Bug 26587 - AOT generic size explosion
Summary: AOT generic size explosion
Alias: None
Product: iOS
Classification: Xamarin
Component: XI runtime ()
Version: master
Hardware: PC Mac OS
: High normal
Target Milestone: Untriaged
Assignee: Zoltan Varga
Depends on:
Reported: 2015-01-30 04:05 UTC by Rolf Bjarne Kvinge [MSFT]
Modified: 2015-04-13 19:23 UTC (History)
3 users (show)

Is this bug a regression?: ---
Last known good build:

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Description Rolf Bjarne Kvinge [MSFT] 2015-01-30 04:05:31 UTC
Test case: https://github.com/wotzisname/open-xml-sdk-xamarin (I used 529ce7014f50dd77f6d342af0450df5f40546700)

Change the architecture to ARMv7 and run on device. It will usually crash either at startup or when tapping the only button (might have to try a couple of times, once in a while it does actually work as well. Adding a couple of CWLs and rebuilding might make it easier to hit too).

The problem seems to be in the OpenXmlSdk.iOS.dll assembly, it's a 6.0MB assembly which turns into 357MB of native assembly and a 100MB object file. A quick look at the symbols seems to indicate many generic instantiations of different enum types:

> nm OpenXmlSdk.iOS.dll.armv7.o | grep EnumValue.*cctor|wc
     531    1593   59002
All those 531 types seems to be a generic type instantiated with different enum types.

> nm OpenXmlSdk.iOS.dll.armv7.o |grep System_Collections_Generic_KeyValuePair|wc
   19467   58401 3700340
This one has classes as well, but I couldn't find one struct instantiation which wasn't an enum.
Comment 1 Rolf Bjarne Kvinge [MSFT] 2015-01-30 04:06:04 UTC
Zoltan, can you have a look?
Comment 3 Zoltan Varga 2015-01-30 04:45:46 UTC
We generate all generic instances we can find the source assembly if they are not instantiated with reference types, thats why there are so many instances here.
Comment 4 Zoltan Varga 2015-01-30 04:53:34 UTC
Generic value sharing is a fallback to avoid situations where no instance is found, we currently only avoid generating instances of the generic collection classes i.e. List/Dictionary because of it, we don't avoid generating instances of user classes.
Comment 5 Zoltan Varga 2015-02-01 16:09:51 UTC
Currently, there is no solution here other than modifying the source code.
Comment 6 Zoltan Varga 2015-04-07 00:37:32 UTC
Cycle6 will include support for sharing these instances.
Comment 7 Zoltan Varga 2015-04-07 23:35:24 UTC
With current master, the object file size is down to 71mb, but the compiled aot image still contains about 70k methods, so a lot of things are still not shared.
Comment 8 Zoltan Varga 2015-04-13 19:23:39 UTC
With mono master, the object file is down to 43mb, and the number of generic methods is down to 160.