jdk/src/hotspot/share/runtime/stackValue.cpp

/*
 * Copyright (c) 1997, 2025, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#include "code/debugInfo.hpp"
#include "oops/access.hpp"
#include "oops/compressedOops.inline.hpp"
#include "oops/oop.hpp"
#include "runtime/frame.inline.hpp"
#include "runtime/globals.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/stackValue.hpp"
#if INCLUDE_ZGC
#include "gc/z/zBarrier.inline.hpp"
#endif
#if INCLUDE_SHENANDOAHGC
#include "gc/shenandoah/shenandoahBarrierSet.inline.hpp"
#endif

class RegisterMap;
class SmallRegisterMap;

template StackValue* StackValue::create_stack_value(const frame* fr, const RegisterMap* reg_map, ScopeValue* sv);
template StackValue* StackValue::create_stack_value(const frame* fr, const SmallRegisterMap* reg_map, ScopeValue* sv);

template<typename RegisterMapT>
StackValue* StackValue::create_stack_value(const frame* fr, const RegisterMapT* reg_map, ScopeValue* sv) {
  return create_stack_value(sv, stack_value_address(fr, reg_map, sv), reg_map);
}

static oop oop_from_oop_location(stackChunkOop chunk, void* addr) {
  if (addr == nullptr) {
    return nullptr;
  }

  if (UseCompressedOops) {
    // When compressed oops is enabled, an oop location may
    // contain narrow oop values - we deal with that here

    if (chunk != nullptr && chunk->has_bitmap()) {
      // Transformed stack chunk with narrow oops
      return chunk->load_oop((narrowOop*)addr);
    }

#ifdef _LP64
    if (CompressedOops::is_base(*(void**)addr)) {
      // Compiled code may produce decoded oop = narrow_oop_base
      // when a narrow oop implicit null check is used.
      // The narrow_oop_base could be null or be the address
      // of the page below heap. Use null value for both cases.
      return nullptr;
    }
#endif
  }

  if (chunk != nullptr) {
    // Load oop from chunk
    return chunk->load_oop((oop*)addr);
  }

  // Load oop from stack
  oop val = *(oop*)addr;

#if INCLUDE_SHENANDOAHGC
  if (UseShenandoahGC) {
    // Pass the value through the barrier to avoid capturing bad oops as
    // stack values. Note: do not heal the location, to avoid accidentally
    // corrupting the stack. Stack watermark barriers are supposed to handle
    // the healing.
    val = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(val);
  }
#endif

  return val;
}

static oop oop_from_narrowOop_location(stackChunkOop chunk, void* addr, bool is_register) {
  assert(UseCompressedOops, "Narrow oops should not exist");
  assert(addr != nullptr, "Not expecting null address");
  narrowOop* narrow_addr;
  if (is_register) {
    // The callee has no clue whether the register holds an int,
    // long or is unused.  He always saves a long.  Here we know
    // a long was saved, but we only want an int back.  Narrow the
    // saved long to the int that the JVM wants.  We can't just
    // use narrow_oop_cast directly, because we don't know what
    // the high bits of the value might be.
    narrow_addr = ((narrowOop*)addr) BIG_ENDIAN_ONLY(+ 1);
  } else {
    narrow_addr = (narrowOop*)addr;
  }

  if (chunk != nullptr) {
    // Load oop from chunk
    return chunk->load_oop(narrow_addr);
  }

  // Load oop from stack
  oop val = CompressedOops::decode(*narrow_addr);

#if INCLUDE_SHENANDOAHGC
  if (UseShenandoahGC) {
    // Pass the value through the barrier to avoid capturing bad oops as
    // stack values. Note: do not heal the location, to avoid accidentally
    // corrupting the stack. Stack watermark barriers are supposed to handle
    // the healing.
    val = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(val);
  }
#endif

  return val;
}

StackValue* StackValue::create_stack_value_from_oop_location(stackChunkOop chunk, void* addr) {
  oop val = oop_from_oop_location(chunk, addr);
  assert(oopDesc::is_oop_or_null(val), "bad oop found at " INTPTR_FORMAT " in_cont: %d compressed: %d",
         p2i(addr), chunk != nullptr, chunk != nullptr && chunk->has_bitmap() && UseCompressedOops);
  Handle h(Thread::current(), val); // Wrap a handle around the oop
  return new StackValue(h);
}

