Improve line info construction (#4718)

- Simplify small encoding
- Better line info for some corner cases

JerryScript-DCO-1.0-Signed-off-by: Zoltan Herczeg zherczeg.u-szeged@partner.samsung.com

jerry-core/ecma/base/ecma-line-info.c

@@ -62,35 +62,23 @@ static uint32_t
 ecma_line_info_decode_small (uint8_t **buffer_p) /**< [in/out] target buffer */
 {
   uint8_t *source_p = *buffer_p;
-
   uint32_t type = source_p[0];
 
+  *buffer_p = source_p + 1;
+
   if (type < ECMA_LINE_INFO_ENCODE_TWO_BYTE_MIN)
   {
-    *buffer_p = source_p + 1;
     return type;
   }
 
-  uint32_t value = source_p[1];
-
   if (type == ECMA_LINE_INFO_ENCODE_TWO_BYTE)
   {
     *buffer_p = source_p + 2;
-    return (uint32_t) (value + ECMA_LINE_INFO_ENCODE_TWO_BYTE_MIN);
+    return ((uint32_t) source_p[1]) + ECMA_LINE_INFO_ENCODE_TWO_BYTE_MIN;
   }
 
-  value |= ((uint32_t) source_p[2]) << 8;
-
-  if (type == ECMA_LINE_INFO_ENCODE_THREE_BYTE)
-  {
-    *buffer_p = source_p + 3;
-    return (uint32_t) (value + ECMA_LINE_INFO_ENCODE_THREE_BYTE_MIN);
-  }
-
-  JERRY_ASSERT (type == ECMA_LINE_INFO_ENCODE_FIVE_BYTE);
-
-  *buffer_p = source_p + 5;
-  return value | (((uint32_t) source_p[3]) << 8) | (((uint32_t) source_p[4]) << 8);
+  JERRY_ASSERT (type == ECMA_LINE_INFO_ENCODE_VLQ);
+  return ecma_line_info_decode_vlq (buffer_p) + ECMA_LINE_INFO_ENCODE_VLQ_MIN;
 } /* ecma_line_info_decode_small */
 
 /**

jerry-core/ecma/base/ecma-line-info.h

@@ -45,7 +45,7 @@
 /**
  * A default value for columns after a line update.
  */
-#define ECMA_LINE_INFO_COLUMN_DEFAULT 126
+#define ECMA_LINE_INFO_COLUMN_DEFAULT 127
 
 /**
  * Vlq encoding: flag which is set for all bytes except the last one.
@@ -65,27 +65,22 @@
 /**
  * Small encoding: a value which represents a two byte long number.
  */
-#define ECMA_LINE_INFO_ENCODE_TWO_BYTE (UINT8_MAX - 2)
+#define ECMA_LINE_INFO_ENCODE_TWO_BYTE (UINT8_MAX - 1)
 
 /**
  * Small encoding: minimum value of an encoded two byte long number.
  */
-#define ECMA_LINE_INFO_ENCODE_TWO_BYTE_MIN (UINT8_MAX - 2)
+#define ECMA_LINE_INFO_ENCODE_TWO_BYTE_MIN (UINT8_MAX - 1)
 
 /**
  * Small encoding: a value which represents a three byte long number.
  */
-#define ECMA_LINE_INFO_ENCODE_THREE_BYTE (UINT8_MAX - 1)
+#define ECMA_LINE_INFO_ENCODE_VLQ UINT8_MAX
 
 /**
  * Small encoding: minimum value of an encoded three byte long number.
  */
-#define ECMA_LINE_INFO_ENCODE_THREE_BYTE_MIN (ECMA_LINE_INFO_ENCODE_TWO_BYTE_MIN + UINT8_MAX + 1)
-
-/**
- * Small encoding: a value which represents a five byte long number.
- */
-#define ECMA_LINE_INFO_ENCODE_FIVE_BYTE UINT8_MAX
+#define ECMA_LINE_INFO_ENCODE_VLQ_MIN (ECMA_LINE_INFO_ENCODE_TWO_BYTE_MIN + UINT8_MAX + 1)
 
