A simpler scheme for garbage collection of ureachable phi inputs.

A simpler scheme for garbage collection of ureachable phi inputs.

Simplify the garbage collection of unreachable phi inputs.  Assign immutable
block ids to basic blocks and ensure that both predecessor blocks and phi
inputs are kept sorted by block id.

R=vegorov@google.com
BUG=

Committed: https://code.google.com/p/dart/source/detail?r=12621

[Kevin Millikin (Google), 2012-09-20 08:21:08]

Ian, can you take a look at this?

[zerny-google, 2012-09-20 08:43:53]

lgtm with one question.

https://codereview.chromium.org/10939036/diff/3001/runtime/vm/flow_graph_buil...
File runtime/vm/flow_graph_builder.cc (right):

https://codereview.chromium.org/10939036/diff/3001/runtime/vm/flow_graph_buil...
runtime/vm/flow_graph_builder.cc:2517:
catch_entry->set_catch_try_index(try_index);
Why use a setter for catch_try_index? Can it change later?

[Vyacheslav Egorov (Google), 2012-09-21 12:52:59]

https://chromiumcodereview.appspot.com/10939036/diff/1/runtime/vm/flow_graph_...
File runtime/vm/flow_graph_optimizer.cc (right):

https://chromiumcodereview.appspot.com/10939036/diff/1/runtime/vm/flow_graph_...
runtime/vm/flow_graph_optimizer.cc:2407: BranchInstr* branch =
i.Current()->AsBranch();
I find it very confusing that branch case in inside the loop while it can only
occur for the last instruction in the block.

https://chromiumcodereview.appspot.com/10939036/diff/1/runtime/vm/intermediat...
File runtime/vm/intermediate_language.cc (right):

https://chromiumcodereview.appspot.com/10939036/diff/1/runtime/vm/intermediat...
runtime/vm/intermediate_language.cc:490: (predecessors_[index]->block_id() <
pred_id)) {
assert here that there is not block with pred_id in the array.

[Kevin Millikin (Google), 2012-09-21 13:08:04]

https://chromiumcodereview.appspot.com/10939036/diff/1/runtime/vm/flow_graph_...
File runtime/vm/flow_graph_optimizer.cc (right):

https://chromiumcodereview.appspot.com/10939036/diff/1/runtime/vm/flow_graph_...
runtime/vm/flow_graph_optimizer.cc:2407: BranchInstr* branch =
i.Current()->AsBranch();
I'll move it out.

https://chromiumcodereview.appspot.com/10939036/diff/1/runtime/vm/intermediat...
File runtime/vm/intermediate_language.cc (right):

https://chromiumcodereview.appspot.com/10939036/diff/1/runtime/vm/intermediat...
runtime/vm/intermediate_language.cc:490: (predecessors_[index]->block_id() <
pred_id)) {
OK.