src/hotspot/share/oops/compressedOops.inline.hpp

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#ifndef SHARE_OOPS_COMPRESSEDOOPS_INLINE_HPP
#define SHARE_OOPS_COMPRESSEDOOPS_INLINE_HPP

#include "oops/compressedOops.hpp"

#include "memory/universe.hpp"
#include "oops/oop.hpp"
#include "utilities/align.hpp"
#include "utilities/globalDefinitions.hpp"

// Functions for encoding and decoding compressed oops.
// If the oops are compressed, the type passed to these overloaded functions
// is narrowOop.  All functions are overloaded so they can be called by
// template functions without conditionals (the compiler instantiates via
// the right type and inlines the appropriate code).

// Algorithm for encoding and decoding oops from 64 bit pointers to 32 bit
// offset from the heap base.  Saving the check for null can save instructions
// in inner GC loops so these are separated.

inline oop CompressedOops::decode_raw_not_null(narrowOop v) {
  assert(!is_null(v), "narrow oop value can never be zero");
  return decode_raw(v);
}

inline oop CompressedOops::decode_raw(narrowOop v) {
  return cast_to_oop((uintptr_t)base() + ((uintptr_t)v << shift()));
}

inline oop CompressedOops::decode_not_null(narrowOop v) {
  assert(!is_null(v), "narrow oop value can never be zero");
  oop result = decode_raw(v);
  assert(is_object_aligned(result), "address not aligned: " PTR_FORMAT, p2i(result));
  assert(Universe::is_in_heap(result), "object not in heap " PTR_FORMAT, p2i(result));
  return result;
}

inline oop CompressedOops::decode(narrowOop v) {
  return is_null(v) ? nullptr : decode_not_null(v);
}

inline narrowOop CompressedOops::encode_not_null(oop v) {
  assert(!is_null(v), "oop value can never be zero");
  assert(is_object_aligned(v), "address not aligned: " PTR_FORMAT, p2i(v));
  assert(is_in(v), "address not in heap range: " PTR_FORMAT, p2i(v));
  uint64_t  pd = (uint64_t)(pointer_delta((void*)v, (void*)base(), 1));
  assert(OopEncodingHeapMax > pd, "change encoding max if new encoding");
  narrowOop result = narrow_oop_cast(pd >> shift());
  assert(decode_raw(result) == v, "reversibility");
  return result;
}

inline narrowOop CompressedOops::encode(oop v) {
  return is_null(v) ? narrowOop::null : encode_not_null(v);
}

inline oop CompressedOops::decode_raw_not_null(oop v) {
  assert(v != nullptr, "object is null");
  return v;
}

inline oop CompressedOops::decode_not_null(oop v) {
  assert(Universe::is_in_heap(v), "object not in heap " PTR_FORMAT, p2i(v));
  return v;
}

inline oop CompressedOops::decode(oop v) {
  assert(Universe::is_in_heap_or_null(v), "object not in heap " PTR_FORMAT, p2i(v));
  return v;
}

inline narrowOop CompressedOops::encode_not_null(narrowOop v) {
  return v;
}

inline narrowOop CompressedOops::encode(narrowOop v) {
  return v;
}

inline uint32_t CompressedOops::narrow_oop_value(oop o) {
  return narrow_oop_value(encode(o));
}

inline uint32_t CompressedOops::narrow_oop_value(narrowOop o) {
  return static_cast<uint32_t>(o);
}

template<typename T>
inline narrowOop CompressedOops::narrow_oop_cast(T i) {
  static_assert(std::is_integral<T>::value, "precondition");
  uint32_t narrow_value = static_cast<uint32_t>(i);
  // Ensure no bits lost in conversion to uint32_t.
  assert(i == static_cast<T>(narrow_value), "narrowOop overflow");
  return static_cast<narrowOop>(narrow_value);
}

#endif // SHARE_OOPS_COMPRESSEDOOPS_INLINE_HPP