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Tracking variables to reduce the memory consumption of scope chain. (#1819)

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Currently we keep all local variables in the scope chain as long as
a nested function is alive. These variables consume memory although
several of them are never used. This patch focuses on removing those
unused ones whose can be detected at parsing time.

JerryScript-DCO-1.0-Signed-off-by: Zoltan Herczeg zherczeg.u-szeged@partner.samsung.com
This commit is contained in:
Zoltan Herczeg
2017-05-15 09:00:57 +02:00
committed by GitHub
parent 8143a0cc10
commit f5b385ca6c
7 changed files with 168 additions and 44 deletions
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jerry-core/parser/js/js-parser.c
+124 -13
View File
@@ -32,6 +32,94 @@
* @{
*/
/**
* Copy identifiers if needed.
*/
static void
parser_copy_identifiers (parser_context_t *context_p) /**< context */
{
parser_saved_context_t *parent_p = context_p->last_context_p;
if (parent_p == NULL || parent_p->prev_context_p == NULL)
{
/* Return if this function is not a nested function. */
return;
}
if (context_p->status_flags & PARSER_NO_REG_STORE)
{
/* This flag must affect all parent functions. */
parent_p->status_flags |= PARSER_NO_REG_STORE;
return;
}
parser_list_iterator_t literal_iterator;
lexer_literal_t *literal_p;
parser_list_t parent_literal_pool;
/* Accessing the parent literal pool requires all data. */
parent_literal_pool.data = parent_p->literal_pool_data;
parent_literal_pool.page_size = context_p->literal_pool.page_size;
parent_literal_pool.item_size = context_p->literal_pool.item_size;
parent_literal_pool.item_count = context_p->literal_pool.item_count;
parser_list_iterator_init (&context_p->literal_pool, &literal_iterator);
while ((literal_p = (lexer_literal_t *) parser_list_iterator_next (&literal_iterator)))
{
if (literal_p->type != LEXER_IDENT_LITERAL || (literal_p->status_flags & LEXER_FLAG_VAR))
{
continue;
}
parser_list_iterator_t parent_literal_iterator;
parser_list_iterator_init (&parent_literal_pool, &parent_literal_iterator);
lexer_literal_t *parent_literal_p;
const uint8_t *char_p = literal_p->u.char_p;
size_t length = literal_p->prop.length;
while ((parent_literal_p = (lexer_literal_t *) parser_list_iterator_next (&parent_literal_iterator)) != NULL)
{
if (parent_literal_p->type == LEXER_IDENT_LITERAL
&& parent_literal_p->prop.length == length
&& memcmp (parent_literal_p->u.char_p, char_p, length) == 0)
{
/* This literal is known by the parent. */
parent_literal_p->status_flags |= LEXER_FLAG_NO_REG_STORE;
break;
}
}
if (parent_literal_p != NULL)
{
continue;
}
if (parent_p->literal_count >= PARSER_MAXIMUM_NUMBER_OF_LITERALS)
{
parser_raise_error (context_p, PARSER_ERR_LITERAL_LIMIT_REACHED);
}
parent_literal_p = (lexer_literal_t *) parser_list_append (context_p, &parent_literal_pool);
/* The literal data is updated at every iteration to handle out-of memory. */
parent_p->literal_pool_data = parent_literal_pool.data;
parent_literal_p->prop.length = (uint16_t) length;
parent_literal_p->type = LEXER_IDENT_LITERAL;
parent_literal_p->status_flags = (uint8_t) (literal_p->status_flags & LEXER_FLAG_SOURCE_PTR);
parent_literal_p->status_flags |= LEXER_FLAG_NO_REG_STORE | LEXER_FLAG_UNUSED_IDENT;
parent_literal_p->u.char_p = char_p;
/* The buffer ownership is passed to the parent by
* setting this flag which prevents freeing the buffer. */
literal_p->status_flags |= LEXER_FLAG_SOURCE_PTR;
parent_p->literal_count++;
}
} /* parser_copy_identifiers */
/**
* Compute real literal indicies.
