commit | c6fe9e21f005537ecfff947a0e5dbab129a17c26 | [log] [tgz] |
---|---|---|
author | Vyacheslav Egorov <vegorov@google.com> | Tue Nov 16 12:48:52 2021 +0000 |
committer | commit-bot@chromium.org <commit-bot@chromium.org> | Tue Nov 16 12:48:52 2021 +0000 |
tree | 54d5554b2e1a5d19c5d18d4821b4f71d660b70eb | |
parent | a643e537fb84e54c1c80d15651fba415fbb8c284 [diff] |
[vm/compiler] Avoid invalid code motion In Dart doing a type check against one value can constrain the type of another value in an indirect fashion. This possibility needs to be taken into account when inserting Redefinitions to inhibit the code motion. This CL addresses two previously ignored situations: * Given a generic container `C<T> c` which holds a value `T v` doing a type check against `c` might narrow the type of `v`. * Given two generic classes `C<T>` and `H<T>`, doing a type-check against an instance of type `C<X> c` might narrow the type of an unrelated instance of `H<X> v` within the same scope. The second situation is currently limited to a situation when we do an invocation on `this` and the target of the call has constrained generic parameter (e.g. because the target of the call is in the subclass which instantiates the base class with a more specific type `class C_ extends C<int>`). Calls on `this` are special because they are allowed to bypass argument type checks which are usually performed due to covariance. In both cases we need to ensure that all uses of `v` which are using narrowed type are pinned to stay within the true successor of the type-check against `c`. Previously we would only insert redefinitions for the value that is being type checked, but this is not enough and this CL tries to address the newly discovered cases: * When replacing loads in load optimizer we must ensure that if replaced load was dependant on the redefinition (and thus was pinned) the replacement is similarly pinned (if the type of the load might have been narrowed). If neccessary we must insert a redefinition for the loaded value itself. * When performing inlining of calls on `this` we must insert redefinitions for all parameters that might have their types narrowed. * When replacing phis which have redefinitions as all inputs. Fixes https://github.com/flutter/flutter/issues/91370 Fixes https://github.com/dart-lang/sdk/issues/43652 TEST=vm/dart{,_2}/flutter_regress_91370_il_test Cq-Include-Trybots: luci.dart.try:vm-kernel-precomp-linux-debug-x64-try,vm-kernel-precomp-linux-product-x64-try,vm-kernel-precomp-linux-release-x64-try Change-Id: I89c1f165615dd827102e9f6af90365af7d8f32b2 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/219241 Commit-Queue: Slava Egorov <vegorov@google.com> Reviewed-by: Alexander Markov <alexmarkov@google.com>
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