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Bug 609440, part 1 - don't need string atomic ops (r=igor)

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This commit is contained in:
Luke Wagner 2010-11-30 18:19:43 -08:00
parent 3177a3a935
commit 992a01a5af
1 changed files with 1 additions and 34 deletions
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35
js/src/jsstr.h
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@ -317,43 +317,10 @@ struct JSString {
return e.mCapacity;
}
/*
* Methods to manipulate ATOMIZED and EXTENSIBLE flags of flat strings. It is
* safe to use these without extra locking due to the following properties:
*
* * We do not have a flatClearAtomized method, as a string remains
* atomized until the GC collects it.
*
* * A thread may call flatSetExtensible only when it is the only
* thread accessing the string until a later call to
* flatClearExtensible.
*
* * Multiple threads can call flatClearExtensible but the function actually
* clears the EXTENSIBLE flag only when the flag is set -- in which case
* only one thread can access the string (see previous property).
*
* Thus, when multiple threads access the string, JSString::flatSetAtomized
* is the only function that can update the mLengthAndFlags field of the
* string by changing the EXTENSIBLE bit from 0 to 1. We call the method only
* after the string has been hashed. When some threads in js_ValueToStringId
* see that the flag is set, it knows that the string was atomized.
*
* On the other hand, if the thread sees that the flag is unset, it could
* be seeing a stale value when another thread has just atomized the string
* and set the flag. But this can lead only to an extra call to
* js_AtomizeString. This function would find that the string was already
* hashed and return it with the atomized bit set.
*/
inline void flatSetAtomized() {
JS_ASSERT(isFlat());
JS_ASSERT(!isStatic(this));
JS_ATOMIC_SET_MASK((jsword *)&mLengthAndFlags, ATOMIZED);
}
inline void flatSetExtensible() {
JS_ASSERT(isFlat());
JS_ASSERT(!isAtomized());
mLengthAndFlags |= EXTENSIBLE;
mLengthAndFlags |= ATOMIZED;
}
inline void flatClearExtensible() {