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Bug 1705777 - Factor out a function to check whether we can reuse the buffer of the leftmost leaf node r=jandem

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Differential Revision: https://phabricator.services.mozilla.com/D112392
This commit is contained in:
Jon Coppeard 2021-04-19 08:44:45 +00:00
parent 63a32b8c33
commit 75ead5d3ef
1 changed files with 59 additions and 48 deletions
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107
js/src/vm/StringType.cpp
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@ -621,6 +621,17 @@ static bool UpdateNurseryBuffersOnTransfer(js::Nursery& nursery, JSString* from,
return true;
}
static bool CanReuseLeftmostBuffer(JSRope* leftmostRope, size_t wholeLength,
bool hasTwoByteChars) {
if (!leftmostRope->leftChild()->isExtensible()) {
return false;
}
JSExtensibleString& leftmostChild = leftmostRope->leftChild()->asExtensible();
return leftmostChild.capacity() >= wholeLength &&
leftmostChild.hasTwoByteChars() == hasTwoByteChars;
}
JSLinearString* JSRope::flatten(JSContext* maybecx) {
mozilla::Maybe<AutoGeckoProfilerEntry> entry;
if (maybecx && !maybecx->isHelperThreadContext()) {
@ -711,7 +722,6 @@ JSLinearString* JSRope::flattenInternal(JSRope* root) {
const size_t wholeLength = root->length();
size_t wholeCapacity;
CharT* wholeChars;
JSString* str = root;
CharT* pos;
// JSString::setFlattenData() is used to store a tagged pointer to the parent
@ -730,62 +740,63 @@ JSLinearString* JSRope::flattenInternal(JSRope* root) {
leftmostRope = &leftmostRope->leftChild()->asRope();
}
bool reuseLeftmostBuffer = false;
bool reuseLeftmostBuffer = CanReuseLeftmostBuffer(
leftmostRope, wholeLength, std::is_same_v<CharT, char16_t>);
if (leftmostRope->leftChild()->isExtensible()) {
if (reuseLeftmostBuffer) {
JSExtensibleString& left = leftmostRope->leftChild()->asExtensible();
size_t capacity = left.capacity();
if (capacity >= wholeLength &&
left.hasTwoByteChars() == std::is_same_v<CharT, char16_t>) {
wholeChars = const_cast<CharT*>(left.nonInlineChars<CharT>(nogc));
wholeCapacity = capacity;
wholeChars = const_cast<CharT*>(left.nonInlineChars<CharT>(nogc));
wholeCapacity = capacity;
// Nursery::registerMallocedBuffer is fallible, so attempt it first before
// doing anything irreversible.
if (!UpdateNurseryBuffersOnTransfer(nursery, &left, root, wholeChars,
wholeCapacity * sizeof(CharT))) {
return nullptr;
}
leftmostRope->setNonInlineChars(wholeChars);
uint32_t left_len = left.length();
// Remove memory association for left node we're about to make into a
// dependent string.
if (left.isTenured()) {
RemoveCellMemory(&left, left.allocSize(), MemoryUse::StringContents);
}
uint32_t flags = INIT_DEPENDENT_FLAGS;
if (left.inStringToAtomCache()) {
flags |= IN_STRING_TO_ATOM_CACHE;
}
left.setLengthAndFlags(left_len, StringFlagsForCharType<CharT>(flags));
left.d.s.u3.base = (JSLinearString*)root; /* will be true on exit */
if (left.isTenured() && !root->isTenured()) {
// leftmost child -> root is a tenured -> nursery edge.
bufferIfNursery->putWholeCell(&left);
}
reuseLeftmostBuffer = true;
pos = wholeChars + left_len;
goto first_visit_node;
}
}
if (!AllocChars(root, wholeLength, &wholeChars, &wholeCapacity)) {
return nullptr;
}
if (!root->isTenured()) {
if (!nursery.registerMallocedBuffer(wholeChars,
// Nursery::registerMallocedBuffer is fallible, so attempt it first before
// doing anything irreversible.
if (!UpdateNurseryBuffersOnTransfer(nursery, &left, root, wholeChars,
wholeCapacity * sizeof(CharT))) {
js_free(wholeChars);
return nullptr;
}
leftmostRope->setNonInlineChars(wholeChars);
uint32_t left_len = left.length();
// Remove memory association for left node we're about to make into a
// dependent string.
if (left.isTenured()) {
RemoveCellMemory(&left, left.allocSize(), MemoryUse::StringContents);
}
uint32_t flags = INIT_DEPENDENT_FLAGS;
if (left.inStringToAtomCache()) {
flags |= IN_STRING_TO_ATOM_CACHE;
}
left.setLengthAndFlags(left_len, StringFlagsForCharType<CharT>(flags));
left.d.s.u3.base = (JSLinearString*)root; /* will be true on exit */
if (left.isTenured() && !root->isTenured()) {
// leftmost child -> root is a tenured -> nursery edge.
bufferIfNursery->putWholeCell(&left);
}
pos = wholeChars + left_len;
} else {
// If we can't reuse the leftmost child's buffer, allocate a new one.
if (!AllocChars(root, wholeLength, &wholeChars, &wholeCapacity)) {
return nullptr;
}
if (!root->isTenured()) {
if (!nursery.registerMallocedBuffer(wholeChars,
wholeCapacity * sizeof(CharT))) {
js_free(wholeChars);
return nullptr;
}
}
pos = wholeChars;
}
pos = wholeChars;
JSString* str = root;
first_visit_node : {
ropeBarrierDuringFlattening<usingBarrier>(str);
if (reuseLeftmostBuffer && str == leftmostRope) {