_klass_subtype(temp1_recv_klass, temp2_defc, temp3, L_ok);
 366         // If we get here, the type check failed!
 367         __ STOP("receiver class disagrees with MemberName.clazz");
 368         __ bind(L_ok);
 369       }
 370       BLOCK_COMMENT("} check_receiver");
 371     }
 372     if (iid == vmIntrinsics::_linkToSpecial ||
 373         iid == vmIntrinsics::_linkToStatic) {
 374       DEBUG_ONLY(temp1_recv_klass = noreg);  // these guys didn't load the recv_klass
 375     }
 376 
 377     // Live registers at this point:
 378     //  member_reg - MemberName that was the trailing argument
 379     //  temp1_recv_klass - klass of stacked receiver, if needed
 380     //  rsi/r13 - interpreter linkage (if interpreted)
 381     //  rcx, rdx, rsi, rdi, r8 - compiler arguments (if compiled)
 382 
 383     oopDesc::bs()->interpreter_read_barrier(_masm, member_reg);
 384     Label L_incompatible_class_change_error;
 385     switch (iid) {
 386     case vmIntrinsics::_linkToSpecial:
 387       if (VerifyMethodHandles) {
 388         verify_ref_kind(_masm, JVM_REF_invokeSpecial, member_reg, temp3);
 389       }
 390       __ movptr(rbx_method, member_vmtarget);
 391       break;
 392 
 393     case vmIntrinsics::_linkToStatic:
 394       if (VerifyMethodHandles) {
 395         verify_ref_kind(_masm, JVM_REF_invokeStatic, member_reg, temp3);
 396       }
 397       __ movptr(rbx_method, member_vmtarget);
 398       break;
 399 
 400     case vmIntrinsics::_linkToVirtual:
 401     {
 402       // same as TemplateTable::invokevirtual,
 403       // minus the CP setup and profiling:
 404 
 405       if (VerifyMethodHandles) {
 406         verify_ref_kind(_masm, JVM_REF_invokeVirtual, member_reg, temp3);
 407       }
 408 
 409       // pick out the vtable index from the MemberName, and then we can discard it:
 410       Register temp2_index = temp2;
 411       __ movptr(temp2_index, member_vmindex);
 412 
 413       if (VerifyMethodHandles) {
 414         Label L_index_ok;
 415         __ cmpl(temp2_index, 0);
 416         __ jcc(Assembler::greaterEqual, L_index_ok);
 417         __ STOP("no virtual index");
 418         __ BIND(L_index_ok);
 419       }
 420 
 421       // Note:  The verifier invariants allow us to ignore MemberName.clazz and vmtarget
 422       // at this point.  And VerifyMethodHandles has already checked clazz, if needed.
 423 
 424       // get target Method* & entry point
 425       __ lookup_virtual_method(temp1_recv_klass, temp2_index, rbx_method);
 426       break;
 427     }
 428 
 429     case vmIntrinsics::_linkToInterface:
 430     {
 431       // same as TemplateTable::invokeinterface
 432       // (minus the CP setup and profiling, with different argument motion)
 433       if (VerifyMethodHandles) {
 434         verify_ref_kind(_masm, JVM_REF_invokeInterface, member_reg, temp3);
 435       }
 436 
 437       Register temp3_intf = temp3;
 438       __ load_heap_oop(temp3_intf, member_clazz);
 439       load_klass_from_Class(_masm, temp3_intf);
 440       __ verify_klass_ptr(temp3_intf);
 441 
 442       Register rbx_index = rbx_method;
 443       __ movptr(rbx_index, member_vmindex);
 444       if (VerifyMethodHandles) {
 445         Label L;
 446         __ cmpl(rbx_index, 0);
 447         __ jcc(Assembler::greaterEqual, L);
 448         __ STOP("invalid vtable index for MH.invokeInterface");
 449         __ bind(L);
 450       }
 451 
 452       // given intf, index, and recv klass, dispatch to the implementation method
 453       __ lookup_interface_method(temp1_recv_klass, temp3_intf,
 454                                  // note: next two args must be the same:
 455                                  rbx_index, rbx_method,
 456                                  temp2,
 457                                  L_incompatible_class_change_error);
 458       break;
 459     }
 460 
 461     default:
 462       fatal(err_msg_res("unexpected intrinsic %d: %s", iid, vmIntrinsics::name_at(iid)));
 463       break;
 464     }
 465 
 466     // Live at this point:
 467     //   rbx_method
 468     //   rsi/r13 (if interpreted)
 469 
 470     // After figuring out which concrete method to call, jump into it.
