xref: /third_party/jerryscript/jerry-core/vm/vm-stack.c

/* Copyright JS Foundation and other contributors, http://js.foundation
 *
 * 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-alloc.h"
#include "ecma-gc.h"
#include "ecma-helpers.h"
#include "vm-defines.h"
#include "vm-stack.h"
#include "ecma-iterator-object.h"

/** \addtogroup vm Virtual machine
 * @{
 *
 * \addtogroup stack VM stack
 * @{
 */

JERRY_STATIC_ASSERT (PARSER_WITH_CONTEXT_STACK_ALLOCATION == PARSER_BLOCK_CONTEXT_STACK_ALLOCATION,
                     parser_with_context_stack_allocation_must_be_equal_to_parser_block_context_stack_allocation);

/**
 * Abort (finalize) the current stack context, and remove it.
 *
 * @return new stack top
 */
ecma_value_t *
vm_stack_context_abort (vm_frame_ctx_t *frame_ctx_p, /**< frame context */
                        ecma_value_t *vm_stack_top_p) /**< current stack top */
{
  ecma_value_t context_info = vm_stack_top_p[-1];

  if (context_info & VM_CONTEXT_HAS_LEX_ENV)
  {
    ecma_object_t *lex_env_p = frame_ctx_p->lex_env_p;
    JERRY_ASSERT (lex_env_p->u2.outer_reference_cp != JMEM_CP_NULL);
    frame_ctx_p->lex_env_p = ECMA_GET_NON_NULL_POINTER (ecma_object_t, lex_env_p->u2.outer_reference_cp);
    ecma_deref_object (lex_env_p);
  }

  switch (VM_GET_CONTEXT_TYPE (context_info))
  {
    case VM_CONTEXT_FINALLY_THROW:
    case VM_CONTEXT_FINALLY_RETURN:
    {
      ecma_free_value (vm_stack_top_p[-2]);
      /* FALLTHRU */
    }
    case VM_CONTEXT_FINALLY_JUMP:
    case VM_CONTEXT_TRY:
    case VM_CONTEXT_CATCH:
    {
      VM_MINUS_EQUAL_U16 (frame_ctx_p->context_depth, PARSER_TRY_CONTEXT_STACK_ALLOCATION);
      vm_stack_top_p -= PARSER_TRY_CONTEXT_STACK_ALLOCATION;
      break;
    }
#if ENABLED (JERRY_ES2015)
    case VM_CONTEXT_BLOCK:
#endif /* ENABLED (JERRY_ES2015) */
    case VM_CONTEXT_WITH:
    {
      VM_MINUS_EQUAL_U16 (frame_ctx_p->context_depth, PARSER_WITH_CONTEXT_STACK_ALLOCATION);
      vm_stack_top_p -= PARSER_WITH_CONTEXT_STACK_ALLOCATION;
      break;
    }
#if ENABLED (JERRY_ES2015)
    case VM_CONTEXT_FOR_OF:
    {
      ecma_value_t iterator = vm_stack_top_p[-3];

      if (context_info & VM_CONTEXT_CLOSE_ITERATOR)
      {
        ecma_op_iterator_close (iterator);
      }
      ecma_free_value (iterator);

      ecma_free_value (vm_stack_top_p[-2]);
      VM_MINUS_EQUAL_U16 (frame_ctx_p->context_depth, PARSER_FOR_OF_CONTEXT_STACK_ALLOCATION);
      vm_stack_top_p -= PARSER_FOR_OF_CONTEXT_STACK_ALLOCATION;
      break;
    }
#endif /* ENABLED (JERRY_ES2015) */
    default:
    {
      JERRY_ASSERT (VM_GET_CONTEXT_TYPE (vm_stack_top_p[-1]) == VM_CONTEXT_FOR_IN);

      ecma_collection_t *collection_p;
      collection_p = ECMA_GET_INTERNAL_VALUE_POINTER (ecma_collection_t, vm_stack_top_p[-2]);

      ecma_value_t *buffer_p = collection_p->buffer_p;

      for (uint32_t index = vm_stack_top_p[-3]; index < collection_p->item_count; index++)
      {
        ecma_free_value (buffer_p[index]);
      }

      ecma_collection_destroy (collection_p);

      ecma_free_value (vm_stack_top_p[-4]);

      VM_MINUS_EQUAL_U16 (frame_ctx_p->context_depth, PARSER_FOR_IN_CONTEXT_STACK_ALLOCATION);
      vm_stack_top_p -= PARSER_FOR_IN_CONTEXT_STACK_ALLOCATION;
      break;
    }
  }

  return vm_stack_top_p;
} /* vm_stack_context_abort */

/**
 * Decode branch offset.
 *
 * @return branch offset
 */
static uint32_t
vm_decode_branch_offset (const uint8_t *branch_offset_p, /**< start offset of byte code */
                         uint32_t length) /**< length of the branch */
{
  uint32_t branch_offset = *branch_offset_p;

