src/hotspot/cpu/aarch64/jniFastGetField_aarch64.cpp

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * published by the Free Software Foundation.
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 * 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).
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 * 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.
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#include "asm/macroAssembler.hpp"
#include "gc/shared/barrierSet.hpp"
#include "gc/shared/barrierSetAssembler.hpp"
#include "memory/resourceArea.hpp"
#include "prims/jniFastGetField.hpp"
#include "prims/jvm_misc.hpp"
#include "prims/jvmtiExport.hpp"
#include "runtime/javaThread.inline.hpp"
#include "runtime/safepoint.hpp"
#include "runtime/threadWXSetters.inline.hpp"

#define __ masm->

#define BUFFER_SIZE 30*wordSize

// Instead of issuing a LoadLoad barrier we create an address
// dependency between loads; this might be more efficient.

// Common register usage:
// r0/v0:      result
// c_rarg0:    jni env
// c_rarg1:    obj
// c_rarg2:    jfield id

static const Register robj          = r3;
static const Register rcounter      = r4;
static const Register roffset       = r5;
static const Register rcounter_addr = r6;
static const Register result        = r7;

// On macos/aarch64 we need to ensure WXExec mode when running generated
// FastGetXXXField, as these functions can be called from WXWrite context
// (8262896).  So each FastGetXXXField is wrapped into a C++ statically
// compiled template function that optionally switches to WXExec if necessary.

#ifdef __APPLE__

static address generated_fast_get_field[T_LONG + 1 - T_BOOLEAN];

template<int BType> struct BasicTypeToJni {};
template<> struct BasicTypeToJni<T_BOOLEAN> { static const jboolean jni_type; };
template<> struct BasicTypeToJni<T_BYTE>    { static const jbyte    jni_type; };
template<> struct BasicTypeToJni<T_CHAR>    { static const jchar    jni_type; };
template<> struct BasicTypeToJni<T_SHORT>   { static const jshort   jni_type; };
template<> struct BasicTypeToJni<T_INT>     { static const jint     jni_type; };
template<> struct BasicTypeToJni<T_LONG>    { static const jlong    jni_type; };
template<> struct BasicTypeToJni<T_FLOAT>   { static const jfloat   jni_type; };
template<> struct BasicTypeToJni<T_DOUBLE>  { static const jdouble  jni_type; };

template<int BType, typename JniType = decltype(BasicTypeToJni<BType>::jni_type)>
JniType static_fast_get_field_wrapper(JNIEnv *env, jobject obj, jfieldID fieldID) {
  JavaThread* thread = JavaThread::thread_from_jni_environment(env);
  ThreadWXEnable wx(WXExec, thread);
  address get_field_addr = generated_fast_get_field[BType - T_BOOLEAN];
  return ((JniType(*)(JNIEnv *env, jobject obj, jfieldID fieldID))get_field_addr)(env, obj, fieldID);
}

template<int BType>
address JNI_FastGetField::generate_fast_get_int_field1() {
  generated_fast_get_field[BType - T_BOOLEAN] = generate_fast_get_int_field0((BasicType)BType);
  return (address)static_fast_get_field_wrapper<BType>;
}

#else // __APPLE__

template<int BType>
address JNI_FastGetField::generate_fast_get_int_field1() {
  return generate_fast_get_int_field0((BasicType)BType);
}

#endif // __APPLE__

address JNI_FastGetField::generate_fast_get_int_field0(BasicType type) {
  const char *name;
  switch (type) {
    case T_BOOLEAN: name = "jni_fast_GetBooleanField"; break;
    case T_BYTE:    name = "jni_fast_GetByteField";    break;
    case T_CHAR:    name = "jni_fast_GetCharField";    break;
    case T_SHORT:   name = "jni_fast_GetShortField";   break;
    case T_INT:     name = "jni_fast_GetIntField";     break;
    case T_LONG:    name = "jni_fast_GetLongField";    break;
    case T_FLOAT:   name = "jni_fast_GetFloatField";   break;
    case T_DOUBLE:  name = "jni_fast_GetDoubleField";  break;
    default:        ShouldNotReachHere();
      name = nullptr;  // unreachable
  }
  ResourceMark rm;
  BufferBlob* blob = BufferBlob::create(name, BUFFER_SIZE);
  CodeBuffer cbuf(blob);
  MacroAssembler* masm = new MacroAssembler(&cbuf);
  address fast_entry = __ pc();

  Label slow;

  uint64_t offset;
  __ adrp(rcounter_addr,
          SafepointSynchronize::safepoint_counter_addr(), offset);
  Address safepoint_counter_addr(rcounter_addr, offset);
  __ ldrw(rcounter, safepoint_counter_addr);
  __ tbnz(rcounter, 0, slow);

