jerryscript/jerry-core/ecma/base/ecma-lcache.c

/* Copyright 2014-2016 Samsung Electronics Co., Ltd.
 * Copyright 2016 University of Szeged.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "ecma-gc.h"
#include "ecma-globals.h"
#include "ecma-helpers.h"
#include "ecma-lcache.h"
#include "jrt-libc-includes.h"

/** \addtogroup ecma ECMA
 * @{
 *
 * \addtogroup ecmalcache Property lookup cache
 * @{
 */

#ifndef CONFIG_ECMA_LCACHE_DISABLE
/**
 * Entry of LCache hash table
 */
typedef struct
{
  /** Pointer to a property of the object */
  ecma_property_t *prop_p;

  /** Compressed pointer to object (ECMA_NULL_POINTER marks record empty) */
  jmem_cpointer_t object_cp;

  /** Compressed pointer to property's name */
  jmem_cpointer_t prop_name_cp;
} ecma_lcache_hash_entry_t;

/**
 * Number of rows in LCache's hash table
 */
#define ECMA_LCACHE_HASH_ROWS_COUNT 128

/**
 * Number of entries in a row of LCache's hash table
 */
#define ECMA_LCACHE_HASH_ROW_LENGTH 2


/**
 * Mask for hash bits
 */
#define ECMA_LCACHE_HASH_MASK (ECMA_LCACHE_HASH_ROWS_COUNT - 1)

/**
 * LCache's hash table
 */
static ecma_lcache_hash_entry_t ecma_lcache_hash_table[ ECMA_LCACHE_HASH_ROWS_COUNT ][ ECMA_LCACHE_HASH_ROW_LENGTH ];
#endif /* !CONFIG_ECMA_LCACHE_DISABLE */

/**
 * Initialize LCache
 */
void
ecma_lcache_init (void)
{
#ifndef CONFIG_ECMA_LCACHE_DISABLE
  memset (ecma_lcache_hash_table, 0, sizeof (ecma_lcache_hash_table));
#endif /* !CONFIG_ECMA_LCACHE_DISABLE */
} /* ecma_lcache_init */

#ifndef CONFIG_ECMA_LCACHE_DISABLE
/**
 * Invalidate specified LCache entry
 */
static inline void __attr_always_inline___
ecma_lcache_invalidate_entry (ecma_lcache_hash_entry_t *entry_p) /**< entry to invalidate */
{
  JERRY_ASSERT (entry_p != NULL);
  JERRY_ASSERT (entry_p->object_cp != ECMA_NULL_POINTER);
  JERRY_ASSERT (entry_p->prop_name_cp != ECMA_NULL_POINTER);
  JERRY_ASSERT (entry_p->prop_p != NULL);

  entry_p->object_cp = ECMA_NULL_POINTER;
  ecma_set_property_lcached (entry_p->prop_p, false);
} /* ecma_lcache_invalidate_entry */

/**
 * Compute the row index of object / property name pair
 *
 * @return row index
 */
static inline size_t __attr_always_inline___
ecma_lcache_row_idx (jmem_cpointer_t object_cp, /**< compressed pointer to object */
                     const ecma_string_t *prop_name_p) /**< proeprty name */
{
  /* Randomize the hash of the property name with the object pointer using a xor operation,
   * so properties of different objects with the same name can be cached effectively. */
  return (size_t) ((ecma_string_hash (prop_name_p) ^ object_cp) & ECMA_LCACHE_HASH_MASK);
} /* ecma_lcache_row_idx */
#endif /* !CONFIG_ECMA_LCACHE_DISABLE */

/**
 * Insert an entry into LCache
 */
void
ecma_lcache_insert (ecma_object_t *object_p, /**< object */
                    ecma_string_t *prop_name_p, /**< property name */
                    ecma_property_t *prop_p) /**< property */
{
  JERRY_ASSERT (object_p != NULL);
  JERRY_ASSERT (prop_name_p != NULL);
  JERRY_ASSERT (prop_p != NULL && !ecma_is_property_lcached (prop_p));
  JERRY_ASSERT (ECMA_PROPERTY_GET_TYPE (prop_p) == ECMA_PROPERTY_TYPE_NAMEDDATA
                || ECMA_PROPERTY_GET_TYPE (prop_p) == ECMA_PROPERTY_TYPE_NAMEDACCESSOR);

#ifndef CONFIG_ECMA_LCACHE_DISABLE
  jmem_cpointer_t object_cp;

  ECMA_SET_NON_NULL_POINTER (object_cp, object_p);

  ecma_lcache_hash_entry_t *entries_p = ecma_lcache_hash_table[ecma_lcache_row_idx (object_cp, prop_name_p)];

  int32_t entry_index;
  for (entry_index = 0; entry_index < ECMA_LCACHE_HASH_ROW_LENGTH; entry_index++)
  {
    if (entries_p[entry_index].object_cp == ECMA_NULL_POINTER)
    {
      break;
    }
  }

  if (entry_index == ECMA_LCACHE_HASH_ROW_LENGTH)
  {
    /* Invalidate the last entry. */
    ecma_lcache_invalidate_entry (entries_p + ECMA_LCACHE_HASH_ROW_LENGTH - 1);

