Dead Store Elimination (DSE) propagates "dead store" state backwards
across basic blocks to predecessors. If place is defined in a loop
(either its instance or index are defined in a loop), propagating
"dead store" state across backedge of the loop is incorrect, as each
loop iteration effectively has its own place.
This bug is fixed by disabling propagation of "dead store"
state beyond defining blocks of instance and index of a place.
This is done by setting bits in "live_in" of the blocks corresponding
to the instance and index definitions of a place.
TEST=runtime/tests/vm/dart/regress_55607_test.dart
Fixes https://github.com/dart-lang/sdk/issues/55607
Change-Id: I223ff433daa3d7bcafefc9d91360b16c9554964e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/365302
Commit-Queue: Alexander Markov <alexmarkov@google.com>
Reviewed-by: Slava Egorov <vegorov@google.com>
Alexander Markov
95d96cf06d