 471     // Note that this works in the interpreter with no data motion.
 472     // But the compiled version will require that rcx_recv be shifted out.
 473     __ verify_method_ptr(rbx_method);
 474     jump_from_method_handle(_masm, rbx_method, temp1, for_compiler_entry);
 475 
 476     if (iid == vmIntrinsics::_linkToInterface) {
 477       __ bind(L_incompatible_class_change_error);
 478       __ jump(RuntimeAddress(StubRoutines::throw_IncompatibleClassChangeError_entry()));
 479     }
 480   }
 481 }
 482 
 483 #ifndef PRODUCT
 484 void trace_method_handle_stub(const char* adaptername,
 485                               oop mh,
 486                               intptr_t* saved_regs,
 487                               intptr_t* entry_sp) {
 488   // called as a leaf from native code: do not block the JVM!
 489   bool has_mh = (strstr(adaptername, "/static") == NULL &&
 490                  strstr(adaptername, "linkTo") == NULL);    // static linkers don't have MH
 491   const char* mh_reg_name = has_mh ? "rcx_mh" : "rcx";
 492   tty->print_cr("MH %s %s=" PTR_FORMAT " sp=" PTR_FORMAT,
 493                 adaptername, mh_reg_name,
 494                 (void *)mh, entry_sp);
 495 
 496   if (Verbose) {
 497     tty->print_cr("Registers:");
 498     const int saved_regs_count = RegisterImpl::number_of_registers;
 499     for (int i = 0; i < saved_regs_count; i++) {
 500       Register r = as_Register(i);
 501       // The registers are stored in reverse order on the stack (by pusha).
 502       tty->print("%3s=" PTR_FORMAT, r->name(), saved_regs[((saved_regs_count - 1) - i)]);
 503       if ((i + 1) % 4 == 0) {
 504         tty->cr();
 505       } else {
 506         tty->print(", ");
 507       }
 508     }
 509     tty->cr();
 510 
 511     {
 512      // dumping last frame with frame::describe
 513 
 514       JavaThread* p = JavaThread::active();
 515 
 516       ResourceMark rm;
 517       PRESERVE_EXCEPTION_MARK; // may not be needed by safer and unexpensive here
 518       FrameValues values;
 519 
 520       // Note: We want to allow trace_method_handle from any call site.
 521       // While trace_method_handle creates a frame, it may be entered
 522       // without a PC on the stack top (e.g. not just after a call).
 523       // Walking that frame could lead to failures due to that invalid PC.
 524       // => carefully detect that frame when doing the stack walking
 525 
 526       // Current C frame
 527       frame cur_frame = os::current_frame();
 528 
 529       // Robust search of trace_calling_frame (independant of inlining).
 530       // Assumes saved_regs comes from a pusha in the trace_calling_frame.
 531       assert(cur_frame.sp() < saved_regs, "registers not saved on stack ?");
 532       frame trace_calling_frame = os::get_sender_for_C_frame(&cur_frame);
 533       while (trace_calling_frame.fp() < saved_regs) {
 534         trace_calling_frame = os::get_sender_for_C_frame(&trace_calling_frame);
 535       }
 536 
 537       // safely create a frame and call frame::describe
 538       intptr_t *dump_sp = trace_calling_frame.sender_sp();
 539       intptr_t *dump_fp = trace_calling_frame.link();
 540 
 541       bool walkable = has_mh; // whether the traced frame shoud be walkable
 542 
 543       if (walkable) {
 544         // The previous definition of walkable may have to be refined
 545         // if new call sites cause the next frame constructor to start
 546         // failing. Alternatively, frame constructors could be
 547         // modified to support the current or future non walkable
 548         // frames (but this is more intrusive and is not considered as
 549         // part of this RFE, which will instead use a simpler output).
