src/hotspot/cpu/riscv/sharedRuntime_riscv.cpp

/*
 * Copyright (c) 2003, 2025, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2014, 2020, Red Hat Inc. All rights reserved.
 * Copyright (c) 2020, 2023, Huawei Technologies Co., Ltd. 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 "asm/macroAssembler.hpp"
#include "asm/macroAssembler.inline.hpp"
#include "code/compiledIC.hpp"
#include "code/debugInfoRec.hpp"
#include "code/vtableStubs.hpp"
#include "compiler/oopMap.hpp"
#include "gc/shared/barrierSetAssembler.hpp"
#include "interpreter/interp_masm.hpp"
#include "interpreter/interpreter.hpp"
#include "logging/log.hpp"
#include "memory/resourceArea.hpp"
#include "nativeInst_riscv.hpp"
#include "oops/klass.inline.hpp"
#include "oops/method.inline.hpp"
#include "prims/methodHandles.hpp"
#include "runtime/continuation.hpp"
#include "runtime/continuationEntry.inline.hpp"
#include "runtime/globals.hpp"
#include "runtime/jniHandles.hpp"
#include "runtime/safepointMechanism.hpp"
#include "runtime/sharedRuntime.hpp"
#include "runtime/signature.hpp"
#include "runtime/stubRoutines.hpp"
#include "runtime/timerTrace.hpp"
#include "runtime/vframeArray.hpp"
#include "utilities/align.hpp"
#include "utilities/formatBuffer.hpp"
#include "vmreg_riscv.inline.hpp"
#ifdef COMPILER1
#include "c1/c1_Runtime1.hpp"
#endif
#ifdef COMPILER2
#include "adfiles/ad_riscv.hpp"
#include "opto/runtime.hpp"
#endif
#if INCLUDE_JVMCI
#include "jvmci/jvmciJavaClasses.hpp"
#endif

#define __ masm->

#ifdef PRODUCT
#define BLOCK_COMMENT(str) /* nothing */
#else
#define BLOCK_COMMENT(str) __ block_comment(str)
#endif

const int StackAlignmentInSlots = StackAlignmentInBytes / VMRegImpl::stack_slot_size;

class RegisterSaver {
  const bool _save_vectors;
 public:
  RegisterSaver(bool save_vectors) : _save_vectors(UseRVV && save_vectors) {}
  ~RegisterSaver() {}
  OopMap* save_live_registers(MacroAssembler* masm, int additional_frame_words, int* total_frame_words);
  void restore_live_registers(MacroAssembler* masm);

  // Offsets into the register save area
  // Used by deoptimization when it is managing result register
  // values on its own
  // gregs:28, float_register:32; except: x1(ra) & x2(sp) & gp(x3) & tp(x4)
  // |---v0---|<---SP
  // |---v1---|save vectors only in generate_handler_blob
  // |-- .. --|
  // |---v31--|-----
  // |---f0---|
  // |---f1---|
  // |   ..   |
  // |---f31--|
  // |---reserved slot for stack alignment---|
  // |---x5---|
  // |   x6   |
  // |---.. --|
  // |---x31--|
  // |---fp---|
  // |---ra---|
  int v0_offset_in_bytes(void) { return 0; }
  int f0_offset_in_bytes(void) {
    int f0_offset = 0;
#ifdef COMPILER2
    if (_save_vectors) {
      f0_offset += Matcher::scalable_vector_reg_size(T_INT) * VectorRegister::number_of_registers *
                   BytesPerInt;
    }
#endif
    return f0_offset;
  }
  int reserved_slot_offset_in_bytes(void) {
    return f0_offset_in_bytes() +
           FloatRegister::max_slots_per_register *
           FloatRegister::number_of_registers *
           BytesPerInt;
  }

  int reg_offset_in_bytes(Register r) {
    assert (r->encoding() > 4, "ra, sp, gp and tp not saved");
    return reserved_slot_offset_in_bytes() + (r->encoding() - 4 /* x1, x2, x3, x4 */) * wordSize;
  }

  int freg_offset_in_bytes(FloatRegister f) {
    return f0_offset_in_bytes() + f->encoding() * wordSize;
  }

  int ra_offset_in_bytes(void) {
    return reserved_slot_offset_in_bytes() +
           (Register::number_of_registers - 3) *
           Register::max_slots_per_register *
           BytesPerInt;
  }
};

OopMap* RegisterSaver::save_live_registers(MacroAssembler* masm, int additional_frame_words, int* total_frame_words) {
  int vector_size_in_bytes = 0;
  int vector_size_in_slots = 0;
#ifdef COMPILER2
  if (_save_vectors) {
    vector_size_in_bytes += Matcher::scalable_vector_reg_size(T_BYTE);
    vector_size_in_slots += Matcher::scalable_vector_reg_size(T_INT);
  }
#endif

  int frame_size_in_bytes = align_up(additional_frame_words * wordSize + ra_offset_in_bytes() + wordSize, 16);
  // OopMap frame size is in compiler stack slots (jint's) not bytes or words
  int frame_size_in_slots = frame_size_in_bytes / BytesPerInt;
  // The caller will allocate additional_frame_words
  int additional_frame_slots = additional_frame_words * wordSize / BytesPerInt;
  // CodeBlob frame size is in words.
  int frame_size_in_words = frame_size_in_bytes / wordSize;
  *total_frame_words = frame_size_in_words;

  // Save Integer, Float and Vector registers.
  __ enter();
  __ push_CPU_state(_save_vectors, vector_size_in_bytes);

  // Set an oopmap for the call site.  This oopmap will map all
  // oop-registers and debug-info registers as callee-saved.  This
  // will allow deoptimization at this safepoint to find all possible
  // debug-info recordings, as well as let GC find all oops.

  OopMapSet *oop_maps = new OopMapSet();
  OopMap* oop_map = new OopMap(frame_size_in_slots, 0);
  assert_cond(oop_maps != nullptr && oop_map != nullptr);

  int sp_offset_in_slots = 0;
  int step_in_slots = 0;
  if (_save_vectors) {
    step_in_slots = vector_size_in_slots;
    for (int i = 0; i < VectorRegister::number_of_registers; i++, sp_offset_in_slots += step_in_slots) {
      VectorRegister r = as_VectorRegister(i);
      oop_map->set_callee_saved(VMRegImpl::stack2reg(sp_offset_in_slots), r->as_VMReg());
    }
  }

  step_in_slots = FloatRegister::max_slots_per_register;
  for (int i = 0; i < FloatRegister::number_of_registers; i++, sp_offset_in_slots += step_in_slots) {
    FloatRegister r = as_FloatRegister(i);
    oop_map->set_callee_saved(VMRegImpl::stack2reg(sp_offset_in_slots), r->as_VMReg());
  }

  step_in_slots = Register::max_slots_per_register;
  // skip the slot reserved for alignment, see MacroAssembler::push_reg;
  // also skip x5 ~ x6 on the stack because they are caller-saved registers.
  sp_offset_in_slots += Register::max_slots_per_register * 3;
  // besides, we ignore x0 ~ x4 because push_CPU_state won't push them on the stack.
  for (int i = 7; i < Register::number_of_registers; i++, sp_offset_in_slots += step_in_slots) {
    Register r = as_Register(i);
    if (r != xthread) {
      oop_map->set_callee_saved(VMRegImpl::stack2reg(sp_offset_in_slots + additional_frame_slots), r->as_VMReg());
    }
  }

  return oop_map;
}

void RegisterSaver::restore_live_registers(MacroAssembler* masm) {
#ifdef COMPILER2
  __ pop_CPU_state(_save_vectors, Matcher::scalable_vector_reg_size(T_BYTE));
#else
#if !INCLUDE_JVMCI
  assert(!_save_vectors, "vectors are generated only by C2 and JVMCI");
#endif
  __ pop_CPU_state(_save_vectors);
#endif
  __ leave();
}

// Is vector's size (in bytes) bigger than a size saved by default?
// riscv does not ovlerlay the floating-point registers on vector registers like aarch64.
bool SharedRuntime::is_wide_vector(int size) {
  return UseRVV;
}

// ---------------------------------------------------------------------------
// Read the array of BasicTypes from a signature, and compute where the
// arguments should go.  Values in the VMRegPair regs array refer to 4-byte
// quantities.  Values less than VMRegImpl::stack0 are registers, those above
// refer to 4-byte stack slots.  All stack slots are based off of the stack pointer
// as framesizes are fixed.
// VMRegImpl::stack0 refers to the first slot 0(sp).
// and VMRegImpl::stack0+1 refers to the memory word 4-byes higher.
// Register up to Register::number_of_registers) are the 64-bit
// integer registers.

// Note: the INPUTS in sig_bt are in units of Java argument words,
// which are 64-bit.  The OUTPUTS are in 32-bit units.

// The Java calling convention is a "shifted" version of the C ABI.
// By skipping the first C ABI register we can call non-static jni
// methods with small numbers of arguments without having to shuffle
// the arguments at all. Since we control the java ABI we ought to at
// least get some advantage out of it.

int SharedRuntime::java_calling_convention(const BasicType *sig_bt,
                                           VMRegPair *regs,
                                           int total_args_passed) {
  // Create the mapping between argument positions and
  // registers.
  static const Register INT_ArgReg[Argument::n_int_register_parameters_j] = {
    j_rarg0, j_rarg1, j_rarg2, j_rarg3,
    j_rarg4, j_rarg5, j_rarg6, j_rarg7
  };
  static const FloatRegister FP_ArgReg[Argument::n_float_register_parameters_j] = {
    j_farg0, j_farg1, j_farg2, j_farg3,
    j_farg4, j_farg5, j_farg6, j_farg7
  };

  uint int_args = 0;
  uint fp_args = 0;
  uint stk_args = 0;

  for (int i = 0; i < total_args_passed; i++) {
    switch (sig_bt[i]) {
      case T_BOOLEAN: // fall through
      case T_CHAR:    // fall through
      case T_BYTE:    // fall through
      case T_SHORT:   // fall through
      case T_INT:
        if (int_args < Argument::n_int_register_parameters_j) {
          regs[i].set1(INT_ArgReg[int_args++]->as_VMReg());
        } else {
          stk_args = align_up(stk_args, 2);
          regs[i].set1(VMRegImpl::stack2reg(stk_args));
          stk_args += 1;
        }
        break;
      case T_VOID:
        // halves of T_LONG or T_DOUBLE
        assert(i != 0 && (sig_bt[i - 1] == T_LONG || sig_bt[i - 1] == T_DOUBLE), "expecting half");
        regs[i].set_bad();
        break;
      case T_LONG:      // fall through
        assert((i + 1) < total_args_passed && sig_bt[i + 1] == T_VOID, "expecting half");
      case T_OBJECT:    // fall through
      case T_ARRAY:     // fall through
      case T_ADDRESS:
        if (int_args < Argument::n_int_register_parameters_j) {
          regs[i].set2(INT_ArgReg[int_args++]->as_VMReg());
        } else {
          stk_args = align_up(stk_args, 2);
          regs[i].set2(VMRegImpl::stack2reg(stk_args));
          stk_args += 2;
        }
        break;
      case T_FLOAT:
        if (fp_args < Argument::n_float_register_parameters_j) {
          regs[i].set1(FP_ArgReg[fp_args++]->as_VMReg());
        } else {
          stk_args = align_up(stk_args, 2);
          regs[i].set1(VMRegImpl::stack2reg(stk_args));
          stk_args += 1;
        }
        break;
      case T_DOUBLE:
        assert((i + 1) < total_args_passed && sig_bt[i + 1] == T_VOID, "expecting half");
        if (fp_args < Argument::n_float_register_parameters_j) {
          regs[i].set2(FP_ArgReg[fp_args++]->as_VMReg());
        } else {
          stk_args = align_up(stk_args, 2);
          regs[i].set2(VMRegImpl::stack2reg(stk_args));
          stk_args += 2;
        }
        break;
      default:
        ShouldNotReachHere();
    }
  }

  return stk_args;
}

// Patch the callers callsite with entry to compiled code if it exists.
static void patch_callers_callsite(MacroAssembler *masm) {
  Label L;
  __ ld(t0, Address(xmethod, in_bytes(Method::code_offset())));
  __ beqz(t0, L);

  __ enter();
  __ push_CPU_state();

  // VM needs caller's callsite
  // VM needs target method
  // This needs to be a long call since we will relocate this adapter to
  // the codeBuffer and it may not reach

#ifndef PRODUCT
  assert(frame::arg_reg_save_area_bytes == 0, "not expecting frame reg save area");
#endif

  __ mv(c_rarg0, xmethod);
  __ mv(c_rarg1, ra);
  __ rt_call(CAST_FROM_FN_PTR(address, SharedRuntime::fixup_callers_callsite));

  __ pop_CPU_state();
  // restore sp
  __ leave();
  __ bind(L);
}

static void gen_c2i_adapter(MacroAssembler *masm,
                            int total_args_passed,
                            int comp_args_on_stack,
                            const BasicType *sig_bt,
                            const VMRegPair *regs,
                            Label& skip_fixup) {
  // Before we get into the guts of the C2I adapter, see if we should be here
  // at all.  We've come from compiled code and are attempting to jump to the
  // interpreter, which means the caller made a static call to get here
  // (vcalls always get a compiled target if there is one).  Check for a
  // compiled target.  If there is one, we need to patch the caller's call.
  patch_callers_callsite(masm);

  __ bind(skip_fixup);

  int words_pushed = 0;

  // Since all args are passed on the stack, total_args_passed *
  // Interpreter::stackElementSize is the space we need.

  int extraspace = total_args_passed * Interpreter::stackElementSize;

  __ mv(x19_sender_sp, sp);

  // stack is aligned, keep it that way
  extraspace = align_up(extraspace, 2 * wordSize);

  if (extraspace) {
    __ sub(sp, sp, extraspace);
  }

  // Now write the args into the outgoing interpreter space
  for (int i = 0; i < total_args_passed; i++) {
    if (sig_bt[i] == T_VOID) {
      assert(i > 0 && (sig_bt[i - 1] == T_LONG || sig_bt[i - 1] == T_DOUBLE), "missing half");
      continue;
    }

    // offset to start parameters
    int st_off   = (total_args_passed - i - 1) * Interpreter::stackElementSize;
    int next_off = st_off - Interpreter::stackElementSize;

    // Say 4 args:
    // i   st_off
    // 0   32 T_LONG
    // 1   24 T_VOID
    // 2   16 T_OBJECT
    // 3    8 T_BOOL
    // -    0 return address
    //
    // However to make thing extra confusing. Because we can fit a Java long/double in
    // a single slot on a 64 bt vm and it would be silly to break them up, the interpreter
    // leaves one slot empty and only stores to a single slot. In this case the
    // slot that is occupied is the T_VOID slot. See I said it was confusing.

