Refactor SsaBranchBuilder.

Refactor SsaBranchBuilder.

Committed: https://code.google.com/p/dart/source/detail?r=9549

[Lasse Reichstein Nielsen, 2012-07-11 12:10:53]

LGTM

https://chromiumcodereview.appspot.com/10693143/diff/1/lib/compiler/implement...
File lib/compiler/implementation/ssa/builder.dart (right):

https://chromiumcodereview.appspot.com/10693143/diff/1/lib/compiler/implement...
lib/compiler/implementation/ssa/builder.dart:3437: /** Returns true if the
locals have been copied. */
What does it mean to "have been copied"?
Can we use the originals again, or can't we? I'm *guessing* that "have been
copied" means that the original is free to be reused.

Generally, the "copy" word doesn't carry much meaning, it's referring to a
technical thing we do in some cases, but not to why we do it or what it means.
Is there a better term?
E.g., this function returns true if the fromBranch's exitLocals have not been
modified or stored, so they are free to reuse.
The "needsCopy" could be reversed to "mayReuse" with a comment that it refers to
fromBranch.exitLocals. And the return value can be reversed to mean "did reuse".

https://chromiumcodereview.appspot.com/10693143/diff/1/lib/compiler/implement...
lib/compiler/implementation/ssa/builder.dart:3438: bool mergeLocals(SsaBranch
fromBranch, SsaBranch toBranch, [needsCopy]) {
Type 'bool' on needsCopy.

[floitsch, 2012-07-11 12:24:19]

https://chromiumcodereview.appspot.com/10693143/diff/1/lib/compiler/implement...
File lib/compiler/implementation/ssa/builder.dart (right):

https://chromiumcodereview.appspot.com/10693143/diff/1/lib/compiler/implement...
lib/compiler/implementation/ssa/builder.dart:3437: /** Returns true if the
locals have been copied. */
On 2012/07/11 12:10:53, Lasse Reichstein Nielsen wrote:
> What does it mean to "have been copied"?
> Can we use the originals again, or can't we? I'm *guessing* that "have been
> copied" means that the original is free to be reused.
> 
> Generally, the "copy" word doesn't carry much meaning, it's referring to a
> technical thing we do in some cases, but not to why we do it or what it means.
> Is there a better term?
> E.g., this function returns true if the fromBranch's exitLocals have not been
> modified or stored, so they are free to reuse.
> The "needsCopy" could be reversed to "mayReuse" with a comment that it refers
to
> fromBranch.exitLocals. And the return value can be reversed to mean "did
reuse".

Did not change the return type, but inverted the argument. Now
"mayReuseFromLocals".

https://chromiumcodereview.appspot.com/10693143/diff/1/lib/compiler/implement...
lib/compiler/implementation/ssa/builder.dart:3438: bool mergeLocals(SsaBranch
fromBranch, SsaBranch toBranch, [needsCopy]) {
On 2012/07/11 12:10:53, Lasse Reichstein Nielsen wrote:
> Type 'bool' on needsCopy.

Done.