 /**
  * Maximum number of line/column entries stored in a stream.

jerry-core/parser/js/js-parser-line-info-create.c

@@ -38,8 +38,9 @@
  *    The format is big endian.
  *
  * Small:
- *    First byte can encode signed values between 127 and -125 in 1 byte.
- *    Large values requires more bytes than vlq.
+ *    One byte can encode signed values between 127 and -126.
+ *    Two byte can encode signed values between 319 and -318.
+ *    Large values are encoded with vlq with a prefix byte.
  *
  * The line-info data structure is a sequence of chunks:
  *
@@ -87,7 +88,7 @@
 /**
  * Maximum number of bytes requires to encode a number.
  */
-#define PARSER_LINE_INFO_BUFFER_MAX_SIZE 5
+#define PARSER_LINE_INFO_BUFFER_MAX_SIZE 6
 
 /**
  * Stream generation ends after this size is reached,
@@ -160,41 +161,21 @@ static uint32_t
 parser_line_info_encode_small (uint8_t *buffer_p, /**< target buffer */
                                uint32_t value) /**< encoded value */
 {
-  if (value < ECMA_LINE_INFO_ENCODE_TWO_BYTE_MIN)
+  if (JERRY_LIKELY (value < ECMA_LINE_INFO_ENCODE_TWO_BYTE_MIN))
   {
     buffer_p[0] = (uint8_t) value;
     return 1;
   }
 
-  uint32_t length;
-
-  if (JERRY_LIKELY (value < ECMA_LINE_INFO_ENCODE_THREE_BYTE_MIN))
+  if (JERRY_LIKELY (value < ECMA_LINE_INFO_ENCODE_VLQ_MIN))
   {
-    value -= ECMA_LINE_INFO_ENCODE_TWO_BYTE_MIN;
     buffer_p[0] = ECMA_LINE_INFO_ENCODE_TWO_BYTE;
-    length = 2;
-  }
-  else
-  {
-    if (value <= (ECMA_LINE_INFO_ENCODE_THREE_BYTE_MIN + UINT16_MAX))
-    {
-      value -= ECMA_LINE_INFO_ENCODE_THREE_BYTE_MIN;
-      buffer_p[0] = ECMA_LINE_INFO_ENCODE_THREE_BYTE;
-      length = 3;
-    }
-    else
-    {
-      buffer_p[0] = ECMA_LINE_INFO_ENCODE_FIVE_BYTE;
-      buffer_p[3] = (uint8_t) (value >> 16);
-      buffer_p[4] = (uint8_t) (value >> 24);
-      length = 5;
-    }
-
-    buffer_p[2] = (uint8_t) (value >> 8);
+    buffer_p[1] = (uint8_t) (value - ECMA_LINE_INFO_ENCODE_TWO_BYTE_MIN);
+    return 2;
   }
 
-  buffer_p[1] = (uint8_t) value;
-  return length;
+  *buffer_p++ = ECMA_LINE_INFO_ENCODE_VLQ;
+  return parser_line_info_encode_vlq (buffer_p, value - ECMA_LINE_INFO_ENCODE_VLQ_MIN) + 1;
 } /* parser_line_info_encode_small */
 
 /**

jerry-core/parser/js/js-parser-statm.c

@@ -3339,6 +3339,13 @@ parser_parse_statements (parser_context_t *context_p) /**< context */
       {
         if (context_p->status_flags & PARSER_IS_CLOSURE)
         {
+#if JERRY_LINE_INFO
+          if (context_p->line_info.first_page_p == NULL)
+          {
+            parser_line_info_append (context_p, context_p->token.line, context_p->token.column);
+          }
+#endif /* JERRY_LINE_INFO */
+
           parser_stack_pop_uint8 (context_p);
           context_p->last_statement.current_p = NULL;
           /* There is no lexer_next_token here, since the
@@ -3501,6 +3508,13 @@ consume_last_statement:
   {
     parser_raise_error (context_p, PARSER_ERR_STATEMENT_EXPECTED);
   }
+
+#if JERRY_LINE_INFO
+  if (context_p->line_info.first_page_p == NULL)
+  {
+    parser_line_info_append (context_p, context_p->token.line, context_p->token.column);
+  }
+#endif /* JERRY_LINE_INFO */
 } /* parser_parse_statements */
 