    VMReg r_1 = regs[i].first();
    VMReg r_2 = regs[i].second();
    if (!r_1->is_valid()) {
      assert(!r_2->is_valid(), "");
      continue;
    }
    if (r_1->is_stack()) {
      // memory to memory use t0
      int ld_off = (r_1->reg2stack() * VMRegImpl::stack_slot_size
                    + extraspace
                    + words_pushed * wordSize);
      if (!r_2->is_valid()) {
        __ lwu(t0, Address(sp, ld_off));
        __ sd(t0, Address(sp, st_off), /*temp register*/esp);
      } else {
        __ ld(t0, Address(sp, ld_off), /*temp register*/esp);

        // Two VMREgs|OptoRegs can be T_OBJECT, T_ADDRESS, T_DOUBLE, T_LONG
        // T_DOUBLE and T_LONG use two slots in the interpreter
        if (sig_bt[i] == T_LONG || sig_bt[i] == T_DOUBLE) {
          // ld_off == LSW, ld_off+wordSize == MSW
          // st_off == MSW, next_off == LSW
          __ sd(t0, Address(sp, next_off), /*temp register*/esp);
#ifdef ASSERT
          // Overwrite the unused slot with known junk
          __ mv(t0, 0xdeadffffdeadaaaaul);
          __ sd(t0, Address(sp, st_off), /*temp register*/esp);
#endif /* ASSERT */
        } else {
          __ sd(t0, Address(sp, st_off), /*temp register*/esp);
        }
      }
    } else if (r_1->is_Register()) {
      Register r = r_1->as_Register();
      if (!r_2->is_valid()) {
        // must be only an int (or less ) so move only 32bits to slot
        __ sd(r, Address(sp, st_off));
      } else {
        // Two VMREgs|OptoRegs can be T_OBJECT, T_ADDRESS, T_DOUBLE, T_LONG
        // T_DOUBLE and T_LONG use two slots in the interpreter
        if ( sig_bt[i] == T_LONG || sig_bt[i] == T_DOUBLE) {
          // long/double in gpr
#ifdef ASSERT
          // Overwrite the unused slot with known junk
          __ mv(t0, 0xdeadffffdeadaaabul);
          __ sd(t0, Address(sp, st_off), /*temp register*/esp);
#endif /* ASSERT */
          __ sd(r, Address(sp, next_off));
        } else {
          __ sd(r, Address(sp, st_off));
        }
      }
    } else {
      assert(r_1->is_FloatRegister(), "");
      if (!r_2->is_valid()) {
        // only a float use just part of the slot
        __ fsw(r_1->as_FloatRegister(), Address(sp, st_off));
      } else {
#ifdef ASSERT
        // Overwrite the unused slot with known junk
        __ mv(t0, 0xdeadffffdeadaaacul);
        __ sd(t0, Address(sp, st_off), /*temp register*/esp);
#endif /* ASSERT */
        __ fsd(r_1->as_FloatRegister(), Address(sp, next_off));
      }
    }
  }

  __ mv(esp, sp); // Interp expects args on caller's expression stack

  __ ld(t1, Address(xmethod, in_bytes(Method::interpreter_entry_offset())));
  __ jr(t1);
}

void SharedRuntime::gen_i2c_adapter(MacroAssembler *masm,
                                    int total_args_passed,
                                    int comp_args_on_stack,
                                    const BasicType *sig_bt,
                                    const VMRegPair *regs) {
  // Note: x19_sender_sp contains the senderSP on entry. We must
  // preserve it since we may do a i2c -> c2i transition if we lose a
  // race where compiled code goes non-entrant while we get args
  // ready.

  // Cut-out for having no stack args.
  int comp_words_on_stack = align_up(comp_args_on_stack * VMRegImpl::stack_slot_size, wordSize) >> LogBytesPerWord;
  if (comp_args_on_stack != 0) {
    __ sub(t0, sp, comp_words_on_stack * wordSize);
    __ andi(sp, t0, -16);
  }

  // Will jump to the compiled code just as if compiled code was doing it.
  // Pre-load the register-jump target early, to schedule it better.
  __ ld(t1, Address(xmethod, in_bytes(Method::from_compiled_offset())));

#if INCLUDE_JVMCI
  if (EnableJVMCI) {
    // check if this call should be routed towards a specific entry point
    __ ld(t0, Address(xthread, in_bytes(JavaThread::jvmci_alternate_call_target_offset())));
    Label no_alternative_target;
    __ beqz(t0, no_alternative_target);
    __ mv(t1, t0);
    __ sd(zr, Address(xthread, in_bytes(JavaThread::jvmci_alternate_call_target_offset())));
    __ bind(no_alternative_target);
  }
#endif // INCLUDE_JVMCI

  // Now generate the shuffle code.
  for (int i = 0; i < total_args_passed; i++) {
    if (sig_bt[i] == T_VOID) {
      assert(i > 0 && (sig_bt[i - 1] == T_LONG || sig_bt[i - 1] == T_DOUBLE), "missing half");
      continue;
    }

    // Pick up 0, 1 or 2 words from SP+offset.

    assert(!regs[i].second()->is_valid() || regs[i].first()->next() == regs[i].second(),
           "scrambled load targets?");
    // Load in argument order going down.
    int ld_off = (total_args_passed - i - 1) * Interpreter::stackElementSize;
    // Point to interpreter value (vs. tag)
    int next_off = ld_off - Interpreter::stackElementSize;

    VMReg r_1 = regs[i].first();
    VMReg r_2 = regs[i].second();
    if (!r_1->is_valid()) {
      assert(!r_2->is_valid(), "");
      continue;
    }
    if (r_1->is_stack()) {
      // Convert stack slot to an SP offset (+ wordSize to account for return address )
      int st_off = regs[i].first()->reg2stack() * VMRegImpl::stack_slot_size;
      if (!r_2->is_valid()) {
        __ lw(t0, Address(esp, ld_off));
        __ sd(t0, Address(sp, st_off), /*temp register*/t2);
      } else {
        //
        // We are using two optoregs. This can be either T_OBJECT,
        // T_ADDRESS, T_LONG, or T_DOUBLE the interpreter allocates
        // two slots but only uses one for thr T_LONG or T_DOUBLE case
        // So we must adjust where to pick up the data to match the
        // interpreter.
        //
        // Interpreter local[n] == MSW, local[n+1] == LSW however locals
        // are accessed as negative so LSW is at LOW address

        // ld_off is MSW so get LSW
        const int offset = (sig_bt[i] == T_LONG || sig_bt[i] == T_DOUBLE) ?
                           next_off : ld_off;
        __ ld(t0, Address(esp, offset));
        // st_off is LSW (i.e. reg.first())
        __ sd(t0, Address(sp, st_off), /*temp register*/t2);
      }
    } else if (r_1->is_Register()) {  // Register argument
      Register r = r_1->as_Register();
      if (r_2->is_valid()) {
        //
        // We are using two VMRegs. This can be either T_OBJECT,
        // T_ADDRESS, T_LONG, or T_DOUBLE the interpreter allocates
        // two slots but only uses one for thr T_LONG or T_DOUBLE case
        // So we must adjust where to pick up the data to match the
        // interpreter.

        const int offset = (sig_bt[i] == T_LONG || sig_bt[i] == T_DOUBLE) ?
                           next_off : ld_off;

        // this can be a misaligned move
        __ ld(r, Address(esp, offset));
      } else {
        // sign extend and use a full word?
        __ lw(r, Address(esp, ld_off));
      }
    } else {
      if (!r_2->is_valid()) {
        __ flw(r_1->as_FloatRegister(), Address(esp, ld_off));
      } else {
        __ fld(r_1->as_FloatRegister(), Address(esp, next_off));
      }
    }
  }

  __ push_cont_fastpath(xthread); // Set JavaThread::_cont_fastpath to the sp of the oldest interpreted frame we know about

  // 6243940 We might end up in handle_wrong_method if
  // the callee is deoptimized as we race thru here. If that
  // happens we don't want to take a safepoint because the
  // caller frame will look interpreted and arguments are now
  // "compiled" so it is much better to make this transition
  // invisible to the stack walking code. Unfortunately if
  // we try and find the callee by normal means a safepoint
  // is possible. So we stash the desired callee in the thread
  // and the vm will find there should this case occur.

  __ sd(xmethod, Address(xthread, JavaThread::callee_target_offset()));

  __ jr(t1);
}

// ---------------------------------------------------------------

void SharedRuntime::generate_i2c2i_adapters(MacroAssembler *masm,
                                            int total_args_passed,
                                            int comp_args_on_stack,
                                            const BasicType *sig_bt,
                                            const VMRegPair *regs,
                                            AdapterHandlerEntry* handler) {
  address i2c_entry = __ pc();
  gen_i2c_adapter(masm, total_args_passed, comp_args_on_stack, sig_bt, regs);

  address c2i_unverified_entry = __ pc();
  Label skip_fixup;

  const Register receiver = j_rarg0;
  const Register data = t0;

  // -------------------------------------------------------------------------
  // Generate a C2I adapter.  On entry we know xmethod holds the Method* during calls
  // to the interpreter.  The args start out packed in the compiled layout.  They
  // need to be unpacked into the interpreter layout.  This will almost always
  // require some stack space.  We grow the current (compiled) stack, then repack
  // the args.  We  finally end in a jump to the generic interpreter entry point.
  // On exit from the interpreter, the interpreter will restore our SP (lest the
  // compiled code, which relies solely on SP and not FP, get sick).

  {
    __ block_comment("c2i_unverified_entry {");

    __ ic_check();
    __ ld(xmethod, Address(data, CompiledICData::speculated_method_offset()));

    __ ld(t0, Address(xmethod, in_bytes(Method::code_offset())));
    __ beqz(t0, skip_fixup);
    __ far_jump(RuntimeAddress(SharedRuntime::get_ic_miss_stub()));
    __ block_comment("} c2i_unverified_entry");
  }

  address c2i_entry = __ pc();

  // Class initialization barrier for static methods
  address c2i_no_clinit_check_entry = nullptr;
  if (VM_Version::supports_fast_class_init_checks()) {
    Label L_skip_barrier;

    { // Bypass the barrier for non-static methods
      __ load_unsigned_short(t0, Address(xmethod, Method::access_flags_offset()));
      __ test_bit(t1, t0, exact_log2(JVM_ACC_STATIC));
      __ beqz(t1, L_skip_barrier); // non-static
    }

    __ load_method_holder(t1, xmethod);
    __ clinit_barrier(t1, t0, &L_skip_barrier);
    __ far_jump(RuntimeAddress(SharedRuntime::get_handle_wrong_method_stub()));

    __ bind(L_skip_barrier);
    c2i_no_clinit_check_entry = __ pc();
  }

  BarrierSetAssembler* bs = BarrierSet::barrier_set()->barrier_set_assembler();
  bs->c2i_entry_barrier(masm);

  gen_c2i_adapter(masm, total_args_passed, comp_args_on_stack, sig_bt, regs, skip_fixup);

  handler->set_entry_points(i2c_entry, c2i_entry, c2i_unverified_entry, c2i_no_clinit_check_entry);
  return;
}

int SharedRuntime::vector_calling_convention(VMRegPair *regs,
                                             uint num_bits,
                                             uint total_args_passed) {
  assert(total_args_passed <= Argument::n_vector_register_parameters_c, "unsupported");
  assert(num_bits >= 64 && num_bits <= 2048 && is_power_of_2(num_bits), "unsupported");

  // check more info at https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/master/riscv-cc.adoc
  static const VectorRegister VEC_ArgReg[Argument::n_vector_register_parameters_c] = {
    v8, v9, v10, v11, v12, v13, v14, v15,
    v16, v17, v18, v19, v20, v21, v22, v23
  };

  const int next_reg_val = 3;
  for (uint i = 0; i < total_args_passed; i++) {
    VMReg vmreg = VEC_ArgReg[i]->as_VMReg();
    regs[i].set_pair(vmreg->next(next_reg_val), vmreg);
  }
  return 0;
}

int SharedRuntime::c_calling_convention(const BasicType *sig_bt,
                                         VMRegPair *regs,
                                         int total_args_passed) {

  // We return the amount of VMRegImpl stack slots we need to reserve for all
  // the arguments NOT counting out_preserve_stack_slots.