  JERRY_ASSERT (length >= 1 && length <= 3);

  switch (length)
  {
    case 3:
    {
      branch_offset <<= 8;
      branch_offset |= *(++branch_offset_p);
      /* FALLTHRU */
    }
    case 2:
    {
      branch_offset <<= 8;
      branch_offset |= *(++branch_offset_p);
      break;
    }
  }

  return branch_offset;
} /* vm_decode_branch_offset */

/**
 * Find a finally up to the end position.
 *
 * @return true - if 'finally' found,
 *         false - otherwise
 */
bool
vm_stack_find_finally (vm_frame_ctx_t *frame_ctx_p, /**< frame context */
                       ecma_value_t **vm_stack_top_ref_p, /**< current stack top */
                       vm_stack_context_type_t finally_type, /**< searching this finally */
                       uint32_t search_limit) /**< search up-to this byte code */
{
  ecma_value_t *vm_stack_top_p = *vm_stack_top_ref_p;

  JERRY_ASSERT (finally_type <= VM_CONTEXT_FINALLY_RETURN);

  if (finally_type != VM_CONTEXT_FINALLY_JUMP)
  {
    search_limit = 0xffffffffu;
  }

  while (frame_ctx_p->context_depth > 0)
  {
    vm_stack_context_type_t context_type;
    uint32_t context_end = VM_GET_CONTEXT_END (vm_stack_top_p[-1]);

    if (search_limit < context_end)
    {
      *vm_stack_top_ref_p = vm_stack_top_p;
      return false;
    }

    context_type = VM_GET_CONTEXT_TYPE (vm_stack_top_p[-1]);
    if (context_type == VM_CONTEXT_TRY || context_type == VM_CONTEXT_CATCH)
    {
      const uint8_t *byte_code_p;
      uint32_t branch_offset_length;
      uint32_t branch_offset;

      if (search_limit == context_end)
      {
        *vm_stack_top_ref_p = vm_stack_top_p;
        return false;
      }

#if ENABLED (JERRY_ES2015)
      if (vm_stack_top_p[-1] & VM_CONTEXT_HAS_LEX_ENV)
      {
        ecma_object_t *lex_env_p = frame_ctx_p->lex_env_p;
        JERRY_ASSERT (lex_env_p->u2.outer_reference_cp != JMEM_CP_NULL);
        frame_ctx_p->lex_env_p = ECMA_GET_NON_NULL_POINTER (ecma_object_t, lex_env_p->u2.outer_reference_cp);
        ecma_deref_object (lex_env_p);
      }
#endif /* ENABLED (JERRY_ES2015) */

      byte_code_p = frame_ctx_p->byte_code_start_p + context_end;

      if (context_type == VM_CONTEXT_TRY)
      {
        JERRY_ASSERT (byte_code_p[0] == CBC_EXT_OPCODE);

        if (byte_code_p[1] >= CBC_EXT_CATCH
            && byte_code_p[1] <= CBC_EXT_CATCH_3)
        {
          branch_offset_length = CBC_BRANCH_OFFSET_LENGTH (byte_code_p[1]);
          branch_offset = vm_decode_branch_offset (byte_code_p + 2,
                                                   branch_offset_length);

          if (finally_type == VM_CONTEXT_FINALLY_THROW)
          {
            branch_offset += (uint32_t) (byte_code_p - frame_ctx_p->byte_code_start_p);

            vm_stack_top_p[-1] = VM_CREATE_CONTEXT (VM_CONTEXT_CATCH, branch_offset);

            byte_code_p += 2 + branch_offset_length;
            frame_ctx_p->byte_code_p = byte_code_p;

            *vm_stack_top_ref_p = vm_stack_top_p;
            return true;
          }

          byte_code_p += branch_offset;

          if (*byte_code_p == CBC_CONTEXT_END)
          {
            VM_MINUS_EQUAL_U16 (frame_ctx_p->context_depth, PARSER_TRY_CONTEXT_STACK_ALLOCATION);
            vm_stack_top_p -= PARSER_TRY_CONTEXT_STACK_ALLOCATION;
            continue;
          }
        }
      }
      else
      {
#if !ENABLED (JERRY_ES2015)
        if (vm_stack_top_p[-1] & VM_CONTEXT_HAS_LEX_ENV)
        {
          ecma_object_t *lex_env_p = frame_ctx_p->lex_env_p;
          JERRY_ASSERT (lex_env_p->u2.outer_reference_cp != JMEM_CP_NULL);
          frame_ctx_p->lex_env_p = ECMA_GET_NON_NULL_POINTER (ecma_object_t, lex_env_p->u2.outer_reference_cp);
          ecma_deref_object (lex_env_p);
        }
#endif /* !ENABLED (JERRY_ES2015) */

        if (byte_code_p[0] == CBC_CONTEXT_END)
        {
          VM_MINUS_EQUAL_U16 (frame_ctx_p->context_depth, PARSER_TRY_CONTEXT_STACK_ALLOCATION);
          vm_stack_top_p -= PARSER_TRY_CONTEXT_STACK_ALLOCATION;
          continue;
        }
      }