StackValue* StackValue::create_stack_value_from_narrowOop_location(stackChunkOop chunk, void* addr, bool is_register) {
  oop val = oop_from_narrowOop_location(chunk, addr, is_register);
  assert(oopDesc::is_oop_or_null(val), "bad oop found at " INTPTR_FORMAT " in_cont: %d compressed: %d",
         p2i(addr), chunk != nullptr, chunk != nullptr && chunk->has_bitmap() && UseCompressedOops);
  Handle h(Thread::current(), val); // Wrap a handle around the oop
  return new StackValue(h);
}

template<typename RegisterMapT>
StackValue* StackValue::create_stack_value(ScopeValue* sv, address value_addr, const RegisterMapT* reg_map) {
  stackChunkOop chunk = reg_map->stack_chunk()();
  if (sv->is_location()) {
    // Stack or register value
    Location loc = ((LocationValue *)sv)->location();

    // Then package it right depending on type
    // Note: the transfer of the data is thru a union that contains
    // an intptr_t. This is because an interpreter stack slot is
    // really an intptr_t. The use of a union containing an intptr_t
    // ensures that on a 64 bit platform we have proper alignment
    // and that we store the value where the interpreter will expect
    // to find it (i.e. proper endian). Similarly on a 32bit platform
    // using the intptr_t ensures that when a value is larger than
    // a stack slot (jlong/jdouble) that we capture the proper part
    // of the value for the stack slot in question.
    //
    switch( loc.type() ) {
    case Location::float_in_dbl: { // Holds a float in a double register?
      // The callee has no clue whether the register holds a float,
      // double or is unused.  He always saves a double.  Here we know
      // a double was saved, but we only want a float back.  Narrow the
      // saved double to the float that the JVM wants.
      assert( loc.is_register(), "floats always saved to stack in 1 word" );
      union { intptr_t p; jfloat jf; } value;
      value.p = (intptr_t) CONST64(0xDEADDEAFDEADDEAF);
      value.jf = (jfloat) *(jdouble*) value_addr;
      return new StackValue(value.p); // 64-bit high half is stack junk
    }
    case Location::int_in_long: { // Holds an int in a long register?
      // The callee has no clue whether the register holds an int,
      // long or is unused.  He always saves a long.  Here we know
      // a long was saved, but we only want an int back.  Narrow the
      // saved long to the int that the JVM wants.
      assert( loc.is_register(), "ints always saved to stack in 1 word" );
      union { intptr_t p; jint ji;} value;
      value.p = (intptr_t) CONST64(0xDEADDEAFDEADDEAF);
      value.ji = (jint) *(jlong*) value_addr;
      return new StackValue(value.p); // 64-bit high half is stack junk
    }
#ifdef _LP64
    case Location::dbl:
      // Double value in an aligned adjacent pair
      return new StackValue(*(intptr_t*)value_addr);
    case Location::lng:
      // Long   value in an aligned adjacent pair
      return new StackValue(*(intptr_t*)value_addr);
    case Location::narrowoop:
      return create_stack_value_from_narrowOop_location(reg_map->stack_chunk()(), (void*)value_addr, loc.is_register());
#endif
    case Location::oop:
      return create_stack_value_from_oop_location(reg_map->stack_chunk()(), (void*)value_addr);
    case Location::addr: {
      loc.print_on(tty);
      ShouldNotReachHere(); // both C1 and C2 now inline jsrs
    }
    case Location::normal: {
      // Just copy all other bits straight through
      union { intptr_t p; jint ji;} value;
      value.p = (intptr_t) CONST64(0xDEADDEAFDEADDEAF);
      value.ji = *(jint*)value_addr;
      return new StackValue(value.p);
    }
    case Location::invalid: {
      return new StackValue();
    }
    case Location::vector: {
      loc.print_on(tty);
      ShouldNotReachHere(); // should be handled by VectorSupport::allocate_vector()
    }
    default:
      loc.print_on(tty);
      ShouldNotReachHere();
    }

