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Bug 1087643 - Don't rely on libc optimizations in ArrayBuffer.transfer (r=sfink)

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--HG--
extra : rebase_source : fac28690b020195c2e849af20d6d85ca9185d933
This commit is contained in:
Luke Wagner 2014-10-22 17:28:07 -05:00
parent be32a3e4f8
commit 8557f3dda8
1 changed files with 31 additions and 19 deletions
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50
js/src/vm/ArrayBufferObject.cpp
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@ -52,6 +52,7 @@
#include "vm/Shape-inl.h"
using mozilla::DebugOnly;
using mozilla::UniquePtr;
using namespace js;
using namespace js::gc;
@ -396,11 +397,10 @@ ArrayBufferObject::fun_transfer(JSContext *cx, unsigned argc, Value *vp)
newByteLength = size_t(i32);
}
uint8_t *newData;
UniquePtr<uint8_t, JS::FreePolicy> newData;
if (!newByteLength) {
if (!ArrayBufferObject::neuter(cx, oldBuffer, oldBuffer->contents()))
return false;
newData = nullptr;
} else {
# ifdef JS_CPU_X64
// With a 4gb mapped asm.js buffer, we can simply enable/disable access
@ -412,31 +412,43 @@ ArrayBufferObject::fun_transfer(JSContext *cx, unsigned argc, Value *vp)
// Since we try to realloc below, only allow stealing malloc'd buffers.
// If !hasMallocedContents, stealContents will malloc a copy which we
// can then realloc.
ArrayBufferObject::BufferContents stolen =
ArrayBufferObject::stealContents(cx, oldBuffer, oldBuffer->hasMallocedContents());
if (!stolen)
bool steal = oldBuffer->hasMallocedContents();
auto stolenContents = ArrayBufferObject::stealContents(cx, oldBuffer, steal);
if (!stolenContents)
return false;
if (newByteLength != oldByteLength) {
newData = cx->runtime()->pod_reallocCanGC<uint8_t>(stolen.data(), oldByteLength, newByteLength);
if (!newData) {
js_free(stolen.data());
js_ReportOutOfMemory(cx);
return false;
UniquePtr<uint8_t, JS::FreePolicy> oldData(stolenContents.data());
if (newByteLength > oldByteLength) {
// In theory, realloc+memset(0) can be optimized to avoid touching
// any pages (by using OS page mapping tricks). However, in
// practice, we don't seem to get this optimization in Firefox with
// jemalloc so calloc+memcpy are faster.
newData.reset(cx->runtime()->pod_callocCanGC<uint8_t>(newByteLength));
if (newData) {
memcpy(newData.get(), oldData.get(), oldByteLength);
} else {
// Try malloc before giving up since it might be able to succed
// by resizing oldData in-place.
newData.reset(cx->pod_realloc(oldData.get(), oldByteLength, newByteLength));
if (!newData)
return false;
oldData.release();
memset(newData.get() + oldByteLength, 0, newByteLength - oldByteLength);
}
if (newByteLength > oldByteLength)
memset(newData + oldByteLength, 0, newByteLength - oldByteLength);
} else if (newByteLength < oldByteLength) {
newData.reset(cx->pod_realloc(oldData.get(), oldByteLength, newByteLength));
if (!newData)
return false;
oldData.release();
} else {
newData = stolen.data();
newData = Move(oldData);
}
}
RootedObject newBuffer(cx, JS_NewArrayBufferWithContents(cx, newByteLength, newData));
if (!newBuffer) {
js_free(newData);
RootedObject newBuffer(cx, JS_NewArrayBufferWithContents(cx, newByteLength, newData.get()));
if (!newBuffer)
return false;
}
newData.release();
args.rval().setObject(*newBuffer);
return true;