      JERRY_ASSERT (byte_code_p[0] == CBC_EXT_OPCODE);
      JERRY_ASSERT (byte_code_p[1] >= CBC_EXT_FINALLY
                    && byte_code_p[1] <= CBC_EXT_FINALLY_3);

      branch_offset_length = CBC_BRANCH_OFFSET_LENGTH (byte_code_p[1]);
      branch_offset = vm_decode_branch_offset (byte_code_p + 2,
                                               branch_offset_length);

      branch_offset += (uint32_t) (byte_code_p - frame_ctx_p->byte_code_start_p);

      vm_stack_top_p[-1] = VM_CREATE_CONTEXT ((uint32_t) finally_type, branch_offset);

      byte_code_p += 2 + branch_offset_length;
      frame_ctx_p->byte_code_p = byte_code_p;

      *vm_stack_top_ref_p = vm_stack_top_p;
      return true;
    }

    vm_stack_top_p = vm_stack_context_abort (frame_ctx_p, vm_stack_top_p);
  }

  *vm_stack_top_ref_p = vm_stack_top_p;
  return false;
} /* vm_stack_find_finally */

#if ENABLED (JERRY_ES2015)

/**
 * Get the offsets of ecma values from the specified item of a context.
 *
 * @return array of offsets, last item represents the size of the context item
 */
uint32_t
vm_get_context_value_offsets (ecma_value_t *context_item_p) /**< any item of a context */
{
  switch (VM_GET_CONTEXT_TYPE (context_item_p[-1]))
  {
    case VM_CONTEXT_FINALLY_THROW:
    case VM_CONTEXT_FINALLY_RETURN:
    {
      return (2 << (VM_CONTEXT_OFFSET_SHIFT)) | PARSER_TRY_CONTEXT_STACK_ALLOCATION;
    }
    case VM_CONTEXT_FINALLY_JUMP:
    case VM_CONTEXT_TRY:
    case VM_CONTEXT_CATCH:
    {
      return PARSER_TRY_CONTEXT_STACK_ALLOCATION;
    }
#if ENABLED (JERRY_ES2015)
    case VM_CONTEXT_BLOCK:
#endif /* ENABLED (JERRY_ES2015) */
    case VM_CONTEXT_WITH:
    {
      return PARSER_WITH_CONTEXT_STACK_ALLOCATION;
    }
#if ENABLED (JERRY_ES2015)
    case VM_CONTEXT_FOR_OF:
    {
      return ((3 << (VM_CONTEXT_OFFSET_SHIFT * 2))
              | (2 << (VM_CONTEXT_OFFSET_SHIFT))
              | PARSER_FOR_OF_CONTEXT_STACK_ALLOCATION);
    }
#endif /* ENABLED (JERRY_ES2015) */
    default:
    {
      return (4 << (VM_CONTEXT_OFFSET_SHIFT)) | PARSER_FOR_IN_CONTEXT_STACK_ALLOCATION;
    }
  }
} /* vm_get_context_value_offsets */

/**
 * Ref / deref lexical environments in the chain using the current context.
 */
void
vm_ref_lex_env_chain (ecma_object_t *lex_env_p, /**< top of lexical environment */
                      uint16_t context_depth, /**< depth of function context */
                      ecma_value_t *context_end_p, /**< end of function context */
                      bool do_ref) /**< ref or deref lexical environments */
{
  ecma_value_t *context_top_p = context_end_p + context_depth;
  JERRY_ASSERT (context_top_p > context_end_p);

  do
  {
    if (context_top_p[-1] & VM_CONTEXT_HAS_LEX_ENV)
    {
      JERRY_ASSERT (lex_env_p->u2.outer_reference_cp != JMEM_CP_NULL);
      ecma_object_t *next_lex_env_p = ECMA_GET_NON_NULL_POINTER (ecma_object_t, lex_env_p->u2.outer_reference_cp);

      if (do_ref)
      {
        ecma_ref_object (lex_env_p);
      }
      else
      {
        ecma_deref_object (lex_env_p);
      }

      lex_env_p = next_lex_env_p;
    }

    uint32_t offsets = vm_get_context_value_offsets (context_top_p);

    while (VM_CONTEXT_HAS_NEXT_OFFSET (offsets))
    {
      int32_t offset = VM_CONTEXT_GET_NEXT_OFFSET (offsets);

      if (do_ref)
      {
        ecma_ref_if_object (context_top_p[offset]);
      }
      else
      {
        ecma_deref_if_object (context_top_p[offset]);
      }

      offsets >>= VM_CONTEXT_OFFSET_SHIFT;
    }

    JERRY_ASSERT (context_top_p >= context_end_p + offsets);
    context_top_p -= offsets;
  }
  while (context_top_p > context_end_p);
} /* vm_ref_lex_env_chain */

#endif /* ENABLED (JERRY_ES2015) */

/**
 * @}
 * @}
 */