tree 8fd553b95a7e1b517268ba64156586bd9609a3d3
parent 9847e7fbe62a1e4104228922885926c7a92cacb1
author Martin Kustermann <kustermann@google.com> 1616684683 +0000
committer commit-bot@chromium.org <commit-bot@chromium.org> 1616684683 +0000

Reland "[vm/compiler] Always allow CSE of LoadStaticField & loosen assertion in AllowsCSE"

Loosening of assertion:

There is no guarantee that a static-final field has been initialized by
the time a function is compiled (in optimized mode) that uses such a
field.

We should therefore loosen the ASSERT to not require the field to be
initialized and rather allows CSE

Enabling of CSE:

In the past we had separate InitStaticField and LoadStaticField. The
load itself had no side-effects and could therefore be moved
arbitrarily. Though we couldn't allow it to be moved before it's
InitStaticField. This dependency was not explicitly made and we
therefore disabled CSE / LICM if the actual field was not initialized
(or field may be reset) - see [0].

Though after merging of InitStaticField and LoadStaticField in [1] there
is no longer a need for tracking any dependencies: The side-effects
of InitStaticField are now reported by LoadStaticField.
=> We can therefore always allow CSE of LoadStaticFieldinstr and
any code motion would respect side-effects of the instruction.

[0] https://codereview.chromium.org/1497783002
[1] https://dart-review.googlesource.com/c/sdk/+/148283

TEST=Fixes flaky test.

Closes https://github.com/dart-lang/sdk/issues/45133
Closes https://github.com/dart-lang/sdk/issues/45446

Change-Id: I4a699e9b1dc9dfec9a91208ed78ed0a0c41f5cad
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/192924
Reviewed-by: Vyacheslav Egorov <vegorov@google.com>
Commit-Queue: Martin Kustermann <kustermann@google.com>