Fuse Comparison->BooleanNegate->Branch.

Fuse Comparison->BooleanNegate->Branch.
Committed: https://code.google.com/p/dart/source/detail?r=8914

[Florian Schneider, 2012-06-20 10:55:17]

I think this kind of optimization should be really done in the flow graph
builder where we can immediately generate a CompareAndBranch instruction.

[Vyacheslav Egorov (Google), 2012-06-20 12:17:40]

lgtm as a temporary solution.

we can potentially fuse it in the graph builder.

https://chromiumcodereview.appspot.com/10559072/diff/2004/runtime/vm/flow_gra...
File runtime/vm/flow_graph_optimizer.cc (left):

https://chromiumcodereview.appspot.com/10559072/diff/2004/runtime/vm/flow_gra...
runtime/vm/flow_graph_optimizer.cc:518: TryFuseComparisonWithBranch(comp);
there is a special NaN branch inside the Double relational op. Just negating the
branch itself is not enough.

[srdjan, 2012-06-20 16:16:07]

https://chromiumcodereview.appspot.com/10559072/diff/2004/runtime/vm/flow_gra...
File runtime/vm/flow_graph_optimizer.cc (left):

https://chromiumcodereview.appspot.com/10559072/diff/2004/runtime/vm/flow_gra...
runtime/vm/flow_graph_optimizer.cc:518: TryFuseComparisonWithBranch(comp);
On 2012/06/20 12:17:40, Vyacheslav Egorov (Google) wrote:
> there is a special NaN branch inside the Double relational op. Just negating
the
> branch itself is not enough.

Thanks for catching it. Added following code in intermediate_language_<arch>.cc:
     BlockEntryInstr* nan_result = branch->is_negated() ?
        branch->true_successor() : branch->false_successor();
    __ j(PARITY_EVEN, compiler->GetBlockLabel(nan_result));

[srdjan, 2012-06-20 16:16:56]

On 2012/06/20 10:55:17, Florian Schneider wrote:
> I think this kind of optimization should be really done in the flow graph
> builder where we can immediately generate a CompareAndBranch instruction.

You may have a point, and we should discuss this soon.