More specifically on 64-bit platforms, when other heuristic fail:
- in AOT mode unbox all int typed phis.
- in JIT mode unbox all non-Smi int typed phis i.e. mixed
Mint/Smi phis.
This brings treatment of int phis closer to how we treat other
boxed phis.
This considerably improves AOT code quality for loops which
our current conservative heuristic does not currently hit,
for example:
void foo(int start, int end) {
for (var i = start; i < end; i++) {
}
}
Code like this would use a boxed Phi previously which does not make
sense.
In JIT mode to really benefit from aggressive unboxing we
might need to shift from over-reliance on Smi operations, e.g.
when phi is unboxed we want to cascade that through and unbox
operations which are performed on it transitively. This requires
much more sophisticated algorithm and is outside of scope for this
change.
In AOT we in general treat all arithmetic operations as operations
over 64-bit int values so unboxing phis makes more sense.
As a result of this change we see small improvement in code size:
flutter_gallery_app_so_gzip_size -0.2392%
TEST=ci
Cq-Include-Trybots: luci.dart.try:vm-kernel-precomp-linux-release-x64-try
Change-Id: Iae9a16f353e53f649da4e665d2812ad47099a674
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/187860
Commit-Queue: Vyacheslav Egorov <vegorov@google.com>
Reviewed-by: Alexander Markov <alexmarkov@google.com>
Vyacheslav Egorov