In certain cases involving auto-generated Dart sources there could be a
huge number of allocated classes which are subtypes of a certain class.
Specializing such cone types to set types, as well as intersection and
union operations on such types may be slow and may severely affect
compilation time. Also, gradually discovering allocated classes in
such cone types may cause a lot of invalidations during analysis.
In order to avoid servere degradation of compilation time in such case,
this change adds WideConeType which works like a ConeType when number of
allocated classes is large, but it doesn't specialize to a SetType and
has more efficient but approximate implementation of union and
intersection.
Uncompressed size of Flutter gallery AOT snapshot (android/arm64):
WideConeType approximation for types with
>32 allocated subtypes: +0.1176%
>64 allocated subtypes: +0.0956%
>128 allocated subtypes: +0.0027%
For now conservative approximation is used when number of allocated
types >128.
TFA time of large app #1: 175s -> 119s (-32%)
TFA time of large app #2: 211s -> 81s (-61.6%)
Snapshot size changes are insignificant.
TEST=Stress tested on precomp bots with
maxAllocatedTypesInSetSpecializations = 3 and 0.
Issue: https://github.com/dart-lang/sdk/issues/42442
Issue: https://github.com/dart-lang/sdk/issues/43299
Change-Id: Idae33205ddda81714e4aeccc7ae292e0164be651
b/154155290, b/177498788, b/177497864
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/179200
Commit-Queue: Alexander Markov <alexmarkov@google.com>
Reviewed-by: Vyacheslav Egorov <vegorov@google.com>
Reviewed-by: Aske Simon Christensen <askesc@google.com>
Alexander Markov
4f96421419