 550         frame dump_frame = frame(dump_sp, dump_fp);
 551         dump_frame.describe(values, 1);
 552       } else {
 553         // Stack may not be walkable (invalid PC above FP):
 554         // Add descriptions without building a Java frame to avoid issues
 555         values.describe(-1, dump_fp, "fp for #1 <not parsed, cannot trust pc>");
 556         values.describe(-1, dump_sp, "sp for #1");
 557       }
 558       values.describe(-1, entry_sp, "raw top of stack");
 559 
 560       tty->print_cr("Stack layout:");
 561       values.print(p);
 562     }
 563     if (has_mh && mh->is_oop()) {
 564       mh->print();
 565       if (java_lang_invoke_MethodHandle::is_instance(mh)) {
 566         if (java_lang_invoke_MethodHandle::form_offset_in_bytes() != 0)
 567           java_lang_invoke_MethodHandle::form(mh)->print();
 568       }
 569     }
 570   }
 571 }
 572 
 573 // The stub wraps the arguments in a struct on the stack to avoid
 574 // dealing with the different calling conventions for passing 6
 575 // arguments.
 576 struct MethodHandleStubArguments {
 577   const char* adaptername;
 578   oopDesc* mh;
 579   intptr_t* saved_regs;
 580   intptr_t* entry_sp;
 581 };
 582 void trace_method_handle_stub_wrapper(MethodHandleStubArguments* args) {
 583   trace_method_handle_stub(args->adaptername,
 584                            args->mh,
 585                            args->saved_regs,
 586                            args->entry_sp);
 587 }
 588 
 589 void MethodHandles::trace_method_handle(MacroAssembler* _masm, const char* adaptername) {
 590   if (!TraceMethodHandles)  return;
 591   BLOCK_COMMENT("trace_method_handle {");
 592   __ enter();
 593   __ andptr(rsp, -16); // align stack if needed for FPU state
 594   __ pusha();
 595   __ mov(rbx, rsp); // for retreiving saved_regs
 596   // Note: saved_regs must be in the entered frame for the
 597   // robust stack walking implemented in trace_method_handle_stub.
 598 
 599   // save FP result, valid at some call sites (adapter_opt_return_float, ...)
 600   __ increment(rsp, -2 * wordSize);
 601   if  (UseSSE >= 2) {
 602     __ movdbl(Address(rsp, 0), xmm0);
 603   } else if (UseSSE == 1) {
 604     __ movflt(Address(rsp, 0), xmm0);
 605   } else {
 606     __ fst_d(Address(rsp, 0));
 607   }
 608 
 609   // Incoming state:
 610   // rcx: method handle
 611   //
 612   // To avoid calling convention issues, build a record on the stack
 613   // and pass the pointer to that instead.
 614   __ push(rbp);               // entry_sp (with extra align space)
 615   __ push(rbx);               // pusha saved_regs
 616   __ push(rcx);               // mh
 617   __ push(rcx);               // slot for adaptername
 618   __ movptr(Address(rsp, 0), (intptr_t) adaptername);
 619   __ super_call_VM_leaf(CAST_FROM_FN_PTR(address, trace_method_handle_stub_wrapper), rsp);
 620   __ increment(rsp, sizeof(MethodHandleStubArguments));
 621 
 622   if  (UseSSE >= 2) {
 623     __ movdbl(xmm0, Address(rsp, 0));
 624   } else if (UseSSE == 1) {
 625     __ movflt(xmm0, Address(rsp, 0));
 626   } else {
 627     __ fld_d(Address(rsp, 0));
 628   }
 629   __ increment(rsp, 2 * wordSize);
 630 
 631   __ popa();
 632   __ leave();
 633   BLOCK_COMMENT("} trace_method_handle");
 634 }
 635 #endif //PRODUCT