  // It doesn't need to issue a full barrier here even if the field
  // is volatile, since it has already used "ldar" for it.
  if (JvmtiExport::can_post_field_access()) {
    // Using barrier to order wrt. JVMTI check and load of result.
    __ membar(Assembler::LoadLoad);

    // Check to see if a field access watch has been set before we
    // take the fast path.
    uint64_t offset2;
    __ adrp(result,
            ExternalAddress((address) JvmtiExport::get_field_access_count_addr()),
            offset2);
    __ ldrw(result, Address(result, offset2));
    __ cbnzw(result, slow);

    __ mov(robj, c_rarg1);
  } else {
    // Using address dependency to order wrt. load of result.
    __ eor(robj, c_rarg1, rcounter);
    __ eor(robj, robj, rcounter);         // obj, since
                                          // robj ^ rcounter ^ rcounter == robj
                                          // robj is address dependent on rcounter.
  }

  // Both robj and rscratch1 are clobbered by try_resolve_jobject_in_native.
  BarrierSetAssembler* bs = BarrierSet::barrier_set()->barrier_set_assembler();
  bs->try_resolve_jobject_in_native(masm, c_rarg0, robj, rscratch1, slow);

  __ lsr(roffset, c_rarg2, 2);                // offset
  __ add(result, robj, roffset);

  assert(count < LIST_CAPACITY, "LIST_CAPACITY too small");
  speculative_load_pclist[count] = __ pc();   // Used by the segfault handler
  // Using acquire: Order JVMTI check and load of result wrt. succeeding check
  // (LoadStore for volatile field).
  switch (type) {
    case T_BOOLEAN: __ ldarb(result, result); break;
    case T_BYTE:    __ ldarb(result, result); __ sxtb(result, result); break;
    case T_CHAR:    __ ldarh(result, result); break;
    case T_SHORT:   __ ldarh(result, result); __ sxth(result, result); break;
    case T_FLOAT:   __ ldarw(result, result); break;
    case T_INT:     __ ldarw(result, result); __ sxtw(result, result); break;
    case T_DOUBLE:
    case T_LONG:    __ ldar (result, result); break;
    default:        ShouldNotReachHere();
  }

  __ ldrw(rscratch1, safepoint_counter_addr);
  __ cmpw(rcounter, rscratch1);
  __ br (Assembler::NE, slow);

  switch (type) {
    case T_FLOAT:   __ fmovs(v0, result); break;
    case T_DOUBLE:  __ fmovd(v0, result); break;
    default:        __ mov(r0, result);   break;
  }
  __ ret(lr);

  slowcase_entry_pclist[count++] = __ pc();
  __ bind(slow);
  address slow_case_addr;
  switch (type) {
    case T_BOOLEAN: slow_case_addr = jni_GetBooleanField_addr(); break;
    case T_BYTE:    slow_case_addr = jni_GetByteField_addr();    break;
    case T_CHAR:    slow_case_addr = jni_GetCharField_addr();    break;
    case T_SHORT:   slow_case_addr = jni_GetShortField_addr();   break;
    case T_INT:     slow_case_addr = jni_GetIntField_addr();     break;
    case T_LONG:    slow_case_addr = jni_GetLongField_addr();    break;
    case T_FLOAT:   slow_case_addr = jni_GetFloatField_addr();   break;
    case T_DOUBLE:  slow_case_addr = jni_GetDoubleField_addr();  break;
    default:        ShouldNotReachHere();
      slow_case_addr = nullptr;  // unreachable
  }

  {
    __ enter();
    __ lea(rscratch1, RuntimeAddress(slow_case_addr));
    __ blr(rscratch1);
    __ leave();
    __ ret(lr);
  }
  __ flush ();

  return fast_entry;
}

address JNI_FastGetField::generate_fast_get_boolean_field() {
  return generate_fast_get_int_field1<T_BOOLEAN>();
}

address JNI_FastGetField::generate_fast_get_byte_field() {
  return generate_fast_get_int_field1<T_BYTE>();
}

address JNI_FastGetField::generate_fast_get_char_field() {
  return generate_fast_get_int_field1<T_CHAR>();
}

address JNI_FastGetField::generate_fast_get_short_field() {
  return generate_fast_get_int_field1<T_SHORT>();
}

address JNI_FastGetField::generate_fast_get_int_field() {
  return generate_fast_get_int_field1<T_INT>();
}

address JNI_FastGetField::generate_fast_get_long_field() {
  return generate_fast_get_int_field1<T_LONG>();
}

address JNI_FastGetField::generate_fast_get_float_field() {
  return generate_fast_get_int_field1<T_FLOAT>();
}

address JNI_FastGetField::generate_fast_get_double_field() {
  return generate_fast_get_int_field1<T_DOUBLE>();
}