dart2dart: Copy propagation in dart_tree.

dart2dart: Copy propagation in dart_tree.

Moving assignments w := v are eliminated by assigning directly to w at the definition of v.

Since we can't check if v is live after the assignment, this only clicks when we have the unique use of v.

BUG=
R=kmillikin@google.com, sigurdm@google.com

Committed: https://code.google.com/p/dart/source/detail?r=38008

[Kevin Millikin (Google), 2014-07-04 10:37:49]

LGTM.

[sigurdm, 2014-07-04 10:56:51]

lgtm

https://codereview.chromium.org/368363002/diff/1/sdk/lib/_internal/compiler/i...
File sdk/lib/_internal/compiler/implementation/dart_backend/dart_tree.dart
(right):

https://codereview.chromium.org/368363002/diff/1/sdk/lib/_internal/compiler/i...
sdk/lib/_internal/compiler/implementation/dart_backend/dart_tree.dart:1732: *
nothing no optimization could be performed.
if nothing no -> if no

[asgerf, 2014-07-04 10:58:37]

https://codereview.chromium.org/368363002/diff/1/sdk/lib/_internal/compiler/i...
File sdk/lib/_internal/compiler/implementation/dart_backend/dart_tree.dart
(right):

https://codereview.chromium.org/368363002/diff/1/sdk/lib/_internal/compiler/i...
sdk/lib/_internal/compiler/implementation/dart_backend/dart_tree.dart:1732: *
nothing no optimization could be performed.
On 2014/07/04 10:56:51, sigurdm wrote:
> if nothing no -> if no

Thanks.

[asgerf, 2014-07-04 10:59:58]

Committed patchset #3 manually as r38008 (presubmit successful).