 /**

jerry-core/parser/js/js-parser.c

@@ -650,10 +650,7 @@ parser_post_processing (parser_context_t *context_p) /**< context */
 #endif /* JERRY_ESNEXT */
 
 #if JERRY_LINE_INFO
-  if (context_p->line_info.first_page_p == NULL)
-  {
-    parser_line_info_append (context_p, context_p->token.line, context_p->token.column);
-  }
+  JERRY_ASSERT (context_p->line_info.first_page_p != NULL);
 #endif /* JERRY_LINE_INFO */
 
   JERRY_ASSERT (context_p->stack_depth == 0);
@@ -2484,6 +2481,10 @@ parser_parse_arrow_function (parser_context_t *context_p, /**< context */
       parser_raise_error (context_p, PARSER_ERR_NON_STRICT_ARG_DEFINITION);
     }
 
+#if JERRY_LINE_INFO
+    parser_line_info_append (context_p, context_p->token.line, context_p->token.column);
+#endif /* JERRY_LINE_INFO */
+
     parser_parse_expression (context_p, PARSE_EXPR_NO_COMMA);
 
     if (context_p->last_cbc_opcode == CBC_PUSH_LITERAL)
@@ -2600,12 +2601,13 @@ parser_parse_class_fields (parser_context_t *context_p) /**< context */
         scanner_seek (context_p);
       }
 
+      context_p->source_end_p = range.source_end_p;
+      lexer_next_token (context_p);
+
 #if JERRY_LINE_INFO
       parser_line_info_append (context_p, context_p->token.line, context_p->token.column);
 #endif /* JERRY_LINE_INFO */
 
-      context_p->source_end_p = range.source_end_p;
-      lexer_next_token (context_p);
       parser_parse_expression (context_p, PARSE_EXPR_NO_COMMA);
 
       if (context_p->token.type != LEXER_EOS)
@@ -2657,6 +2659,13 @@ parser_parse_class_fields (parser_context_t *context_p) /**< context */
   context_p->source_end_p = source_end_p;
   scanner_set_location (context_p, &end_location);
 
+#if JERRY_LINE_INFO
+  if (context_p->line_info.first_page_p == NULL)
+  {
+    parser_line_info_append (context_p, context_p->token.line, context_p->token.column);
+  }
+#endif /* JERRY_LINE_INFO */
+
   compiled_code_p = parser_post_processing (context_p);
 
 #if JERRY_PARSER_DUMP_BYTE_CODE

tests/jerry/eval.js

@@ -159,3 +159,13 @@ function f7() {
   eval("assert(x()() === 5); function y() { return 5 } assert(x()() === 5)");
 }
 f7()
+
+eval(" ");
+eval("(function () {})")
+
+try {
+  /* Only fails in ES5.1 */
+  eval("()=>0")
+} catch (e) {
+  assert(e instanceof SyntaxError)
+}

tests/unit-core/test-backtrace.c

@@ -159,14 +159,14 @@ class_backtrace_callback (jerry_backtrace_frame_t *frame_p, /* frame information
   {
     TEST_ASSERT (jerry_backtrace_is_strict (frame_p));
     TEST_ASSERT (location_p->line == 3);
-    TEST_ASSERT (location_p->column == 12);
+    TEST_ASSERT (location_p->column == 14);
     return false;
   }
 
   TEST_ASSERT (frame_index == 2);
   TEST_ASSERT (jerry_backtrace_is_strict (frame_p));
   TEST_ASSERT (location_p->line == 2);
-  TEST_ASSERT (location_p->column == 5);
+  TEST_ASSERT (location_p->column == 7);
   return false;
 } /* class_backtrace_callback */