VM: Fix incorrect canonicalization rule for `UnboxedIntConverterInstr`.

VM: Fix incorrect canonicalization rule for `UnboxedIntConverterInstr`.

The rule assumed that `UnboxedIntConverter(U->V, UnboxedIntConverter(V->U, v))` is
equal to `v` which is incorrect if the first convertion is truncating and
V is a larger representation (Mint) than U (Int32 or Uint32).

Now canonicalization rule takes into account if the first convertion is
truncating and does not try to short-circuit such convertions.

Fixes https://github.com/dart-lang/sdk/issues/29137

R=kustermann@google.com
BUG=http://dartbug.com/29137

Committed: https://github.com/dart-lang/sdk/commit/41b5d7c6de510bc595a1379b6072fcd9d7f621ba

[kustermann, 2017-04-03 15:31:48]

LGTM, nice catch!

https://codereview.chromium.org/2793003002/diff/1/tests/language/vm/regress_2...
File tests/language/vm/regress_29137_vm_test.dart (right):

https://codereview.chromium.org/2793003002/diff/1/tests/language/vm/regress_2...
tests/language/vm/regress_29137_vm_test.dart:20: var mod_shift = shift & 31;
final :)

[Vyacheslav Egorov (Google), 2017-04-03 16:51:10]

Description was changed from

==========
VM: Fix incorrect canonicalization rule for `UnboxedIntConverterInstr`.

The rule assumed that `UnboxedIntConverter(U->V, UnboxedIntConverter(V->U, v))`
is
equal to `v` which is incorrect if the first convertion is truncating and
V is a larger representation (Mint) than U (Int32 or Uint32).

Now canonicalization rule takes into account if the first convertion is
truncating and does not try to short-circuit such convertions.

Fixes https://github.com/dart-lang/sdk/issues/29137

R=kustermann@google.com
BUG=http://dartbug.com/29137
==========

to

==========
VM: Fix incorrect canonicalization rule for `UnboxedIntConverterInstr`.

The rule assumed that `UnboxedIntConverter(U->V, UnboxedIntConverter(V->U, v))`
is
equal to `v` which is incorrect if the first convertion is truncating and
V is a larger representation (Mint) than U (Int32 or Uint32).

Now canonicalization rule takes into account if the first convertion is
truncating and does not try to short-circuit such convertions.

Fixes https://github.com/dart-lang/sdk/issues/29137

R=kustermann@google.com
BUG=http://dartbug.com/29137

Committed:
https://github.com/dart-lang/sdk/commit/41b5d7c6de510bc595a1379b6072fcd9d7f621ba
==========

[Vyacheslav Egorov (Google), 2017-04-03 16:51:11]

Committed patchset #2 (id:20001) manually as
41b5d7c6de510bc595a1379b6072fcd9d7f621ba (presubmit successful).