Changeset 44984 in webkit for trunk/JavaScriptCore

Timestamp:

Jun 23, 2009, 2:14:40 AM (16 years ago)

Author:

[email protected]

Message:

Fix stupid performance problem in the LiteralParser

Reviewed by Alexey Proskuryakov.

The LiteralParser was making a new UString in order to use
toDouble, however UString's toDouble allows a much wider range
of numberic strings than the LiteralParser accepts, and requires
an additional heap allocation or two for the construciton of the
UString. To rectify this we just call WTF::dtoa directly using
a stack allocated buffer to hold the validated numeric literal.

Location:

trunk/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• runtime/LiteralParser.cpp (modified) (3 diffs)
• runtime/LiteralParser.h (modified) (1 diff)

trunk/JavaScriptCore/ChangeLog

@@ +1 @@
+2009-06-23  Oliver Hunt  <[email protected]>
+
+        Reviewed by Alexey Proskuryakov.
+
+        Fix stupid performance problem in the LiteralParser
+
+        The LiteralParser was making a new UString in order to use
+        toDouble, however UString's toDouble allows a much wider range
+        of numberic strings than the LiteralParser accepts, and requires
+        an additional heap allocation or two for the construciton of the
+        UString.  To rectify this we just call WTF::dtoa directly using
+        a stack allocated buffer to hold the validated numeric literal.
+
+        * runtime/LiteralParser.cpp:
+        (JSC::LiteralParser::Lexer::lexNumber):
+        (JSC::LiteralParser::parse):
+        * runtime/LiteralParser.h:
+
 2009-06-22  Oliver Hunt  <[email protected]>
 

trunk/JavaScriptCore/runtime/LiteralParser.cpp

@@ -31 +31 @@
 #include "Lexer.h"
 #include <wtf/ASCIICType.h>
+#include <wtf/dtoa.h>
 
 namespace JSC {
@@ -264 +265 @@
     token.type = TokNumber;
     token.end = m_ptr;
+    Vector<char, 64> buffer(token.end - token.start + 1);
+    int i;
+    for (i = 0; i < token.end - token.start; i++) {
+        ASSERT(static_cast<char>(token.start[i]) == token.start[i]);
+        buffer[i] = static_cast<char>(token.start[i]);
+    }
+    buffer[i] = 0;
+    char* end;
+    token.numberToken = WTF::strtod(buffer.data(), &end);
+    ASSERT(buffer.data() + (token.end - token.start) == end);
     return TokNumber;
 }
@@ -377 +388 @@
                         Lexer::LiteralParserToken numberToken = m_lexer.currentToken();
                         m_lexer.next();
-                        lastValue = jsNumber(m_exec, UString(numberToken.start, numberToken.end - numberToken.start).toDouble());
+                        lastValue = jsNumber(m_exec, numberToken.numberToken);
                         break;
                     }

trunk/JavaScriptCore/runtime/LiteralParser.h

@@ -68 +68 @@
                 const UChar* end;
                 UString stringToken;
+                double numberToken;
             };
             Lexer(const UString& s, ParserMode mode)