| commit | 10a3d9f190d41bc4753c3630c5bd22cdd25465a6 | [log] [tgz] |
|---|---|---|
| author | Alexander Markov <alexmarkov@google.com> | Tue Mar 31 15:44:00 2020 +0000 |
| committer | commit-bot@chromium.org <commit-bot@chromium.org> | Tue Mar 31 15:44:00 2020 +0000 |
| tree | 145553977c3782f5c92bd0009dbd7b6e1f724e29 | |
| parent | b4a591ecc952e8ac60b2a07adbcf649b44ebf7ef [diff] |
[vm/nnbd] Do not treat late final fields as immutable
Current implementation of late fields represents all tests for sentinel
value as an explicit LoadField and comparison. As a result, IL with
inlined late final field getter may look like
v23 <- LoadField(v2 . lateFinalField {final}) T{int?}
Branch if StrictCompare:4(===, v23, v16) goto (7, 8)
B7[target]:8
v28 <- StaticCall:14( init:lateFinalField<0> v2) T{int?}
v30 <- LoadField(v2 . lateFinalField {final}) T{int?}
Branch if StrictCompare:16(===, v30, v16) goto (10, 11)
B10[target]:20
goto:26 B12
B11[target]:22
StaticCall:28( _throwNew@0150898<0> v33)
goto:30 B12
B12[join]:24 pred(B10, B11)
StoreInstanceField(v2 . lateFinalField = v28)
goto:32 B9
B8[target]:10
goto:34 B9
B9[join]:12 pred(B8, B12) {
The second LoadField and comparison is needed to verify that initializer
hasn't assigned field value before (in a recursive invocation).
The second LoadField is dominated by the first LoadField, so CSE
replaces v30 with v23 if late final fields are treated as immutable
like all other final instance fields. After that comparison is removed
and check for the repetitive assignment is fully eliminated.
So, the fact that value of final late field is mutated should be
exposed in the IL and slots corresponding to late final fields
should not be marked as immutable.
The following tests began passing:
dartkp-strong-linux-release-x64:language/nnbd/syntax/late_modifier_edge_cases_test was fixed (RuntimeError -> Pass)
dartkp-weak-asserts-linux-release-x64:language/nnbd/syntax/late_modifier_edge_cases_test was fixed (RuntimeError -> Pass)
Change-Id: I4191a5cb4c1a583c8b8ad81d1f42f4cb4821e51a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/141821
Reviewed-by: Vyacheslav Egorov <vegorov@google.com>
Commit-Queue: Alexander Markov <alexmarkov@google.com>
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