*
@@ -74,6 +162,12 @@ parser_compute_indicies (parser_context_t *context_p, /**< context */
parser_list_iterator_init (&context_p->literal_pool, &literal_iterator);
while ((literal_p = (lexer_literal_t *) parser_list_iterator_next (&literal_iterator)))
{
if (literal_p->status_flags & LEXER_FLAG_UNUSED_IDENT)
{
context_p->literal_count--;
continue;
}
#ifndef PARSER_DUMP_BYTE_CODE
if (literal_p->type == LEXER_IDENT_LITERAL
|| literal_p->type == LEXER_STRING_LITERAL)
@@ -125,7 +219,7 @@ parser_compute_indicies (parser_context_t *context_p, /**< context */
{
JERRY_ASSERT (literal_p == PARSER_GET_LITERAL (0));
status_flags |= PARSER_NAMED_FUNCTION_EXP | PARSER_NO_REG_STORE | PARSER_LEXICAL_ENV_NEEDED;
status_flags |= PARSER_NAMED_FUNCTION_EXP;
context_p->status_flags = status_flags;
literal_p->status_flags |= LEXER_FLAG_NO_REG_STORE;
@@ -174,6 +268,12 @@ parser_compute_indicies (parser_context_t *context_p, /**< context */
literal_p->status_flags |= LEXER_FLAG_NO_REG_STORE;
uninitialized_var_count++;
}
if (literal_p->status_flags & LEXER_FLAG_NO_REG_STORE)
{
status_flags |= PARSER_LEXICAL_ENV_NEEDED;
context_p->status_flags = status_flags;
}
}
else
{
@@ -249,6 +349,11 @@ parser_compute_indicies (parser_context_t *context_p, /**< context */
{
uint16_t init_index;
if (literal_p->status_flags & LEXER_FLAG_UNUSED_IDENT)
{
continue;
}
if (literal_p->type != LEXER_IDENT_LITERAL)
{
if (literal_p->type == LEXER_STRING_LITERAL
@@ -349,7 +454,8 @@ parser_compute_indicies (parser_context_t *context_p, /**< context */
}
/* A CBC_INITIALIZE_VAR instruction or part of a CBC_INITIALIZE_VARS instruction. */
if (!(status_flags & PARSER_HAS_INITIALIZED_VARS))
if (!(status_flags & PARSER_HAS_INITIALIZED_VARS)
|| !(literal_p->status_flags & LEXER_FLAG_NO_REG_STORE))
{
length += 2;
if (literal_p->prop.index > literal_one_byte_limit)
@@ -438,7 +544,6 @@ parser_generate_initializers (parser_context_t *context_p, /**< context */
dst_p = parser_encode_literal (dst_p,
(uint16_t) (uninitialized_var_end - 1),
literal_one_byte_limit);
context_p->status_flags |= PARSER_LEXICAL_ENV_NEEDED;
}
if (context_p->status_flags & PARSER_HAS_INITIALIZED_VARS)
@@ -517,9 +622,12 @@ parser_generate_initializers (parser_context_t *context_p, /**< context */
|| literal_p->type == LEXER_STRING_LITERAL)
{
#ifdef PARSER_DUMP_BYTE_CODE
jmem_cpointer_t lit_cp = ecma_find_or_create_literal_string (literal_p->u.char_p,
literal_p->prop.length);
literal_pool_p[literal_p->prop.index] = lit_cp;
if (!(literal_p->status_flags & LEXER_FLAG_UNUSED_IDENT))
{
jmem_cpointer_t lit_cp = ecma_find_or_create_literal_string (literal_p->u.char_p,
literal_p->prop.length);
literal_pool_p[literal_p->prop.index] = lit_cp;
}
if (!context_p->is_show_opcodes
&& !(literal_p->status_flags & LEXER_FLAG_SOURCE_PTR))
@@ -527,7 +635,10 @@ parser_generate_initializers (parser_context_t *context_p, /**< context */
jmem_heap_free_block ((void *) literal_p->u.char_p, literal_p->prop.length);
}
#else /* !PARSER_DUMP_BYTE_CODE */
literal_pool_p[literal_p->prop.index] = literal_p->u.value;
if (!(literal_p->status_flags & LEXER_FLAG_UNUSED_IDENT))
{
literal_pool_p[literal_p->prop.index] = literal_p->u.value;
}
#endif /* PARSER_DUMP_BYTE_CODE */
}
else if ((literal_p->type == LEXER_FUNCTION_LITERAL)
@@ -555,8 +666,6 @@ parser_generate_initializers (parser_context_t *context_p, /**< context */
JERRY_ASSERT (literal_p->type == LEXER_IDENT_LITERAL);
context_p->status_flags |= PARSER_LEXICAL_ENV_NEEDED;
if (literal_p->status_flags & LEXER_FLAG_FUNCTION_NAME)
{
init_index = const_literal_end;
@@ -869,7 +978,6 @@ parse_print_literal (ecma_compiled_code_t *compiled_code_p, /**< compiled code *
if (literal_p == NULL)
{
if (literal_index == const_literal_end)
{
JERRY_DEBUG_MSG (" idx:%d(self)->function", literal_index);
@@ -882,7 +990,8 @@ parse_print_literal (ecma_compiled_code_t *compiled_code_p, /**< compiled code *
}
if (literal_p->prop.index == literal_index
&& literal_p->type != LEXER_UNUSED_LITERAL)
&& literal_p->type != LEXER_UNUSED_LITERAL
&& !(literal_p->status_flags & LEXER_FLAG_UNUSED_IDENT))
{
JERRY_DEBUG_MSG (" idx:%d", literal_index);
@@ -1293,8 +1402,7 @@ parser_post_processing (parser_context_t *context_p) /**< context */
}
#endif /* JERRY_DEBUGGER */
last_page_p = context_p->byte_code.last_p;
last_position = context_p->byte_code.last_position;
parser_copy_identifiers (context_p);
initializers_length = parser_compute_indicies (context_p,
&ident_end,
@@ -1312,6 +1420,9 @@ parser_post_processing (parser_context_t *context_p) /**< context */
literal_one_byte_limit = CBC_LOWER_SEVEN_BIT_MASK;
}
last_page_p = context_p->byte_code.last_p;
last_position = context_p->byte_code.last_position;
if (last_position >= PARSER_CBC_STREAM_PAGE_SIZE)
{
last_page_p = NULL;