  static const Register INT_ArgReg[Argument::n_int_register_parameters_c] = {
    c_rarg0, c_rarg1, c_rarg2, c_rarg3,
    c_rarg4, c_rarg5,  c_rarg6,  c_rarg7
  };
  static const FloatRegister FP_ArgReg[Argument::n_float_register_parameters_c] = {
    c_farg0, c_farg1, c_farg2, c_farg3,
    c_farg4, c_farg5, c_farg6, c_farg7
  };

  uint int_args = 0;
  uint fp_args = 0;
  uint stk_args = 0; // inc by 2 each time

  for (int i = 0; i < total_args_passed; i++) {
    switch (sig_bt[i]) {
      case T_BOOLEAN:  // fall through
      case T_CHAR:     // fall through
      case T_BYTE:     // fall through
      case T_SHORT:    // fall through
      case T_INT:
        if (int_args < Argument::n_int_register_parameters_c) {
          regs[i].set1(INT_ArgReg[int_args++]->as_VMReg());
        } else {
          regs[i].set1(VMRegImpl::stack2reg(stk_args));
          stk_args += 2;
        }
        break;
      case T_LONG:      // fall through
        assert((i + 1) < total_args_passed && sig_bt[i + 1] == T_VOID, "expecting half");
      case T_OBJECT:    // fall through
      case T_ARRAY:     // fall through
      case T_ADDRESS:   // fall through
      case T_METADATA:
        if (int_args < Argument::n_int_register_parameters_c) {
          regs[i].set2(INT_ArgReg[int_args++]->as_VMReg());
        } else {
          regs[i].set2(VMRegImpl::stack2reg(stk_args));
          stk_args += 2;
        }
        break;
      case T_FLOAT:
        if (fp_args < Argument::n_float_register_parameters_c) {
          regs[i].set1(FP_ArgReg[fp_args++]->as_VMReg());
        } else if (int_args < Argument::n_int_register_parameters_c) {
          regs[i].set1(INT_ArgReg[int_args++]->as_VMReg());
        } else {
          regs[i].set1(VMRegImpl::stack2reg(stk_args));
          stk_args += 2;
        }
        break;
      case T_DOUBLE:
        assert((i + 1) < total_args_passed && sig_bt[i + 1] == T_VOID, "expecting half");
        if (fp_args < Argument::n_float_register_parameters_c) {
          regs[i].set2(FP_ArgReg[fp_args++]->as_VMReg());
        } else if (int_args < Argument::n_int_register_parameters_c) {
          regs[i].set2(INT_ArgReg[int_args++]->as_VMReg());
        } else {
          regs[i].set2(VMRegImpl::stack2reg(stk_args));
          stk_args += 2;
        }
        break;
      case T_VOID: // Halves of longs and doubles
        assert(i != 0 && (sig_bt[i - 1] == T_LONG || sig_bt[i - 1] == T_DOUBLE), "expecting half");
        regs[i].set_bad();
        break;
      default:
        ShouldNotReachHere();
    }
  }

  return stk_args;
}

void SharedRuntime::save_native_result(MacroAssembler *masm, BasicType ret_type, int frame_slots) {
  // We always ignore the frame_slots arg and just use the space just below frame pointer
  // which by this time is free to use
  switch (ret_type) {
    case T_FLOAT:
      __ fsw(f10, Address(fp, -3 * wordSize));
      break;
    case T_DOUBLE:
      __ fsd(f10, Address(fp, -3 * wordSize));
      break;
    case T_VOID:  break;
    default: {
      __ sd(x10, Address(fp, -3 * wordSize));
    }
  }
}

void SharedRuntime::restore_native_result(MacroAssembler *masm, BasicType ret_type, int frame_slots) {
  // We always ignore the frame_slots arg and just use the space just below frame pointer
  // which by this time is free to use
  switch (ret_type) {
    case T_FLOAT:
      __ flw(f10, Address(fp, -3 * wordSize));
      break;
    case T_DOUBLE:
      __ fld(f10, Address(fp, -3 * wordSize));
      break;
    case T_VOID:  break;
    default: {
      __ ld(x10, Address(fp, -3 * wordSize));
    }
  }
}

static void save_args(MacroAssembler *masm, int arg_count, int first_arg, VMRegPair *args) {
  RegSet x;
  for ( int i = first_arg ; i < arg_count ; i++ ) {
    if (args[i].first()->is_Register()) {
      x = x + args[i].first()->as_Register();
    } else if (args[i].first()->is_FloatRegister()) {
      __ subi(sp, sp, 2 * wordSize);
      __ fsd(args[i].first()->as_FloatRegister(), Address(sp, 0));
    }
  }
  __ push_reg(x, sp);
}

static void restore_args(MacroAssembler *masm, int arg_count, int first_arg, VMRegPair *args) {
  RegSet x;
  for ( int i = first_arg ; i < arg_count ; i++ ) {
    if (args[i].first()->is_Register()) {
      x = x + args[i].first()->as_Register();
    } else {
      ;
    }
  }
  __ pop_reg(x, sp);
  for ( int i = arg_count - 1 ; i >= first_arg ; i-- ) {
    if (args[i].first()->is_Register()) {
      ;
    } else if (args[i].first()->is_FloatRegister()) {
      __ fld(args[i].first()->as_FloatRegister(), Address(sp, 0));
      __ addi(sp, sp, 2 * wordSize);
    }
  }
}

static void verify_oop_args(MacroAssembler* masm,
                            const methodHandle& method,
                            const BasicType* sig_bt,
                            const VMRegPair* regs) {
  const Register temp_reg = x9;  // not part of any compiled calling seq
  if (VerifyOops) {
    for (int i = 0; i < method->size_of_parameters(); i++) {
      if (sig_bt[i] == T_OBJECT ||
          sig_bt[i] == T_ARRAY) {
        VMReg r = regs[i].first();
        assert(r->is_valid(), "bad oop arg");
        if (r->is_stack()) {
          __ ld(temp_reg, Address(sp, r->reg2stack() * VMRegImpl::stack_slot_size));
          __ verify_oop(temp_reg);
        } else {
          __ verify_oop(r->as_Register());
        }
      }
    }
  }
}

// on exit, sp points to the ContinuationEntry
static OopMap* continuation_enter_setup(MacroAssembler* masm, int& stack_slots) {
  assert(ContinuationEntry::size() % VMRegImpl::stack_slot_size == 0, "");
  assert(in_bytes(ContinuationEntry::cont_offset())  % VMRegImpl::stack_slot_size == 0, "");
  assert(in_bytes(ContinuationEntry::chunk_offset()) % VMRegImpl::stack_slot_size == 0, "");

  stack_slots += (int)ContinuationEntry::size() / wordSize;
  __ sub(sp, sp, (int)ContinuationEntry::size()); // place Continuation metadata

  OopMap* map = new OopMap(((int)ContinuationEntry::size() + wordSize) / VMRegImpl::stack_slot_size, 0 /* arg_slots*/);

  __ ld(t0, Address(xthread, JavaThread::cont_entry_offset()));
  __ sd(t0, Address(sp, ContinuationEntry::parent_offset()));
  __ sd(sp, Address(xthread, JavaThread::cont_entry_offset()));

  return map;
}

// on entry c_rarg1 points to the continuation
//          sp points to ContinuationEntry
//          c_rarg3 -- isVirtualThread
static void fill_continuation_entry(MacroAssembler* masm) {
#ifdef ASSERT
  __ mv(t0, ContinuationEntry::cookie_value());
  __ sw(t0, Address(sp, ContinuationEntry::cookie_offset()));
#endif

  __ sd(c_rarg1, Address(sp, ContinuationEntry::cont_offset()));
  __ sw(c_rarg3, Address(sp, ContinuationEntry::flags_offset()));
  __ sd(zr,      Address(sp, ContinuationEntry::chunk_offset()));
  __ sw(zr,      Address(sp, ContinuationEntry::argsize_offset()));
  __ sw(zr,      Address(sp, ContinuationEntry::pin_count_offset()));

  __ ld(t0, Address(xthread, JavaThread::cont_fastpath_offset()));
  __ sd(t0, Address(sp, ContinuationEntry::parent_cont_fastpath_offset()));
  __ ld(t0, Address(xthread, JavaThread::held_monitor_count_offset()));
  __ sd(t0, Address(sp, ContinuationEntry::parent_held_monitor_count_offset()));

  __ sd(zr, Address(xthread, JavaThread::cont_fastpath_offset()));
  __ sd(zr, Address(xthread, JavaThread::held_monitor_count_offset()));
}

// on entry, sp points to the ContinuationEntry
// on exit, fp points to the spilled fp + 2 * wordSize in the entry frame
static void continuation_enter_cleanup(MacroAssembler* masm) {
#ifndef PRODUCT
  Label OK;
  __ ld(t0, Address(xthread, JavaThread::cont_entry_offset()));
  __ beq(sp, t0, OK);
  __ stop("incorrect sp");
  __ bind(OK);
#endif

  __ ld(t0, Address(sp, ContinuationEntry::parent_cont_fastpath_offset()));
  __ sd(t0, Address(xthread, JavaThread::cont_fastpath_offset()));

  if (CheckJNICalls) {
    // Check if this is a virtual thread continuation
    Label L_skip_vthread_code;
    __ lwu(t0, Address(sp, ContinuationEntry::flags_offset()));
    __ beqz(t0, L_skip_vthread_code);

    // If the held monitor count is > 0 and this vthread is terminating then
    // it failed to release a JNI monitor. So we issue the same log message
    // that JavaThread::exit does.
    __ ld(t0, Address(xthread, JavaThread::jni_monitor_count_offset()));
    __ beqz(t0, L_skip_vthread_code);

    // Save return value potentially containing the exception oop in callee-saved x9
    __ mv(x9, x10);
    __ call_VM_leaf(CAST_FROM_FN_PTR(address, SharedRuntime::log_jni_monitor_still_held));
    // Restore potential return value
    __ mv(x10, x9);

    // For vthreads we have to explicitly zero the JNI monitor count of the carrier
    // on termination. The held count is implicitly zeroed below when we restore from
    // the parent held count (which has to be zero).
    __ sd(zr, Address(xthread, JavaThread::jni_monitor_count_offset()));

    __ bind(L_skip_vthread_code);
  }
#ifdef ASSERT
  else {
    // Check if this is a virtual thread continuation
    Label L_skip_vthread_code;
    __ lwu(t0, Address(sp, ContinuationEntry::flags_offset()));
    __ beqz(t0, L_skip_vthread_code);

    // See comment just above. If not checking JNI calls the JNI count is only
    // needed for assertion checking.
    __ sd(zr, Address(xthread, JavaThread::jni_monitor_count_offset()));

    __ bind(L_skip_vthread_code);
  }
#endif

  __ ld(t0, Address(sp, ContinuationEntry::parent_held_monitor_count_offset()));
  __ sd(t0, Address(xthread, JavaThread::held_monitor_count_offset()));

  __ ld(t0, Address(sp, ContinuationEntry::parent_offset()));
  __ sd(t0, Address(xthread, JavaThread::cont_entry_offset()));
  __ add(fp, sp, (int)ContinuationEntry::size() + 2 * wordSize /* 2 extra words to match up with leave() */);
}

// enterSpecial(Continuation c, boolean isContinue, boolean isVirtualThread)
// On entry: c_rarg1 -- the continuation object
//           c_rarg2 -- isContinue
//           c_rarg3 -- isVirtualThread
static void gen_continuation_enter(MacroAssembler* masm,
                                   const methodHandle& method,
                                   const BasicType* sig_bt,
                                   const VMRegPair* regs,
                                   int& exception_offset,
                                   OopMapSet*oop_maps,
                                   int& frame_complete,
                                   int& stack_slots,
                                   int& interpreted_entry_offset,
                                   int& compiled_entry_offset) {
  // verify_oop_args(masm, method, sig_bt, regs);
  Address resolve(SharedRuntime::get_resolve_static_call_stub(), relocInfo::static_call_type);

  address start = __ pc();

  Label call_thaw, exit;

  // i2i entry used at interp_only_mode only
  interpreted_entry_offset = __ pc() - start;
  {
#ifdef ASSERT
    Label is_interp_only;
    __ lw(t0, Address(xthread, JavaThread::interp_only_mode_offset()));
    __ bnez(t0, is_interp_only);
    __ stop("enterSpecial interpreter entry called when not in interp_only_mode");
    __ bind(is_interp_only);
#endif

    // Read interpreter arguments into registers (this is an ad-hoc i2c adapter)
    __ ld(c_rarg1, Address(esp, Interpreter::stackElementSize * 2));
    __ ld(c_rarg2, Address(esp, Interpreter::stackElementSize * 1));
    __ ld(c_rarg3, Address(esp, Interpreter::stackElementSize * 0));
    __ push_cont_fastpath(xthread);

    __ enter();
    stack_slots = 2; // will be adjusted in setup
    OopMap* map = continuation_enter_setup(masm, stack_slots);
    // The frame is complete here, but we only record it for the compiled entry, so the frame would appear unsafe,
    // but that's okay because at the very worst we'll miss an async sample, but we're in interp_only_mode anyway.

    fill_continuation_entry(masm);

    __ bnez(c_rarg2, call_thaw);

    address call_pc;
    {
      Assembler::IncompressibleScope scope(masm);
      // Make sure the call is patchable
      __ align(NativeInstruction::instruction_size);

      call_pc = __ reloc_call(resolve);
      if (call_pc == nullptr) {
        fatal("CodeCache is full at gen_continuation_enter");
      }

      oop_maps->add_gc_map(__ pc() - start, map);
      __ post_call_nop();
    }
    __ j(exit);

    address stub = CompiledDirectCall::emit_to_interp_stub(masm, call_pc);
    if (stub == nullptr) {
      fatal("CodeCache is full at gen_continuation_enter");
    }
  }

  // compiled entry
  __ align(CodeEntryAlignment);
  compiled_entry_offset = __ pc() - start;

  __ enter();
  stack_slots = 2; // will be adjusted in setup
  OopMap* map = continuation_enter_setup(masm, stack_slots);
  frame_complete = __ pc() - start;

  fill_continuation_entry(masm);

