Backlog of Qt and QtWebKit problems

Qt problems

Description	Branch	Landed in
ARM optimized qdrawhelper is only enabled for RCVT (symbian) . The needs to be transferred to gcc inline assembly. This will optimize memfill, Source, SourceOver and some blend functions.
ARMv6 should be auto detected. Currently arm/armv6 can be passed as -embedded options. The benefit of ARMv6 in src/corelib is the use of atomic load and exchange, instead of the old "swap" extension. __ARCH_ARM_6__ should be used to detect it.
Enabled pld (preload) in qdrawhelper for ARMv5te and upwards
QImageReader deserves some optimatations. E.g. decode to the QImage provided to the decoder, do not parse every gif when trying to determine the size.	​image-changes
Cut down on usage of QImage::scanLine inside Qt. This was already done in the GIF and PNG decoder.	​image-changes
Make QGifHandler::imageCount scan through the images. This can give a 5% speedup in the image_cycling reduction.
Make picking a QImageIOHandler in QImageReader faster. Currently even the TIFF plugin is asked to handle images.
Bring zero-copy to QIODevice... big one. That is good for networking and image decoding.
Changes to QHttpNetworkReply to reduce memory reallocations. Reserve some bytes instead of doing QByteArray::append all them time.
Changes to QNetworkReply to remove quadratic runtime in QNetworkReplyHandler and latency fixes
Cut down on the usage of QUrl::toEncoded as it shows up in the profile of starting jobs.
QBENCHMARK results are hard to analyze and compare. We need a single and simple way to say if something is faster or slower. Be a bit like sunpsider, do the same math as well, mention slowest and fastest run.

QtWebKit problems

• Loading of ​http://en.wikipedia.org/wiki/Maxwell_equations is triggering bad "scheduling". The loading_standalone test has been extracted but is not able to highlight the problem. This is a Qt and QtWebKit issue, it must be understood first.

• TCmalloc needs to be tested. Does it make anything faster/slower? How to test memory fragmentation.

• The fuzz testing will make QtWebKit go in infinite loops and stop working. This situation needs to be analyzed as this can be a serve reliabality problem.

• Research a better QImage -> QPixmap migration strategy. Currently we convert every QImage to a QPixmap and this is bad for times where we need to draw a scaled version of the image or will only draw this image once. The bug report is ​here

• Loading speed ​regression

• Loading bug/API bug on loading amazon in QtEmbedded Linux. ​#30301

• Go through the Palm changes and consider adopting them. Currently candidates are: Use stack/class memory in CSSParser, use JDCT_Fast for Jpeg decoding (to be achieved with QImageReader to set quality to 49), changes to Cached* to throw away encoded data more early. Palm avoids floating point operation on premultiplied alpha in setRGBA.

• Using QImageReader::setQuality(49) will use JDCT_IFAST and promises to give a 5% speedup on image_cycling.

• Image decoder changes needs to be measured. Do they make anything faster/slower? Do they consume more or less memory? Landed in ​49179ff