    /* Shift other entries towards the end. */
    for (uint32_t i = ECMA_LCACHE_HASH_ROW_LENGTH - 1; i > 0; i--)
    {
      entries_p[i] = entries_p[i - 1];
    }

    entry_index = 0;
  }

  ecma_lcache_hash_entry_t *entry_p = entries_p + entry_index;
  ECMA_SET_NON_NULL_POINTER (entry_p->object_cp, object_p);
  ECMA_SET_NON_NULL_POINTER (entry_p->prop_name_cp, prop_name_p);
  entry_p->prop_p = prop_p;

  ecma_set_property_lcached (entry_p->prop_p, true);
#endif /* !CONFIG_ECMA_LCACHE_DISABLE */
} /* ecma_lcache_insert */

/**
 * Lookup property in the LCache
 *
 * @return a pointer to an ecma_property_t if the lookup is successful
 *         NULL otherwise
 */
inline ecma_property_t * __attr_always_inline___
ecma_lcache_lookup (ecma_object_t *object_p, /**< object */
                    const ecma_string_t *prop_name_p) /**< property's name */
{
  JERRY_ASSERT (object_p != NULL);
  JERRY_ASSERT (prop_name_p != NULL);

#ifndef CONFIG_ECMA_LCACHE_DISABLE
  jmem_cpointer_t object_cp;
  ECMA_SET_NON_NULL_POINTER (object_cp, object_p);

  ecma_lcache_hash_entry_t *entry_p = ecma_lcache_hash_table[ecma_lcache_row_idx (object_cp, prop_name_p)];
  ecma_lcache_hash_entry_t *entry_end_p = entry_p + ECMA_LCACHE_HASH_ROW_LENGTH;

  while (entry_p < entry_end_p)
  {
    if (entry_p->object_cp == object_cp)
    {
      ecma_string_t *entry_prop_name_p = ECMA_GET_NON_NULL_POINTER (ecma_string_t,
                                                                    entry_p->prop_name_cp);

      JERRY_ASSERT ((prop_name_p->hash & ECMA_LCACHE_HASH_MASK) == (entry_prop_name_p->hash & ECMA_LCACHE_HASH_MASK));

      if (ECMA_STRING_GET_CONTAINER (prop_name_p) == ECMA_STRING_GET_CONTAINER (entry_prop_name_p)
          && prop_name_p->u.common_field == entry_prop_name_p->u.common_field)
      {
        ecma_property_t *prop_p = entry_p->prop_p;
        JERRY_ASSERT (prop_p != NULL && ecma_is_property_lcached (prop_p));

        return prop_p;
      }
      else
      {
        /* They can be equal, but generic string comparison is too costly. */
      }
    }
    entry_p++;
  }
#endif /* !CONFIG_ECMA_LCACHE_DISABLE */

  return NULL;
} /* ecma_lcache_lookup */

/**
 * Invalidate LCache entries associated with given object and property name / property
 */
void
ecma_lcache_invalidate (ecma_object_t *object_p, /**< object */
                        ecma_string_t *prop_name_p, /**< property's name */
                        ecma_property_t *prop_p) /**< property */
{
  JERRY_ASSERT (object_p != NULL);
  JERRY_ASSERT (prop_name_p != NULL);
  JERRY_ASSERT (prop_p != NULL && ecma_is_property_lcached (prop_p));
  JERRY_ASSERT (ECMA_PROPERTY_GET_TYPE (prop_p) == ECMA_PROPERTY_TYPE_NAMEDDATA
                || ECMA_PROPERTY_GET_TYPE (prop_p) == ECMA_PROPERTY_TYPE_NAMEDACCESSOR);

#ifndef CONFIG_ECMA_LCACHE_DISABLE
  jmem_cpointer_t object_cp;
  ECMA_SET_NON_NULL_POINTER (object_cp, object_p);

  ecma_lcache_hash_entry_t *entry_p = ecma_lcache_hash_table[ecma_lcache_row_idx (object_cp, prop_name_p)];

  for (uint32_t entry_index = 0; entry_index < ECMA_LCACHE_HASH_ROW_LENGTH; entry_index++)
  {
    if (entry_p->object_cp != ECMA_NULL_POINTER && entry_p->prop_p == prop_p)
    {
      JERRY_ASSERT (ECMA_GET_NON_NULL_POINTER (ecma_string_t,
                                               entry_p->prop_name_cp) == prop_name_p);
      JERRY_ASSERT (entry_p->object_cp == object_cp);

      ecma_lcache_invalidate_entry (entry_p);
      return;
    }
    entry_p++;
  }

  /* The property must be present. */
  JERRY_UNREACHABLE ();
#endif /* !CONFIG_ECMA_LCACHE_DISABLE */
} /* ecma_lcache_invalidate */

/**
 * @}
 * @}
 */