  __ bnez(c_rarg2, call_thaw);

  address call_pc;
  {
    Assembler::IncompressibleScope scope(masm);
    // Make sure the call is patchable
    __ align(NativeInstruction::instruction_size);

    call_pc = __ reloc_call(resolve);
    if (call_pc == nullptr) {
      fatal("CodeCache is full at gen_continuation_enter");
    }

    oop_maps->add_gc_map(__ pc() - start, map);
    __ post_call_nop();
  }

  __ j(exit);

  __ bind(call_thaw);

  // Post call nops must be natural aligned due to cmodx rules.
  {
    Assembler::IncompressibleScope scope(masm);
    __ align(NativeInstruction::instruction_size);

    ContinuationEntry::_thaw_call_pc_offset = __ pc() - start;
    __ rt_call(CAST_FROM_FN_PTR(address, StubRoutines::cont_thaw()));
    oop_maps->add_gc_map(__ pc() - start, map->deep_copy());
    ContinuationEntry::_return_pc_offset = __ pc() - start;
    __ post_call_nop();
  }

  __ bind(exit);
  ContinuationEntry::_cleanup_offset = __ pc() - start;
  continuation_enter_cleanup(masm);
  __ leave();
  __ ret();

  // exception handling
  exception_offset = __ pc() - start;
  {
    __ mv(x9, x10); // save return value contaning the exception oop in callee-saved x9

    continuation_enter_cleanup(masm);

    __ ld(c_rarg1, Address(fp, -1 * wordSize)); // return address
    __ call_VM_leaf(CAST_FROM_FN_PTR(address, SharedRuntime::exception_handler_for_return_address), xthread, c_rarg1);

    // see OptoRuntime::generate_exception_blob: x10 -- exception oop, x13 -- exception pc

    __ mv(x11, x10); // the exception handler
    __ mv(x10, x9); // restore return value contaning the exception oop
    __ verify_oop(x10);

    __ leave();
    __ mv(x13, ra);
    __ jr(x11); // the exception handler
  }

  address stub = CompiledDirectCall::emit_to_interp_stub(masm, call_pc);
  if (stub == nullptr) {
    fatal("CodeCache is full at gen_continuation_enter");
  }
}

static void gen_continuation_yield(MacroAssembler* masm,
                                   const methodHandle& method,
                                   const BasicType* sig_bt,
                                   const VMRegPair* regs,
                                   OopMapSet* oop_maps,
                                   int& frame_complete,
                                   int& stack_slots,
                                   int& compiled_entry_offset) {
  enum layout {
    fp_off,
    fp_off2,
    return_off,
    return_off2,
    framesize // inclusive of return address
  };
  // assert(is_even(framesize/2), "sp not 16-byte aligned");

  stack_slots = framesize / VMRegImpl::slots_per_word;
  assert(stack_slots == 2, "recheck layout");

  address start = __ pc();

  compiled_entry_offset = __ pc() - start;
  __ enter();

  __ mv(c_rarg1, sp);

  // Post call nops must be natural aligned due to cmodx rules.
  __ align(NativeInstruction::instruction_size);

  frame_complete = __ pc() - start;
  address the_pc = __ pc();

  {
    Assembler::IncompressibleScope scope(masm);
    __ post_call_nop(); // this must be exactly after the pc value that is pushed into the frame info, we use this nop for fast CodeBlob lookup
  }

  __ mv(c_rarg0, xthread);
  __ set_last_Java_frame(sp, fp, the_pc, t0);
  __ call_VM_leaf(Continuation::freeze_entry(), 2);
  __ reset_last_Java_frame(true);

  Label pinned;

  __ bnez(x10, pinned);

  // We've succeeded, set sp to the ContinuationEntry
  __ ld(sp, Address(xthread, JavaThread::cont_entry_offset()));
  continuation_enter_cleanup(masm);

  __ bind(pinned); // pinned -- return to caller

  // handle pending exception thrown by freeze
  __ ld(t0, Address(xthread, in_bytes(Thread::pending_exception_offset())));
  Label ok;
  __ beqz(t0, ok);
  __ leave();
  __ j(RuntimeAddress(StubRoutines::forward_exception_entry()));
  __ bind(ok);

  __ leave();
  __ ret();

  OopMap* map = new OopMap(framesize, 1);
  oop_maps->add_gc_map(the_pc - start, map);
}

void SharedRuntime::continuation_enter_cleanup(MacroAssembler* masm) {
  ::continuation_enter_cleanup(masm);
}

static void gen_special_dispatch(MacroAssembler* masm,
                                 const methodHandle& method,
                                 const BasicType* sig_bt,
                                 const VMRegPair* regs) {
  verify_oop_args(masm, method, sig_bt, regs);
  vmIntrinsics::ID iid = method->intrinsic_id();

  // Now write the args into the outgoing interpreter space
  bool     has_receiver   = false;
  Register receiver_reg   = noreg;
  int      member_arg_pos = -1;
  Register member_reg     = noreg;
  int      ref_kind       = MethodHandles::signature_polymorphic_intrinsic_ref_kind(iid);
  if (ref_kind != 0) {
    member_arg_pos = method->size_of_parameters() - 1;  // trailing MemberName argument
    member_reg = x9;  // known to be free at this point
    has_receiver = MethodHandles::ref_kind_has_receiver(ref_kind);
  } else if (iid == vmIntrinsics::_invokeBasic) {
    has_receiver = true;
  } else if (iid == vmIntrinsics::_linkToNative) {
    member_arg_pos = method->size_of_parameters() - 1;  // trailing NativeEntryPoint argument
    member_reg = x9;  // known to be free at this point
  } else {
    fatal("unexpected intrinsic id %d", vmIntrinsics::as_int(iid));
  }

  if (member_reg != noreg) {
    // Load the member_arg into register, if necessary.
    SharedRuntime::check_member_name_argument_is_last_argument(method, sig_bt, regs);
    VMReg r = regs[member_arg_pos].first();
    if (r->is_stack()) {
      __ ld(member_reg, Address(sp, r->reg2stack() * VMRegImpl::stack_slot_size));
    } else {
      // no data motion is needed
      member_reg = r->as_Register();
    }
  }

  if (has_receiver) {
    // Make sure the receiver is loaded into a register.
    assert(method->size_of_parameters() > 0, "oob");
    assert(sig_bt[0] == T_OBJECT, "receiver argument must be an object");
    VMReg r = regs[0].first();
    assert(r->is_valid(), "bad receiver arg");
    if (r->is_stack()) {
      // Porting note:  This assumes that compiled calling conventions always
      // pass the receiver oop in a register.  If this is not true on some
      // platform, pick a temp and load the receiver from stack.
      fatal("receiver always in a register");
      receiver_reg = x12;  // known to be free at this point
      __ ld(receiver_reg, Address(sp, r->reg2stack() * VMRegImpl::stack_slot_size));
    } else {
      // no data motion is needed
      receiver_reg = r->as_Register();
    }
  }

  // Figure out which address we are really jumping to:
  MethodHandles::generate_method_handle_dispatch(masm, iid,
                                                 receiver_reg, member_reg, /*for_compiler_entry:*/ true);
}

// ---------------------------------------------------------------------------
// Generate a native wrapper for a given method.  The method takes arguments
// in the Java compiled code convention, marshals them to the native
// convention (handlizes oops, etc), transitions to native, makes the call,
// returns to java state (possibly blocking), unhandlizes any result and
// returns.
//
// Critical native functions are a shorthand for the use of
// GetPrimtiveArrayCritical and disallow the use of any other JNI
// functions.  The wrapper is expected to unpack the arguments before
// passing them to the callee and perform checks before and after the
// native call to ensure that they GCLocker
// lock_critical/unlock_critical semantics are followed.  Some other
// parts of JNI setup are skipped like the tear down of the JNI handle
// block and the check for pending exceptions it's impossible for them
// to be thrown.
//
// They are roughly structured like this:
//    if (GCLocker::needs_gc()) SharedRuntime::block_for_jni_critical()
//    tranistion to thread_in_native
//    unpack array arguments and call native entry point
//    check for safepoint in progress
//    check if any thread suspend flags are set
//      call into JVM and possible unlock the JNI critical
//      if a GC was suppressed while in the critical native.
//    transition back to thread_in_Java
//    return to caller
//
nmethod* SharedRuntime::generate_native_wrapper(MacroAssembler* masm,
                                                const methodHandle& method,
                                                int compile_id,
                                                BasicType* in_sig_bt,
                                                VMRegPair* in_regs,
                                                BasicType ret_type) {
  if (method->is_continuation_native_intrinsic()) {
    int exception_offset = -1;
    OopMapSet* oop_maps = new OopMapSet();
    int frame_complete = -1;
    int stack_slots = -1;
    int interpreted_entry_offset = -1;
    int vep_offset = -1;
    if (method->is_continuation_enter_intrinsic()) {
      gen_continuation_enter(masm,
                             method,
                             in_sig_bt,
                             in_regs,
                             exception_offset,
                             oop_maps,
                             frame_complete,
                             stack_slots,
                             interpreted_entry_offset,
                             vep_offset);
    } else if (method->is_continuation_yield_intrinsic()) {
      gen_continuation_yield(masm,
                             method,
                             in_sig_bt,
                             in_regs,
                             oop_maps,
                             frame_complete,
                             stack_slots,
                             vep_offset);
    } else {
      guarantee(false, "Unknown Continuation native intrinsic");
    }

#ifdef ASSERT
    if (method->is_continuation_enter_intrinsic()) {
      assert(interpreted_entry_offset != -1, "Must be set");
      assert(exception_offset != -1,         "Must be set");
    } else {
      assert(interpreted_entry_offset == -1, "Must be unset");
      assert(exception_offset == -1,         "Must be unset");
    }
    assert(frame_complete != -1,    "Must be set");
    assert(stack_slots != -1,       "Must be set");
    assert(vep_offset != -1,        "Must be set");
#endif

    __ flush();
    nmethod* nm = nmethod::new_native_nmethod(method,
                                              compile_id,
                                              masm->code(),
                                              vep_offset,
                                              frame_complete,
                                              stack_slots,
                                              in_ByteSize(-1),
                                              in_ByteSize(-1),
                                              oop_maps,
                                              exception_offset);
    if (nm == nullptr) return nm;
    if (method->is_continuation_enter_intrinsic()) {
      ContinuationEntry::set_enter_code(nm, interpreted_entry_offset);
    } else if (method->is_continuation_yield_intrinsic()) {
      _cont_doYield_stub = nm;
    } else {
      guarantee(false, "Unknown Continuation native intrinsic");
    }
    return nm;
  }

  if (method->is_method_handle_intrinsic()) {
    vmIntrinsics::ID iid = method->intrinsic_id();
    intptr_t start = (intptr_t)__ pc();
    int vep_offset = ((intptr_t)__ pc()) - start;

    // First instruction must be a nop as it may need to be patched on deoptimisation
    {
      Assembler::IncompressibleScope scope(masm); // keep the nop as 4 bytes for patching.
      MacroAssembler::assert_alignment(__ pc());
      __ nop();  // 4 bytes
    }
    gen_special_dispatch(masm,
                         method,
                         in_sig_bt,
                         in_regs);
    int frame_complete = ((intptr_t)__ pc()) - start;  // not complete, period
    __ flush();
    int stack_slots = SharedRuntime::out_preserve_stack_slots();  // no out slots at all, actually
    return nmethod::new_native_nmethod(method,
                                       compile_id,
                                       masm->code(),
                                       vep_offset,
                                       frame_complete,
                                       stack_slots / VMRegImpl::slots_per_word,
                                       in_ByteSize(-1),
                                       in_ByteSize(-1),
                                       (OopMapSet*)nullptr);
  }
  address native_func = method->native_function();
  assert(native_func != nullptr, "must have function");

  // An OopMap for lock (and class if static)
  OopMapSet *oop_maps = new OopMapSet();
  assert_cond(oop_maps != nullptr);
  intptr_t start = (intptr_t)__ pc();

  // We have received a description of where all the java arg are located
  // on entry to the wrapper. We need to convert these args to where
  // the jni function will expect them. To figure out where they go
  // we convert the java signature to a C signature by inserting
  // the hidden arguments as arg[0] and possibly arg[1] (static method)

  const int total_in_args = method->size_of_parameters();
  int total_c_args = total_in_args + (method->is_static() ? 2 : 1);

  BasicType* out_sig_bt = NEW_RESOURCE_ARRAY(BasicType, total_c_args);
  VMRegPair* out_regs   = NEW_RESOURCE_ARRAY(VMRegPair, total_c_args);

  int argc = 0;
  out_sig_bt[argc++] = T_ADDRESS;
  if (method->is_static()) {
    out_sig_bt[argc++] = T_OBJECT;
  }

  for (int i = 0; i < total_in_args ; i++) {
    out_sig_bt[argc++] = in_sig_bt[i];
  }

  // Now figure out where the args must be stored and how much stack space
  // they require.
  int out_arg_slots = c_calling_convention(out_sig_bt, out_regs, total_c_args);

  // Compute framesize for the wrapper.  We need to handlize all oops in
  // incoming registers

  // Calculate the total number of stack slots we will need.

