Changeset 43048 in webkit for trunk/JavaScriptCore/runtime/UString.cpp

Timestamp:

Apr 30, 2009, 2:15:36 AM (16 years ago)

Author:

[email protected]

Message:

2009-04-30 Maciej Stachowiak <​[email protected]>

Reviewed by Alexey Proskuryakov.

• speed up string concatenation by reorganizing some simple cases

0.7% SunSpider speedup

• runtime/UString.cpp: (JSC::concatenate): Put fast case for appending a single character before the empty string special cases; streamline code a bit to delay computing values that are not needed in the fast path.

File:

• trunk/JavaScriptCore/runtime/UString.cpp (modified) (2 diffs)

trunk/JavaScriptCore/runtime/UString.cpp

@@ -619 +619 @@
 
     int aSize = a->size();
+    int bSize = b->size();
     int aOffset = a->offset;
-    int bSize = b->size();
-    int bOffset = b->offset;
-    int length = aSize + bSize;
 
     // possible cases:
+
+    UString::BaseString* aBase = a->baseString();
+    if (bSize == 1 && aOffset + aSize == aBase->usedCapacity && aOffset + aSize < aBase->capacity) {
+        // b is a single character (common fast case)
+        ++aBase->usedCapacity;
+        a->data()[aSize] = b->data()[0];
+        return UString::Rep::create(a, 0, aSize + 1);
+    }
 
     // a is empty
@@ -633 +639 @@
         return a;
 
-    UString::BaseString* aBase = a->baseString();
-    if (bSize == 1 && aOffset + aSize == aBase->usedCapacity && aOffset + length <= aBase->capacity) {
-        // b is a single character (common fast case)
-        aBase->usedCapacity = aOffset + length;
-        a->data()[aSize] = b->data()[0];
-        return UString::Rep::create(a, 0, length);
-    }
+    int bOffset = b->offset;
+    int length = aSize + bSize;
 
     UString::BaseString* bBase = b->baseString();