Fix some bugs that blocked optimizations in the new IRs.

Fix some bugs that blocked optimizations in the new IRs.

- Bad reference counting in tree IR builder.
- Incorrect visit order in StatementRewriter.visitSetField.
- Bad hint assigned in IR builder for GetClosureVariable.

BUG=
R=sigurdm@google.com

Committed: https://code.google.com/p/dart/source/detail?r=42913

[asgerf, 2015-01-15 12:08:00]

asgerf@google.com changed reviewers:
+ sigurdm@google.com

[asgerf, 2015-01-15 12:08:01]

https://codereview.chromium.org/807573003/diff/1/pkg/compiler/lib/src/tree_ir...
File pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart (right):

https://codereview.chromium.org/807573003/diff/1/pkg/compiler/lib/src/tree_ir...
pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart:201: (int index) =>
getVariable(args[index].definition));
getVariableReference() increases readCount.
getVariable() does not.

readCount is now set in addAssignment when we actually do the assignment.

This avoids spurious readCount in cases where the assignment is unnecessary
because register allocation merged the two variables.

[sigurdm, 2015-01-15 12:21:03]

lgtm

https://codereview.chromium.org/807573003/diff/1/pkg/analyzer2dart/test/end2e...
File pkg/analyzer2dart/test/end2end_data.dart (right):

https://codereview.chromium.org/807573003/diff/1/pkg/analyzer2dart/test/end2e...
pkg/analyzer2dart/test/end2end_data.dart:763: var i, v0 = a.iterator;
Why is `i` still here?

https://codereview.chromium.org/807573003/diff/1/pkg/compiler/lib/src/tree_ir...
File pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart (right):

https://codereview.chromium.org/807573003/diff/1/pkg/compiler/lib/src/tree_ir...
pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart:201: (int index) =>
getVariable(args[index].definition));
On 2015/01/15 12:08:00, asgerf wrote:
> getVariableReference() increases readCount.
> getVariable() does not.
> 
> readCount is now set in addAssignment when we actually do the assignment.
> 
> This avoids spurious readCount in cases where the assignment is unnecessary
> because register allocation merged the two variables.
Maybe put this explanation in a comment in the code.

[asgerf, 2015-01-15 13:05:37]

https://codereview.chromium.org/807573003/diff/1/pkg/analyzer2dart/test/end2e...
File pkg/analyzer2dart/test/end2end_data.dart (right):

https://codereview.chromium.org/807573003/diff/1/pkg/analyzer2dart/test/end2e...
pkg/analyzer2dart/test/end2end_data.dart:763: var i, v0 = a.iterator;
On 2015/01/15 12:21:03, sigurdm wrote:
> Why is `i` still here?

Because the shrinking reductions pass currently does not remove dead
continuation parameters. But 'i' should go away once we fix that.

https://codereview.chromium.org/807573003/diff/1/pkg/compiler/lib/src/tree_ir...
File pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart (right):

https://codereview.chromium.org/807573003/diff/1/pkg/compiler/lib/src/tree_ir...
pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart:201: (int index) =>
getVariable(args[index].definition));
On 2015/01/15 12:21:03, sigurdm wrote:
> On 2015/01/15 12:08:00, asgerf wrote:
> > getVariableReference() increases readCount.
> > getVariable() does not.
> > 
> > readCount is now set in addAssignment when we actually do the assignment.
> > 
> > This avoids spurious readCount in cases where the assignment is unnecessary
> > because register allocation merged the two variables.
> Maybe put this explanation in a comment in the code.

Done.

[asgerf, 2015-01-15 15:50:42]

Committed patchset #3 (id:40001) manually as 42913 (presubmit successful).