  // First count the abi requirement plus all of the outgoing args
  int stack_slots = SharedRuntime::out_preserve_stack_slots() + out_arg_slots;

  // Now the space for the inbound oop handle area
  int total_save_slots = 8 * VMRegImpl::slots_per_word;  // 8 arguments passed in registers

  int oop_handle_offset = stack_slots;
  stack_slots += total_save_slots;

  // Now any space we need for handlizing a klass if static method

  int klass_slot_offset = 0;
  int klass_offset = -1;
  int lock_slot_offset = 0;
  bool is_static = false;

  if (method->is_static()) {
    klass_slot_offset = stack_slots;
    stack_slots += VMRegImpl::slots_per_word;
    klass_offset = klass_slot_offset * VMRegImpl::stack_slot_size;
    is_static = true;
  }

  // Plus a lock if needed

  if (method->is_synchronized()) {
    lock_slot_offset = stack_slots;
    stack_slots += VMRegImpl::slots_per_word;
  }

  // Now a place (+2) to save return values or temp during shuffling
  // + 4 for return address (which we own) and saved fp
  stack_slots += 6;

  // Ok The space we have allocated will look like:
  //
  //
  // FP-> |                     |
  //      | 2 slots (ra)        |
  //      | 2 slots (fp)        |
  //      |---------------------|
  //      | 2 slots for moves   |
  //      |---------------------|
  //      | lock box (if sync)  |
  //      |---------------------| <- lock_slot_offset
  //      | klass (if static)   |
  //      |---------------------| <- klass_slot_offset
  //      | oopHandle area      |
  //      |---------------------| <- oop_handle_offset (8 java arg registers)
  //      | outbound memory     |
  //      | based arguments     |
  //      |                     |
  //      |---------------------|
  //      |                     |
  // SP-> | out_preserved_slots |
  //
  //


  // Now compute actual number of stack words we need rounding to make
  // stack properly aligned.
  stack_slots = align_up(stack_slots, StackAlignmentInSlots);

  int stack_size = stack_slots * VMRegImpl::stack_slot_size;

  // First thing make an ic check to see if we should even be here

  // We are free to use all registers as temps without saving them and
  // restoring them except fp. fp is the only callee save register
  // as far as the interpreter and the compiler(s) are concerned.

  const Register receiver = j_rarg0;

  __ verify_oop(receiver);
  assert_different_registers(receiver, t0, t1);

  __ ic_check();

  int vep_offset = ((intptr_t)__ pc()) - start;

  // If we have to make this method not-entrant we'll overwrite its
  // first instruction with a jump.
  {
    Assembler::IncompressibleScope scope(masm); // keep the nop as 4 bytes for patching.
    MacroAssembler::assert_alignment(__ pc());
    __ nop();  // 4 bytes
  }

  if (VM_Version::supports_fast_class_init_checks() && method->needs_clinit_barrier()) {
    Label L_skip_barrier;
    __ mov_metadata(t1, method->method_holder()); // InstanceKlass*
    __ clinit_barrier(t1, t0, &L_skip_barrier);
    __ far_jump(RuntimeAddress(SharedRuntime::get_handle_wrong_method_stub()));

    __ bind(L_skip_barrier);
  }

  // Generate stack overflow check
  __ bang_stack_with_offset(checked_cast<int>(StackOverflow::stack_shadow_zone_size()));

  // Generate a new frame for the wrapper.
  __ enter();
  // -2 because return address is already present and so is saved fp
  __ sub(sp, sp, stack_size - 2 * wordSize);

  BarrierSetAssembler* bs = BarrierSet::barrier_set()->barrier_set_assembler();
  assert_cond(bs != nullptr);
  bs->nmethod_entry_barrier(masm, nullptr /* slow_path */, nullptr /* continuation */, nullptr /* guard */);

  // Frame is now completed as far as size and linkage.
  int frame_complete = ((intptr_t)__ pc()) - start;

  // We use x18 as the oop handle for the receiver/klass
  // It is callee save so it survives the call to native

  const Register oop_handle_reg = x18;

  //
  // We immediately shuffle the arguments so that any vm call we have to
  // make from here on out (sync slow path, jvmti, etc.) we will have
  // captured the oops from our caller and have a valid oopMap for
  // them.

  // -----------------
  // The Grand Shuffle

  // The Java calling convention is either equal (linux) or denser (win64) than the
  // c calling convention. However the because of the jni_env argument the c calling
  // convention always has at least one more (and two for static) arguments than Java.
  // Therefore if we move the args from java -> c backwards then we will never have
  // a register->register conflict and we don't have to build a dependency graph
  // and figure out how to break any cycles.
  //

  // Record esp-based slot for receiver on stack for non-static methods
  int receiver_offset = -1;

  // This is a trick. We double the stack slots so we can claim
  // the oops in the caller's frame. Since we are sure to have
  // more args than the caller doubling is enough to make
  // sure we can capture all the incoming oop args from the
  // caller.
  //
  OopMap* map = new OopMap(stack_slots * 2, 0 /* arg_slots*/);
  assert_cond(map != nullptr);

  int float_args = 0;
  int int_args = 0;

#ifdef ASSERT
  bool reg_destroyed[Register::number_of_registers];
  bool freg_destroyed[FloatRegister::number_of_registers];
  for ( int r = 0 ; r < Register::number_of_registers ; r++ ) {
    reg_destroyed[r] = false;
  }
  for ( int f = 0 ; f < FloatRegister::number_of_registers ; f++ ) {
    freg_destroyed[f] = false;
  }

#endif /* ASSERT */

  // For JNI natives the incoming and outgoing registers are offset upwards.
  GrowableArray<int> arg_order(2 * total_in_args);

  for (int i = total_in_args - 1, c_arg = total_c_args - 1; i >= 0; i--, c_arg--) {
    arg_order.push(i);
    arg_order.push(c_arg);
  }

  for (int ai = 0; ai < arg_order.length(); ai += 2) {
    int i = arg_order.at(ai);
    int c_arg = arg_order.at(ai + 1);
    __ block_comment(err_msg("mv %d -> %d", i, c_arg));
    assert(c_arg != -1 && i != -1, "wrong order");
#ifdef ASSERT
    if (in_regs[i].first()->is_Register()) {
      assert(!reg_destroyed[in_regs[i].first()->as_Register()->encoding()], "destroyed reg!");
    } else if (in_regs[i].first()->is_FloatRegister()) {
      assert(!freg_destroyed[in_regs[i].first()->as_FloatRegister()->encoding()], "destroyed reg!");
    }
    if (out_regs[c_arg].first()->is_Register()) {
      reg_destroyed[out_regs[c_arg].first()->as_Register()->encoding()] = true;
    } else if (out_regs[c_arg].first()->is_FloatRegister()) {
      freg_destroyed[out_regs[c_arg].first()->as_FloatRegister()->encoding()] = true;
    }
#endif /* ASSERT */
    switch (in_sig_bt[i]) {
      case T_ARRAY:
      case T_OBJECT:
        __ object_move(map, oop_handle_offset, stack_slots, in_regs[i], out_regs[c_arg],
                       ((i == 0) && (!is_static)),
                       &receiver_offset);
        int_args++;
        break;
      case T_VOID:
        break;

      case T_FLOAT:
        __ float_move(in_regs[i], out_regs[c_arg]);
        float_args++;
        break;

      case T_DOUBLE:
        assert( i + 1 < total_in_args &&
                in_sig_bt[i + 1] == T_VOID &&
                out_sig_bt[c_arg + 1] == T_VOID, "bad arg list");
        __ double_move(in_regs[i], out_regs[c_arg]);
        float_args++;
        break;

      case T_LONG :
        __ long_move(in_regs[i], out_regs[c_arg]);
        int_args++;
        break;

      case T_ADDRESS:
        assert(false, "found T_ADDRESS in java args");
        break;

      default:
        __ move32_64(in_regs[i], out_regs[c_arg]);
        int_args++;
    }
  }

  // point c_arg at the first arg that is already loaded in case we
  // need to spill before we call out
  int c_arg = total_c_args - total_in_args;

  // Pre-load a static method's oop into c_rarg1.
  if (method->is_static()) {

    //  load oop into a register
    __ movoop(c_rarg1,
              JNIHandles::make_local(method->method_holder()->java_mirror()));

    // Now handlize the static class mirror it's known not-null.
    __ sd(c_rarg1, Address(sp, klass_offset));
    map->set_oop(VMRegImpl::stack2reg(klass_slot_offset));

    // Now get the handle
    __ la(c_rarg1, Address(sp, klass_offset));
    // and protect the arg if we must spill
    c_arg--;
  }

  // Change state to native (we save the return address in the thread, since it might not
  // be pushed on the stack when we do a stack traversal). It is enough that the pc()
  // points into the right code segment. It does not have to be the correct return pc.
  // We use the same pc/oopMap repeatedly when we call out.

  Label native_return;
  if (LockingMode != LM_LEGACY && method->is_object_wait0()) {
    // For convenience we use the pc we want to resume to in case of preemption on Object.wait.
    __ set_last_Java_frame(sp, noreg, native_return, t0);
  } else {
    intptr_t the_pc = (intptr_t) __ pc();
    oop_maps->add_gc_map(the_pc - start, map);

    __ set_last_Java_frame(sp, noreg, __ pc(), t0);
  }

  Label dtrace_method_entry, dtrace_method_entry_done;
  if (DTraceMethodProbes) {
    __ j(dtrace_method_entry);
    __ bind(dtrace_method_entry_done);
  }

  // RedefineClasses() tracing support for obsolete method entry
  if (log_is_enabled(Trace, redefine, class, obsolete)) {
    // protect the args we've loaded
    save_args(masm, total_c_args, c_arg, out_regs);
    __ mov_metadata(c_rarg1, method());
    __ call_VM_leaf(
      CAST_FROM_FN_PTR(address, SharedRuntime::rc_trace_method_entry),
      xthread, c_rarg1);
    restore_args(masm, total_c_args, c_arg, out_regs);
  }

  // Lock a synchronized method

  // Register definitions used by locking and unlocking

  const Register swap_reg = x10;
  const Register obj_reg  = x9;  // Will contain the oop
  const Register lock_reg = x30;  // Address of compiler lock object (BasicLock)
  const Register old_hdr  = x30;  // value of old header at unlock time
  const Register lock_tmp = x31;  // Temporary used by lightweight_lock/unlock
  const Register tmp      = ra;

  Label slow_path_lock;
  Label lock_done;

  if (method->is_synchronized()) {
    Label count;

    const int mark_word_offset = BasicLock::displaced_header_offset_in_bytes();

    // Get the handle (the 2nd argument)
    __ mv(oop_handle_reg, c_rarg1);

    // Get address of the box

    __ la(lock_reg, Address(sp, lock_slot_offset * VMRegImpl::stack_slot_size));

    // Load the oop from the handle
    __ ld(obj_reg, Address(oop_handle_reg, 0));

    if (LockingMode == LM_MONITOR) {
      __ j(slow_path_lock);
    } else if (LockingMode == LM_LEGACY) {
      // Load (object->mark() | 1) into swap_reg % x10
      __ ld(t0, Address(obj_reg, oopDesc::mark_offset_in_bytes()));
      __ ori(swap_reg, t0, 1);

      // Save (object->mark() | 1) into BasicLock's displaced header
      __ sd(swap_reg, Address(lock_reg, mark_word_offset));

      // src -> dest if dest == x10 else x10 <- dest
      __ cmpxchg_obj_header(x10, lock_reg, obj_reg, lock_tmp, count, /*fallthrough*/nullptr);

      // Test if the oopMark is an obvious stack pointer, i.e.,
      //  1) (mark & 3) == 0, and
      //  2) sp <= mark < mark + os::pagesize()
      // These 3 tests can be done by evaluating the following
      // expression: ((mark - sp) & (3 - os::vm_page_size())),
      // assuming both stack pointer and pagesize have their
      // least significant 2 bits clear.
      // NOTE: the oopMark is in swap_reg % 10 as the result of cmpxchg

      __ sub(swap_reg, swap_reg, sp);
      __ mv(t0, 3 - (int)os::vm_page_size());
      __ andr(swap_reg, swap_reg, t0);

      // Save the test result, for recursive case, the result is zero
      __ sd(swap_reg, Address(lock_reg, mark_word_offset));
      __ bnez(swap_reg, slow_path_lock);

      __ bind(count);
      __ inc_held_monitor_count(t0);
    } else {
      assert(LockingMode == LM_LIGHTWEIGHT, "must be");
      __ lightweight_lock(lock_reg, obj_reg, swap_reg, tmp, lock_tmp, slow_path_lock);
    }

    // Slow path will re-enter here
    __ bind(lock_done);
  }


  // Finally just about ready to make the JNI call

  // get JNIEnv* which is first argument to native
  __ la(c_rarg0, Address(xthread, in_bytes(JavaThread::jni_environment_offset())));

  // Now set thread in native
  __ la(t1, Address(xthread, JavaThread::thread_state_offset()));
  __ mv(t0, _thread_in_native);
  __ membar(MacroAssembler::LoadStore | MacroAssembler::StoreStore);
  __ sw(t0, Address(t1));

  // Clobbers t1
  __ rt_call(native_func);

  // Verify or restore cpu control state after JNI call
  __ restore_cpu_control_state_after_jni(t0);

  // Unpack native results.
  if (ret_type != T_OBJECT && ret_type != T_ARRAY) {
    __ cast_primitive_type(ret_type, x10);
  }

  Label safepoint_in_progress, safepoint_in_progress_done;

  // Switch thread to "native transition" state before reading the synchronization state.
  // This additional state is necessary because reading and testing the synchronization
  // state is not atomic w.r.t. GC, as this scenario demonstrates:
  //     Java thread A, in _thread_in_native state, loads _not_synchronized and is preempted.
  //     VM thread changes sync state to synchronizing and suspends threads for GC.
  //     Thread A is resumed to finish this native method, but doesn't block here since it
  //     didn't see any synchronization is progress, and escapes.
  __ mv(t0, _thread_in_native_trans);

  __ sw(t0, Address(xthread, JavaThread::thread_state_offset()));

  // Force this write out before the read below
  if (!UseSystemMemoryBarrier) {
    __ membar(MacroAssembler::AnyAny);
  }

  // check for safepoint operation in progress and/or pending suspend requests
  {
    __ safepoint_poll(safepoint_in_progress, true /* at_return */, false /* in_nmethod */);
    __ lwu(t0, Address(xthread, JavaThread::suspend_flags_offset()));
    __ bnez(t0, safepoint_in_progress);
    __ bind(safepoint_in_progress_done);
  }