  } else if (sv->is_constant_int()) {
    // Constant int: treat same as register int.
    union { intptr_t p; jint ji;} value;
    value.p = (intptr_t) CONST64(0xDEADDEAFDEADDEAF);
    value.ji = (jint)((ConstantIntValue*)sv)->value();
    return new StackValue(value.p);
  } else if (sv->is_constant_oop()) {
    // constant oop
    return new StackValue(sv->as_ConstantOopReadValue()->value());
#ifdef _LP64
  } else if (sv->is_constant_double()) {
    // Constant double in a single stack slot
    union { intptr_t p; double d; } value;
    value.p = (intptr_t) CONST64(0xDEADDEAFDEADDEAF);
    value.d = ((ConstantDoubleValue *)sv)->value();
    return new StackValue(value.p);
  } else if (sv->is_constant_long()) {
    // Constant long in a single stack slot
    union { intptr_t p; jlong jl; } value;
    value.p = (intptr_t) CONST64(0xDEADDEAFDEADDEAF);
    value.jl = ((ConstantLongValue *)sv)->value();
    return new StackValue(value.p);
#endif
  } else if (sv->is_object()) { // Scalar replaced object in compiled frame
    ObjectValue* ov = (ObjectValue *)sv;
    Handle hdl = ov->value();
    return new StackValue(hdl, hdl.is_null() && ov->is_scalar_replaced() ? 1 : 0);
  } else if (sv->is_marker()) {
    // Should never need to directly construct a marker.
    ShouldNotReachHere();
  }
  // Unknown ScopeValue type
  ShouldNotReachHere();
  return new StackValue((intptr_t) 0);   // dummy
}

template address StackValue::stack_value_address(const frame* fr, const RegisterMap* reg_map, ScopeValue* sv);
template address StackValue::stack_value_address(const frame* fr, const SmallRegisterMap* reg_map, ScopeValue* sv);

template<typename RegisterMapT>
address StackValue::stack_value_address(const frame* fr, const RegisterMapT* reg_map, ScopeValue* sv) {
  if (!sv->is_location()) {
    return nullptr;
  }
  Location loc = ((LocationValue *)sv)->location();
  if (loc.type() == Location::invalid) {
    return nullptr;
  }

  if (!reg_map->in_cont()) {
    address value_addr = loc.is_register()
      // Value was in a callee-save register
      ? reg_map->location(VMRegImpl::as_VMReg(loc.register_number()), fr->sp())
      // Else value was directly saved on the stack. The frame's original stack pointer,
      // before any extension by its callee (due to Compiler1 linkage on SPARC), must be used.
      : ((address)fr->unextended_sp()) + loc.stack_offset();

    assert(value_addr == nullptr || reg_map->thread() == nullptr || reg_map->thread()->is_in_usable_stack(value_addr), INTPTR_FORMAT, p2i(value_addr));
    return value_addr;
  }

  address value_addr = loc.is_register()
    ? reg_map->as_RegisterMap()->stack_chunk()->reg_to_location(*fr, reg_map->as_RegisterMap(), VMRegImpl::as_VMReg(loc.register_number()))
    : reg_map->as_RegisterMap()->stack_chunk()->usp_offset_to_location(*fr, loc.stack_offset());

  assert(value_addr == nullptr || Continuation::is_in_usable_stack(value_addr, reg_map->as_RegisterMap()) || (reg_map->thread() != nullptr && reg_map->thread()->is_in_usable_stack(value_addr)), INTPTR_FORMAT, p2i(value_addr));
  return value_addr;
}

BasicLock* StackValue::resolve_monitor_lock(const frame& fr, Location location) {
  assert(location.is_stack(), "for now we only look at the stack");
  int word_offset = location.stack_offset() / wordSize;
  // (stack picture)
  // high: [     ]  word_offset + 1
  // low   [     ]  word_offset
  //
  // sp->  [     ]  0
  // the word_offset is the distance from the stack pointer to the lowest address
  // The frame's original stack pointer, before any extension by its callee
  // (due to Compiler1 linkage on SPARC), must be used.
  return (BasicLock*) (fr.unextended_sp() + word_offset);
}


#ifndef PRODUCT

void StackValue::print_on(outputStream* st) const {
  switch(_type) {
    case T_INT:
      st->print("%d (int) %f (float) %x (hex)",  *(int *)&_integer_value, *(float *)&_integer_value,  *(int *)&_integer_value);
      break;

    case T_OBJECT:
      if (_handle_value() != nullptr) {
        _handle_value()->print_value_on(st);
      } else {
        st->print("null");
      }
      st->print(" <" INTPTR_FORMAT ">", p2i(_handle_value()));
      break;

    case T_CONFLICT:
     st->print("conflict");
     break;

    default:
     ShouldNotReachHere();
  }
}

#endif