  // change thread state
  __ la(t1, Address(xthread, JavaThread::thread_state_offset()));
  __ mv(t0, _thread_in_Java);
  __ membar(MacroAssembler::LoadStore | MacroAssembler::StoreStore);
  __ sw(t0, Address(t1));

  if (LockingMode != LM_LEGACY && method->is_object_wait0()) {
    // Check preemption for Object.wait()
    __ ld(t1, Address(xthread, JavaThread::preempt_alternate_return_offset()));
    __ beqz(t1, native_return);
    __ sd(zr, Address(xthread, JavaThread::preempt_alternate_return_offset()));
    __ jr(t1);
    __ bind(native_return);

    intptr_t the_pc = (intptr_t) __ pc();
    oop_maps->add_gc_map(the_pc - start, map);
  }

  Label reguard;
  Label reguard_done;
  __ lbu(t0, Address(xthread, JavaThread::stack_guard_state_offset()));
  __ mv(t1, StackOverflow::stack_guard_yellow_reserved_disabled);
  __ beq(t0, t1, reguard);
  __ bind(reguard_done);

  // native result if any is live

  // Unlock
  Label unlock_done;
  Label slow_path_unlock;
  if (method->is_synchronized()) {

    // Get locked oop from the handle we passed to jni
    __ ld(obj_reg, Address(oop_handle_reg, 0));

    Label done, not_recursive;

    if (LockingMode == LM_LEGACY) {
      // Simple recursive lock?
      __ ld(t0, Address(sp, lock_slot_offset * VMRegImpl::stack_slot_size));
      __ bnez(t0, not_recursive);
      __ dec_held_monitor_count(t0);
      __ j(done);
    }

    __ bind(not_recursive);

    // Must save x10 if if it is live now because cmpxchg must use it
    if (ret_type != T_FLOAT && ret_type != T_DOUBLE && ret_type != T_VOID) {
      save_native_result(masm, ret_type, stack_slots);
    }

    if (LockingMode == LM_MONITOR) {
      __ j(slow_path_unlock);
    } else if (LockingMode == LM_LEGACY) {
      // get address of the stack lock
      __ la(x10, Address(sp, lock_slot_offset * VMRegImpl::stack_slot_size));
      //  get old displaced header
      __ ld(old_hdr, Address(x10, 0));

      // Atomic swap old header if oop still contains the stack lock
      Label count;
      __ cmpxchg_obj_header(x10, old_hdr, obj_reg, lock_tmp, count, &slow_path_unlock);
      __ bind(count);
      __ dec_held_monitor_count(t0);
    } else {
      assert(LockingMode == LM_LIGHTWEIGHT, "");
      __ lightweight_unlock(obj_reg, old_hdr, swap_reg, lock_tmp, slow_path_unlock);
    }

    // slow path re-enters here
    __ bind(unlock_done);
    if (ret_type != T_FLOAT && ret_type != T_DOUBLE && ret_type != T_VOID) {
      restore_native_result(masm, ret_type, stack_slots);
    }

    __ bind(done);
  }

  Label dtrace_method_exit, dtrace_method_exit_done;
  if (DTraceMethodProbes) {
    __ j(dtrace_method_exit);
    __ bind(dtrace_method_exit_done);
  }

  __ reset_last_Java_frame(false);

  // Unbox oop result, e.g. JNIHandles::resolve result.
  if (is_reference_type(ret_type)) {
    __ resolve_jobject(x10, x11, x12);
  }

  if (CheckJNICalls) {
    // clear_pending_jni_exception_check
    __ sd(zr, Address(xthread, JavaThread::pending_jni_exception_check_fn_offset()));
  }

  // reset handle block
  __ ld(x12, Address(xthread, JavaThread::active_handles_offset()));
  __ sd(zr, Address(x12, JNIHandleBlock::top_offset()));

  __ leave();

  #if INCLUDE_JFR
  // We need to do a poll test after unwind in case the sampler
  // managed to sample the native frame after returning to Java.
  Label L_return;
  __ ld(t0, Address(xthread, JavaThread::polling_word_offset()));
  address poll_test_pc = __ pc();
  __ relocate(relocInfo::poll_return_type);
  __ test_bit(t0, t0, log2i_exact(SafepointMechanism::poll_bit()));
  __ beqz(t0, L_return);
  assert(SharedRuntime::polling_page_return_handler_blob() != nullptr,
         "polling page return stub not created yet");
  address stub = SharedRuntime::polling_page_return_handler_blob()->entry_point();
  __ la(t0, InternalAddress(poll_test_pc));
  __ sd(t0, Address(xthread, JavaThread::saved_exception_pc_offset()));
  __ far_jump(RuntimeAddress(stub));
  __ bind(L_return);
#endif // INCLUDE_JFR

  // Any exception pending?
  Label exception_pending;
  __ ld(t0, Address(xthread, in_bytes(Thread::pending_exception_offset())));
  __ bnez(t0, exception_pending);

  // We're done
  __ ret();

  // Unexpected paths are out of line and go here

  // forward the exception
  __ bind(exception_pending);

  // and forward the exception
  __ far_jump(RuntimeAddress(StubRoutines::forward_exception_entry()));

  // Slow path locking & unlocking
  if (method->is_synchronized()) {

    __ block_comment("Slow path lock {");
    __ bind(slow_path_lock);

    // has last_Java_frame setup. No exceptions so do vanilla call not call_VM
    // args are (oop obj, BasicLock* lock, JavaThread* thread)

    // protect the args we've loaded
    save_args(masm, total_c_args, c_arg, out_regs);

    __ mv(c_rarg0, obj_reg);
    __ mv(c_rarg1, lock_reg);
    __ mv(c_rarg2, xthread);

    // Not a leaf but we have last_Java_frame setup as we want.
    // We don't want to unmount in case of contention since that would complicate preserving
    // the arguments that had already been marshalled into the native convention. So we force
    // the freeze slow path to find this native wrapper frame (see recurse_freeze_native_frame())
    // and pin the vthread. Otherwise the fast path won't find it since we don't walk the stack.
    __ push_cont_fastpath();
    __ call_VM_leaf(CAST_FROM_FN_PTR(address, SharedRuntime::complete_monitor_locking_C), 3);
    __ pop_cont_fastpath();
    restore_args(masm, total_c_args, c_arg, out_regs);

#ifdef ASSERT
    { Label L;
      __ ld(t0, Address(xthread, in_bytes(Thread::pending_exception_offset())));
      __ beqz(t0, L);
      __ stop("no pending exception allowed on exit from monitorenter");
      __ bind(L);
    }
#endif
    __ j(lock_done);

    __ block_comment("} Slow path lock");

    __ block_comment("Slow path unlock {");
    __ bind(slow_path_unlock);

    if (ret_type == T_FLOAT || ret_type == T_DOUBLE) {
      save_native_result(masm, ret_type, stack_slots);
    }

    __ mv(c_rarg2, xthread);
    __ la(c_rarg1, Address(sp, lock_slot_offset * VMRegImpl::stack_slot_size));
    __ mv(c_rarg0, obj_reg);

    // Save pending exception around call to VM (which contains an EXCEPTION_MARK)
    // NOTE that obj_reg == x9 currently
    __ ld(x9, Address(xthread, in_bytes(Thread::pending_exception_offset())));
    __ sd(zr, Address(xthread, in_bytes(Thread::pending_exception_offset())));

    __ rt_call(CAST_FROM_FN_PTR(address, SharedRuntime::complete_monitor_unlocking_C));

#ifdef ASSERT
    {
      Label L;
      __ ld(t0, Address(xthread, in_bytes(Thread::pending_exception_offset())));
      __ beqz(t0, L);
      __ stop("no pending exception allowed on exit complete_monitor_unlocking_C");
      __ bind(L);
    }
#endif /* ASSERT */

    __ sd(x9, Address(xthread, in_bytes(Thread::pending_exception_offset())));

    if (ret_type == T_FLOAT || ret_type == T_DOUBLE) {
      restore_native_result(masm, ret_type, stack_slots);
    }
    __ j(unlock_done);

    __ block_comment("} Slow path unlock");

  } // synchronized

  // SLOW PATH Reguard the stack if needed

  __ bind(reguard);
  save_native_result(masm, ret_type, stack_slots);
  __ rt_call(CAST_FROM_FN_PTR(address, SharedRuntime::reguard_yellow_pages));
  restore_native_result(masm, ret_type, stack_slots);
  // and continue
  __ j(reguard_done);

  // SLOW PATH safepoint
  {
    __ block_comment("safepoint {");
    __ bind(safepoint_in_progress);

    // Don't use call_VM as it will see a possible pending exception and forward it
    // and never return here preventing us from clearing _last_native_pc down below.
    //
    save_native_result(masm, ret_type, stack_slots);
    __ mv(c_rarg0, xthread);
#ifndef PRODUCT
    assert(frame::arg_reg_save_area_bytes == 0, "not expecting frame reg save area");
#endif
    __ rt_call(CAST_FROM_FN_PTR(address, JavaThread::check_special_condition_for_native_trans));

    // Restore any method result value
    restore_native_result(masm, ret_type, stack_slots);

    __ j(safepoint_in_progress_done);
    __ block_comment("} safepoint");
  }

  // SLOW PATH dtrace support
  if (DTraceMethodProbes) {
    {
      __ block_comment("dtrace entry {");
      __ bind(dtrace_method_entry);

      // We have all of the arguments setup at this point. We must not touch any register
      // argument registers at this point (what if we save/restore them there are no oop?

      save_args(masm, total_c_args, c_arg, out_regs);
      __ mov_metadata(c_rarg1, method());
      __ call_VM_leaf(
        CAST_FROM_FN_PTR(address, SharedRuntime::dtrace_method_entry),
        xthread, c_rarg1);
      restore_args(masm, total_c_args, c_arg, out_regs);
      __ j(dtrace_method_entry_done);
      __ block_comment("} dtrace entry");
    }

    {
      __ block_comment("dtrace exit {");
      __ bind(dtrace_method_exit);
      save_native_result(masm, ret_type, stack_slots);
      __ mov_metadata(c_rarg1, method());
      __ call_VM_leaf(
           CAST_FROM_FN_PTR(address, SharedRuntime::dtrace_method_exit),
           xthread, c_rarg1);
      restore_native_result(masm, ret_type, stack_slots);
      __ j(dtrace_method_exit_done);
      __ block_comment("} dtrace exit");
    }
  }

  __ flush();

  nmethod *nm = nmethod::new_native_nmethod(method,
                                            compile_id,
                                            masm->code(),
                                            vep_offset,
                                            frame_complete,
                                            stack_slots / VMRegImpl::slots_per_word,
                                            (is_static ? in_ByteSize(klass_offset) : in_ByteSize(receiver_offset)),
                                            in_ByteSize(lock_slot_offset*VMRegImpl::stack_slot_size),
                                            oop_maps);
  assert(nm != nullptr, "create native nmethod fail!");
  return nm;
}

// this function returns the adjust size (in number of words) to a c2i adapter
// activation for use during deoptimization
int Deoptimization::last_frame_adjust(int callee_parameters, int callee_locals) {
  assert(callee_locals >= callee_parameters,
         "test and remove; got more parms than locals");
  if (callee_locals < callee_parameters) {
    return 0;                   // No adjustment for negative locals
  }
  int diff = (callee_locals - callee_parameters) * Interpreter::stackElementWords;
  // diff is counted in stack words
  return align_up(diff, 2);
}

//------------------------------generate_deopt_blob----------------------------
void SharedRuntime::generate_deopt_blob() {
  // Allocate space for the code
  ResourceMark rm;
  // Setup code generation tools
  int pad = 0;
#if INCLUDE_JVMCI
  if (EnableJVMCI) {
    pad += 512; // Increase the buffer size when compiling for JVMCI
  }
#endif
  const char* name = SharedRuntime::stub_name(SharedStubId::deopt_id);
  CodeBuffer buffer(name, 2048 + pad, 1024);
  MacroAssembler* masm = new MacroAssembler(&buffer);
  int frame_size_in_words = -1;
  OopMap* map = nullptr;
  OopMapSet *oop_maps = new OopMapSet();
  assert_cond(masm != nullptr && oop_maps != nullptr);
  RegisterSaver reg_saver(COMPILER2_OR_JVMCI != 0);

  // -------------
  // This code enters when returning to a de-optimized nmethod.  A return
  // address has been pushed on the stack, and return values are in
  // registers.
  // If we are doing a normal deopt then we were called from the patched
  // nmethod from the point we returned to the nmethod. So the return
  // address on the stack is wrong by NativeCall::instruction_size
  // We will adjust the value so it looks like we have the original return
  // address on the stack (like when we eagerly deoptimized).
  // In the case of an exception pending when deoptimizing, we enter
  // with a return address on the stack that points after the call we patched
  // into the exception handler. We have the following register state from,
  // e.g., the forward exception stub (see stubGenerator_riscv.cpp).
  //    x10: exception oop
  //    x9: exception handler
  //    x13: throwing pc
  // So in this case we simply jam x13 into the useless return address and
  // the stack looks just like we want.
  //
  // At this point we need to de-opt.  We save the argument return
  // registers.  We call the first C routine, fetch_unroll_info().  This
  // routine captures the return values and returns a structure which
  // describes the current frame size and the sizes of all replacement frames.
  // The current frame is compiled code and may contain many inlined
  // functions, each with their own JVM state.  We pop the current frame, then
  // push all the new frames.  Then we call the C routine unpack_frames() to
  // populate these frames.  Finally unpack_frames() returns us the new target
  // address.  Notice that callee-save registers are BLOWN here; they have
  // already been captured in the vframeArray at the time the return PC was
  // patched.
  address start = __ pc();
  Label cont;

  // Prolog for non exception case!

  // Save everything in sight.
  map = reg_saver.save_live_registers(masm, 0, &frame_size_in_words);

  // Normal deoptimization.  Save exec mode for unpack_frames.
  __ mv(xcpool, Deoptimization::Unpack_deopt); // callee-saved
  __ j(cont);

  int reexecute_offset = __ pc() - start;
#if INCLUDE_JVMCI && !defined(COMPILER1)
  if (UseJVMCICompiler) {
    // JVMCI does not use this kind of deoptimization
    __ should_not_reach_here();
  }
#endif

  // Reexecute case
  // return address is the pc describes what bci to do re-execute at

  // No need to update map as each call to save_live_registers will produce identical oopmap
  (void) reg_saver.save_live_registers(masm, 0, &frame_size_in_words);

  __ mv(xcpool, Deoptimization::Unpack_reexecute); // callee-saved
  __ j(cont);

#if INCLUDE_JVMCI
  Label after_fetch_unroll_info_call;
  int implicit_exception_uncommon_trap_offset = 0;
  int uncommon_trap_offset = 0;

  if (EnableJVMCI) {
    implicit_exception_uncommon_trap_offset = __ pc() - start;

    __ ld(ra, Address(xthread, in_bytes(JavaThread::jvmci_implicit_exception_pc_offset())));
    __ sd(zr, Address(xthread, in_bytes(JavaThread::jvmci_implicit_exception_pc_offset())));

    uncommon_trap_offset = __ pc() - start;

    // Save everything in sight.
    reg_saver.save_live_registers(masm, 0, &frame_size_in_words);
    // fetch_unroll_info needs to call last_java_frame()
    Label retaddr;
    __ set_last_Java_frame(sp, noreg, retaddr, t0);

    __ lw(c_rarg1, Address(xthread, in_bytes(JavaThread::pending_deoptimization_offset())));
    __ mv(t0, -1);
    __ sw(t0, Address(xthread, in_bytes(JavaThread::pending_deoptimization_offset())));

    __ mv(xcpool, Deoptimization::Unpack_reexecute);
    __ mv(c_rarg0, xthread);
    __ orrw(c_rarg2, zr, xcpool); // exec mode
    __ rt_call(CAST_FROM_FN_PTR(address, Deoptimization::uncommon_trap));
    __ bind(retaddr);
    oop_maps->add_gc_map( __ pc()-start, map->deep_copy());

    __ reset_last_Java_frame(false);

    __ j(after_fetch_unroll_info_call);
  } // EnableJVMCI
#endif // INCLUDE_JVMCI

  int exception_offset = __ pc() - start;

  // Prolog for exception case

  // all registers are dead at this entry point, except for x10, and
  // x13 which contain the exception oop and exception pc
  // respectively.  Set them in TLS and fall thru to the
  // unpack_with_exception_in_tls entry point.

  __ sd(x13, Address(xthread, JavaThread::exception_pc_offset()));
  __ sd(x10, Address(xthread, JavaThread::exception_oop_offset()));

  int exception_in_tls_offset = __ pc() - start;

  // new implementation because exception oop is now passed in JavaThread

  // Prolog for exception case
  // All registers must be preserved because they might be used by LinearScan
  // Exceptiop oop and throwing PC are passed in JavaThread
  // tos: stack at point of call to method that threw the exception (i.e. only
  // args are on the stack, no return address)

  // The return address pushed by save_live_registers will be patched
  // later with the throwing pc. The correct value is not available
  // now because loading it from memory would destroy registers.

  // NB: The SP at this point must be the SP of the method that is
  // being deoptimized.  Deoptimization assumes that the frame created
  // here by save_live_registers is immediately below the method's SP.
  // This is a somewhat fragile mechanism.

  // Save everything in sight.
  map = reg_saver.save_live_registers(masm, 0, &frame_size_in_words);

  // Now it is safe to overwrite any register

  // Deopt during an exception.  Save exec mode for unpack_frames.
  __ mv(xcpool, Deoptimization::Unpack_exception); // callee-saved

  // load throwing pc from JavaThread and patch it as the return address
  // of the current frame. Then clear the field in JavaThread

  __ ld(x13, Address(xthread, JavaThread::exception_pc_offset()));
  __ sd(x13, Address(fp, frame::return_addr_offset * wordSize));
  __ sd(zr, Address(xthread, JavaThread::exception_pc_offset()));

#ifdef ASSERT
  // verify that there is really an exception oop in JavaThread
  __ ld(x10, Address(xthread, JavaThread::exception_oop_offset()));
  __ verify_oop(x10);

  // verify that there is no pending exception
  Label no_pending_exception;
  __ ld(t0, Address(xthread, Thread::pending_exception_offset()));
  __ beqz(t0, no_pending_exception);
  __ stop("must not have pending exception here");
  __ bind(no_pending_exception);
#endif

  __ bind(cont);

  // Call C code.  Need thread and this frame, but NOT official VM entry
  // crud.  We cannot block on this call, no GC can happen.
  //
  // UnrollBlock* fetch_unroll_info(JavaThread* thread)

  // fetch_unroll_info needs to call last_java_frame().

  Label retaddr;
  __ set_last_Java_frame(sp, noreg, retaddr, t0);
#ifdef ASSERT
  {
    Label L;
    __ ld(t0, Address(xthread,
                              JavaThread::last_Java_fp_offset()));
    __ beqz(t0, L);
    __ stop("SharedRuntime::generate_deopt_blob: last_Java_fp not cleared");
    __ bind(L);
  }
#endif // ASSERT
  __ mv(c_rarg0, xthread);
  __ mv(c_rarg1, xcpool);
  __ rt_call(CAST_FROM_FN_PTR(address, Deoptimization::fetch_unroll_info));
  __ bind(retaddr);

  // Need to have an oopmap that tells fetch_unroll_info where to
  // find any register it might need.
  oop_maps->add_gc_map(__ pc() - start, map);

  __ reset_last_Java_frame(false);

#if INCLUDE_JVMCI
  if (EnableJVMCI) {
    __ bind(after_fetch_unroll_info_call);
  }
#endif

  // Load UnrollBlock* into x15
  __ mv(x15, x10);

  __ lwu(xcpool, Address(x15, Deoptimization::UnrollBlock::unpack_kind_offset()));
  Label noException;
  __ mv(t0, Deoptimization::Unpack_exception);
  __ bne(xcpool, t0, noException); // Was exception pending?
  __ ld(x10, Address(xthread, JavaThread::exception_oop_offset()));
  __ ld(x13, Address(xthread, JavaThread::exception_pc_offset()));
  __ sd(zr, Address(xthread, JavaThread::exception_oop_offset()));
  __ sd(zr, Address(xthread, JavaThread::exception_pc_offset()));

  __ verify_oop(x10);

  // Overwrite the result registers with the exception results.
  __ sd(x10, Address(sp, reg_saver.reg_offset_in_bytes(x10)));

  __ bind(noException);

  // Only register save data is on the stack.
  // Now restore the result registers.  Everything else is either dead
  // or captured in the vframeArray.

  // Restore fp result register
  __ fld(f10, Address(sp, reg_saver.freg_offset_in_bytes(f10)));
  // Restore integer result register
  __ ld(x10, Address(sp, reg_saver.reg_offset_in_bytes(x10)));

  // Pop all of the register save area off the stack
  __ add(sp, sp, frame_size_in_words * wordSize);

  // All of the register save area has been popped of the stack. Only the
  // return address remains.

  // Pop all the frames we must move/replace.
  //
  // Frame picture (youngest to oldest)
  // 1: self-frame (no frame link)
  // 2: deopting frame  (no frame link)
  // 3: caller of deopting frame (could be compiled/interpreted).
  //
  // Note: by leaving the return address of self-frame on the stack
  // and using the size of frame 2 to adjust the stack
  // when we are done the return to frame 3 will still be on the stack.

  // Pop deoptimized frame
  __ lwu(x12, Address(x15, Deoptimization::UnrollBlock::size_of_deoptimized_frame_offset()));
  __ subi(x12, x12, 2 * wordSize);
  __ add(sp, sp, x12);
  __ ld(fp, Address(sp, 0));
  __ ld(ra, Address(sp, wordSize));
  __ addi(sp, sp, 2 * wordSize);
  // RA should now be the return address to the caller (3)

#ifdef ASSERT
  // Compilers generate code that bang the stack by as much as the
  // interpreter would need. So this stack banging should never
  // trigger a fault. Verify that it does not on non product builds.
  __ lwu(x9, Address(x15, Deoptimization::UnrollBlock::total_frame_sizes_offset()));
  __ bang_stack_size(x9, x12);
#endif
  // Load address of array of frame pcs into x12
  __ ld(x12, Address(x15, Deoptimization::UnrollBlock::frame_pcs_offset()));

  // Load address of array of frame sizes into x14
  __ ld(x14, Address(x15, Deoptimization::UnrollBlock::frame_sizes_offset()));

  // Load counter into x13
  __ lwu(x13, Address(x15, Deoptimization::UnrollBlock::number_of_frames_offset()));

  // Now adjust the caller's stack to make up for the extra locals
  // but record the original sp so that we can save it in the skeletal interpreter
  // frame and the stack walking of interpreter_sender will get the unextended sp
  // value and not the "real" sp value.

  const Register sender_sp = x16;

  __ mv(sender_sp, sp);
  __ lwu(x9, Address(x15,
                     Deoptimization::UnrollBlock::
                     caller_adjustment_offset()));
  __ sub(sp, sp, x9);

  // Push interpreter frames in a loop
  __ mv(t0, 0xDEADDEAD);               // Make a recognizable pattern
  __ mv(t1, t0);
  Label loop;
  __ bind(loop);
  __ ld(x9, Address(x14, 0));          // Load frame size
  __ addi(x14, x14, wordSize);
  __ subi(x9, x9, 2 * wordSize);       // We'll push pc and fp by hand
  __ ld(ra, Address(x12, 0));          // Load pc
  __ addi(x12, x12, wordSize);
  __ enter();                          // Save old & set new fp
  __ sub(sp, sp, x9);                  // Prolog
  // This value is corrected by layout_activation_impl
  __ sd(zr, Address(fp, frame::interpreter_frame_last_sp_offset * wordSize));
  __ sd(sender_sp, Address(fp, frame::interpreter_frame_sender_sp_offset * wordSize)); // Make it walkable
  __ mv(sender_sp, sp);                // Pass sender_sp to next frame
  __ subi(x13, x13, 1);                // Decrement counter
  __ bnez(x13, loop);

    // Re-push self-frame
  __ ld(ra, Address(x12));
  __ enter();

  // Allocate a full sized register save area.  We subtract 2 because
  // enter() just pushed 2 words
  __ sub(sp, sp, (frame_size_in_words - 2) * wordSize);

  // Restore frame locals after moving the frame
  __ fsd(f10, Address(sp, reg_saver.freg_offset_in_bytes(f10)));
  __ sd(x10, Address(sp, reg_saver.reg_offset_in_bytes(x10)));

  // Call C code.  Need thread but NOT official VM entry
  // crud.  We cannot block on this call, no GC can happen.  Call should
  // restore return values to their stack-slots with the new SP.
  //
  // void Deoptimization::unpack_frames(JavaThread* thread, int exec_mode)

  // Use fp because the frames look interpreted now
  // Don't need the precise return PC here, just precise enough to point into this code blob.
  address the_pc = __ pc();
  __ set_last_Java_frame(sp, fp, the_pc, t0);

  __ mv(c_rarg0, xthread);
  __ mv(c_rarg1, xcpool); // second arg: exec_mode
  __ rt_call(CAST_FROM_FN_PTR(address, Deoptimization::unpack_frames));

  // Set an oopmap for the call site
  // Use the same PC we used for the last java frame
  oop_maps->add_gc_map(the_pc - start,
                       new OopMap(frame_size_in_words, 0));

  // Clear fp AND pc
  __ reset_last_Java_frame(true);

  // Collect return values
  __ fld(f10, Address(sp, reg_saver.freg_offset_in_bytes(f10)));
  __ ld(x10, Address(sp, reg_saver.reg_offset_in_bytes(x10)));

  // Pop self-frame.
  __ leave();                           // Epilog

  // Jump to interpreter
  __ ret();

  // Make sure all code is generated
  masm->flush();

  _deopt_blob = DeoptimizationBlob::create(&buffer, oop_maps, 0, exception_offset, reexecute_offset, frame_size_in_words);
  assert(_deopt_blob != nullptr, "create deoptimization blob fail!");
  _deopt_blob->set_unpack_with_exception_in_tls_offset(exception_in_tls_offset);
#if INCLUDE_JVMCI
  if (EnableJVMCI) {
    _deopt_blob->set_uncommon_trap_offset(uncommon_trap_offset);
    _deopt_blob->set_implicit_exception_uncommon_trap_offset(implicit_exception_uncommon_trap_offset);
  }
#endif
}

// Number of stack slots between incoming argument block and the start of
// a new frame. The PROLOG must add this many slots to the stack. The
// EPILOG must remove this many slots.
// RISCV needs two words for RA (return address) and FP (frame pointer).
uint SharedRuntime::in_preserve_stack_slots() {
  return 2 * VMRegImpl::slots_per_word;
}

uint SharedRuntime::out_preserve_stack_slots() {
  return 0;
}

VMReg SharedRuntime::thread_register() {
  return xthread->as_VMReg();
}

//------------------------------generate_handler_blob------
//
// Generate a special Compile2Runtime blob that saves all registers,
// and setup oopmap.
//
SafepointBlob* SharedRuntime::generate_handler_blob(SharedStubId id, address call_ptr) {
  assert(is_polling_page_id(id), "expected a polling page stub id");

  ResourceMark rm;
  OopMapSet *oop_maps = new OopMapSet();
  assert_cond(oop_maps != nullptr);
  OopMap* map = nullptr;

  // Allocate space for the code.  Setup code generation tools.
  const char* name = SharedRuntime::stub_name(id);
  CodeBuffer buffer(name, 2048, 1024);
  MacroAssembler* masm = new MacroAssembler(&buffer);
  assert_cond(masm != nullptr);

  address start   = __ pc();
  address call_pc = nullptr;
  int frame_size_in_words = -1;
  bool cause_return = (id == SharedStubId::polling_page_return_handler_id);
  RegisterSaver reg_saver(id == SharedStubId::polling_page_vectors_safepoint_handler_id /* save_vectors */);

  // Save Integer and Float registers.
  map = reg_saver.save_live_registers(masm, 0, &frame_size_in_words);

  // The following is basically a call_VM.  However, we need the precise
  // address of the call in order to generate an oopmap. Hence, we do all the
  // work ourselves.

  Label retaddr;
  __ set_last_Java_frame(sp, noreg, retaddr, t0);

  // The return address must always be correct so that frame constructor never
  // sees an invalid pc.

  if (!cause_return) {
    // overwrite the return address pushed by save_live_registers
    // Additionally, x18 is a callee-saved register so we can look at
    // it later to determine if someone changed the return address for
    // us!
    __ ld(x18, Address(xthread, JavaThread::saved_exception_pc_offset()));
    __ sd(x18, Address(fp, frame::return_addr_offset * wordSize));
  }

  // Do the call
  __ mv(c_rarg0, xthread);
  __ rt_call(call_ptr);
  __ bind(retaddr);

  // Set an oopmap for the call site.  This oopmap will map all
  // oop-registers and debug-info registers as callee-saved.  This
  // will allow deoptimization at this safepoint to find all possible
  // debug-info recordings, as well as let GC find all oops.

  oop_maps->add_gc_map( __ pc() - start, map);

  Label noException;

  __ reset_last_Java_frame(false);

  __ membar(MacroAssembler::LoadLoad | MacroAssembler::LoadStore);

  __ ld(t0, Address(xthread, Thread::pending_exception_offset()));
  __ beqz(t0, noException);

  // Exception pending

  reg_saver.restore_live_registers(masm);

  __ far_jump(RuntimeAddress(StubRoutines::forward_exception_entry()));

  // No exception case
  __ bind(noException);

  Label no_adjust, bail;
  if (!cause_return) {
    // If our stashed return pc was modified by the runtime we avoid touching it
    __ ld(t0, Address(fp, frame::return_addr_offset * wordSize));
    __ bne(x18, t0, no_adjust);

#ifdef ASSERT
    // Verify the correct encoding of the poll we're about to skip.
    // See NativeInstruction::is_lwu_to_zr()
    __ lwu(t0, Address(x18));
    __ andi(t1, t0, 0b1111111);
    __ mv(t2, 0b0000011);
    __ bne(t1, t2, bail); // 0-6:0b0000011
    __ srli(t1, t0, 7);
    __ andi(t1, t1, 0b11111);
    __ bnez(t1, bail);    // 7-11:0b00000
    __ srli(t1, t0, 12);
    __ andi(t1, t1, 0b111);
    __ mv(t2, 0b110);
    __ bne(t1, t2, bail); // 12-14:0b110
#endif

    // Adjust return pc forward to step over the safepoint poll instruction
    __ addi(x18, x18, NativeInstruction::instruction_size);
    __ sd(x18, Address(fp, frame::return_addr_offset * wordSize));
  }

  __ bind(no_adjust);
  // Normal exit, restore registers and exit.

  reg_saver.restore_live_registers(masm);
  __ ret();

#ifdef ASSERT
  __ bind(bail);
  __ stop("Attempting to adjust pc to skip safepoint poll but the return point is not what we expected");
#endif

  // Make sure all code is generated
  masm->flush();

  // Fill-out other meta info
  return SafepointBlob::create(&buffer, oop_maps, frame_size_in_words);
}

//
// generate_resolve_blob - call resolution (static/virtual/opt-virtual/ic-miss
//
// Generate a stub that calls into vm to find out the proper destination
// of a java call. All the argument registers are live at this point
// but since this is generic code we don't know what they are and the caller
// must do any gc of the args.
//
RuntimeStub* SharedRuntime::generate_resolve_blob(SharedStubId id, address destination) {
  assert(StubRoutines::forward_exception_entry() != nullptr, "must be generated before");
  assert(is_resolve_id(id), "expected a resolve stub id");

  // allocate space for the code
  ResourceMark rm;

  const char* name = SharedRuntime::stub_name(id);
  CodeBuffer buffer(name, 1000, 512);
  MacroAssembler* masm = new MacroAssembler(&buffer);
  assert_cond(masm != nullptr);

  int frame_size_in_words = -1;
  RegisterSaver reg_saver(false /* save_vectors */);

  OopMapSet *oop_maps = new OopMapSet();
  assert_cond(oop_maps != nullptr);
  OopMap* map = nullptr;

  int start = __ offset();

  map = reg_saver.save_live_registers(masm, 0, &frame_size_in_words);

  int frame_complete = __ offset();

  {
    Label retaddr;
    __ set_last_Java_frame(sp, noreg, retaddr, t0);

    __ mv(c_rarg0, xthread);
    __ rt_call(destination);
    __ bind(retaddr);
  }

  // Set an oopmap for the call site.
  // We need this not only for callee-saved registers, but also for volatile
  // registers that the compiler might be keeping live across a safepoint.

  oop_maps->add_gc_map( __ offset() - start, map);

  // x10 contains the address we are going to jump to assuming no exception got installed

  // clear last_Java_sp
  __ reset_last_Java_frame(false);
  // check for pending exceptions
  Label pending;
  __ ld(t1, Address(xthread, Thread::pending_exception_offset()));
  __ bnez(t1, pending);

  // get the returned Method*
  __ get_vm_result_metadata(xmethod, xthread);
  __ sd(xmethod, Address(sp, reg_saver.reg_offset_in_bytes(xmethod)));

  // x10 is where we want to jump, overwrite t1 which is saved and temporary
  __ sd(x10, Address(sp, reg_saver.reg_offset_in_bytes(t1)));
  reg_saver.restore_live_registers(masm);

  // We are back to the original state on entry and ready to go.
  __ jr(t1);

  // Pending exception after the safepoint

  __ bind(pending);

  reg_saver.restore_live_registers(masm);

  // exception pending => remove activation and forward to exception handler

  __ sd(zr, Address(xthread, JavaThread::vm_result_oop_offset()));

  __ ld(x10, Address(xthread, Thread::pending_exception_offset()));
  __ far_jump(RuntimeAddress(StubRoutines::forward_exception_entry()));

  // -------------
  // make sure all code is generated
  masm->flush();

  // return the  blob
  return RuntimeStub::new_runtime_stub(name, &buffer, frame_complete, frame_size_in_words, oop_maps, true);
}

// Continuation point for throwing of implicit exceptions that are
// not handled in the current activation. Fabricates an exception
// oop and initiates normal exception dispatching in this
// frame. Since we need to preserve callee-saved values (currently
// only for C2, but done for C1 as well) we need a callee-saved oop
// map and therefore have to make these stubs into RuntimeStubs
// rather than BufferBlobs.  If the compiler needs all registers to
// be preserved between the fault point and the exception handler
// then it must assume responsibility for that in
// AbstractCompiler::continuation_for_implicit_null_exception or
// continuation_for_implicit_division_by_zero_exception. All other
// implicit exceptions (e.g., NullPointerException or
// AbstractMethodError on entry) are either at call sites or
// otherwise assume that stack unwinding will be initiated, so
// caller saved registers were assumed volatile in the compiler.

RuntimeStub* SharedRuntime::generate_throw_exception(SharedStubId id, address runtime_entry) {
  assert(is_throw_id(id), "expected a throw stub id");

  const char* name = SharedRuntime::stub_name(id);

  // Information about frame layout at time of blocking runtime call.
  // Note that we only have to preserve callee-saved registers since
  // the compilers are responsible for supplying a continuation point
  // if they expect all registers to be preserved.
  // n.b. riscv asserts that frame::arg_reg_save_area_bytes == 0
  assert_cond(runtime_entry != nullptr);
  enum layout {
    fp_off = 0,
    fp_off2,
    return_off,
    return_off2,
    framesize // inclusive of return address
  };

  const int insts_size = 1024;
  const int locs_size  = 64;

  ResourceMark rm;
  const char* timer_msg = "SharedRuntime generate_throw_exception";
  TraceTime timer(timer_msg, TRACETIME_LOG(Info, startuptime));

  CodeBuffer code(name, insts_size, locs_size);
  OopMapSet* oop_maps  = new OopMapSet();
  MacroAssembler* masm = new MacroAssembler(&code);
  assert_cond(oop_maps != nullptr && masm != nullptr);

  address start = __ pc();

  // This is an inlined and slightly modified version of call_VM
  // which has the ability to fetch the return PC out of
  // thread-local storage and also sets up last_Java_sp slightly
  // differently than the real call_VM

  __ enter(); // Save FP and RA before call

  assert(is_even(framesize / 2), "sp not 16-byte aligned");

  // ra and fp are already in place
  __ subi(sp, fp, (unsigned)framesize << LogBytesPerInt); // prolog

  int frame_complete = __ pc() - start;

  // Set up last_Java_sp and last_Java_fp
  address the_pc = __ pc();
  __ set_last_Java_frame(sp, fp, the_pc, t0);

  // Call runtime
  __ mv(c_rarg0, xthread);
  BLOCK_COMMENT("call runtime_entry");
  __ rt_call(runtime_entry);

  // Generate oop map
  OopMap* map = new OopMap(framesize, 0);
  assert_cond(map != nullptr);

  oop_maps->add_gc_map(the_pc - start, map);

  __ reset_last_Java_frame(true);

  __ leave();

  // check for pending exceptions
#ifdef ASSERT
  Label L;
  __ ld(t0, Address(xthread, Thread::pending_exception_offset()));
  __ bnez(t0, L);
  __ should_not_reach_here();
  __ bind(L);
#endif // ASSERT
  __ far_jump(RuntimeAddress(StubRoutines::forward_exception_entry()));

  // codeBlob framesize is in words (not VMRegImpl::slot_size)
  RuntimeStub* stub =
    RuntimeStub::new_runtime_stub(name,
                                  &code,
                                  frame_complete,
                                  (framesize >> (LogBytesPerWord - LogBytesPerInt)),
                                  oop_maps, false);
  assert(stub != nullptr, "create runtime stub fail!");
  return stub;
}

#if INCLUDE_JFR

static void jfr_prologue(address the_pc, MacroAssembler* masm, Register thread) {
  __ set_last_Java_frame(sp, fp, the_pc, t0);
  __ mv(c_rarg0, thread);
}

static void jfr_epilogue(MacroAssembler* masm) {
  __ reset_last_Java_frame(true);
}
// For c2: c_rarg0 is junk, call to runtime to write a checkpoint.
// It returns a jobject handle to the event writer.
// The handle is dereferenced and the return value is the event writer oop.
RuntimeStub* SharedRuntime::generate_jfr_write_checkpoint() {
  enum layout {
    fp_off,
    fp_off2,
    return_off,
    return_off2,
    framesize // inclusive of return address
  };

  int insts_size = 1024;
  int locs_size = 64;
  const char* name = SharedRuntime::stub_name(SharedStubId::jfr_write_checkpoint_id);
  CodeBuffer code(name, insts_size, locs_size);
  OopMapSet* oop_maps = new OopMapSet();
  MacroAssembler* masm = new MacroAssembler(&code);

  address start = __ pc();
  __ enter();
  int frame_complete = __ pc() - start;
  address the_pc = __ pc();
  jfr_prologue(the_pc, masm, xthread);
  __ call_VM_leaf(CAST_FROM_FN_PTR(address, JfrIntrinsicSupport::write_checkpoint), 1);

  jfr_epilogue(masm);
  __ resolve_global_jobject(x10, t0, t1);
  __ leave();
  __ ret();

  OopMap* map = new OopMap(framesize, 1);
  oop_maps->add_gc_map(the_pc - start, map);

  RuntimeStub* stub = // codeBlob framesize is in words (not VMRegImpl::slot_size)
    RuntimeStub::new_runtime_stub(name, &code, frame_complete,
                                  (framesize >> (LogBytesPerWord - LogBytesPerInt)),
                                  oop_maps, false);
  return stub;
}

// For c2: call to return a leased buffer.
RuntimeStub* SharedRuntime::generate_jfr_return_lease() {
  enum layout {
    fp_off,
    fp_off2,
    return_off,
    return_off2,
    framesize // inclusive of return address
  };

  int insts_size = 1024;
  int locs_size = 64;
  const char* name = SharedRuntime::stub_name(SharedStubId::jfr_return_lease_id);
  CodeBuffer code(name, insts_size, locs_size);
  OopMapSet* oop_maps = new OopMapSet();
  MacroAssembler* masm = new MacroAssembler(&code);

  address start = __ pc();
  __ enter();
  int frame_complete = __ pc() - start;
  address the_pc = __ pc();
  jfr_prologue(the_pc, masm, xthread);
  __ call_VM_leaf(CAST_FROM_FN_PTR(address, JfrIntrinsicSupport::return_lease), 1);

  jfr_epilogue(masm);
  __ leave();
  __ ret();

  OopMap* map = new OopMap(framesize, 1);
  oop_maps->add_gc_map(the_pc - start, map);

  RuntimeStub* stub = // codeBlob framesize is in words (not VMRegImpl::slot_size)
    RuntimeStub::new_runtime_stub(name, &code, frame_complete,
                                  (framesize >> (LogBytesPerWord - LogBytesPerInt)),
                                  oop_maps, false);
  return stub;
}

#endif // INCLUDE_JFR