Rework flow graph construction.

Rework flow graph construction.

The flow graph has been simplified to remove the special branch, join,
and exit nodes.  All nodes are now basic blocks (possibly empty to
preserve edge-split form) with a distinguished entry and exit block.

Most trivial expressions are not added to the flow graph as
instructions.  The assigned variable analyzer has been changed to
sometimes work right-to-left so that right subexpressions can be
marked as trivial.

The reaching definitions analysis has been temporarily removed, and
the analyses that depended on it (primitivity analysis, dead code
marking) as well.

Committed: http://code.google.com/p/v8/source/detail?r=4307

[fschneider, 2010-03-29 13:49:59]

LGTM with comments addressed.

http://codereview.chromium.org/1530003/diff/1/6
File src/data-flow.cc (right):

http://codereview.chromium.org/1530003/diff/1/6#newcode668
src/data-flow.cc:668: ProcessExpression(expr->key());
That should be 

ProcessExpression(expr->obj());

http://codereview.chromium.org/1530003/diff/1/8
File src/flow-graph.cc (right):

http://codereview.chromium.org/1530003/diff/1/8#newcode262
src/flow-graph.cc:262: current_->AddInstruction(expr);
UNREACHABLE() here? Since literals are always trivial, do you ever visit them?

http://codereview.chromium.org/1530003/diff/1/9
File src/flow-graph.h (right):

http://codereview.chromium.org/1530003/diff/1/9#newcode53
src/flow-graph.h:53: BasicBlock(BasicBlock* predecessor)
explicit for 1-argument constructors?

http://codereview.chromium.org/1530003/diff/1/9#newcode113
src/flow-graph.h:113: ZoneList<AstNode*> instructions_;
We probably need an accessor for instructions_. But it's ok to add it on first
use in a separate change.

[Kevin Millikin (Chromium), 2010-03-29 14:22:53]

http://codereview.chromium.org/1530003/diff/1/6
File src/data-flow.cc (right):

http://codereview.chromium.org/1530003/diff/1/6#newcode668
src/data-flow.cc:668: ProcessExpression(expr->key());
On 2010/03/29 13:49:59, fschneider wrote:
> That should be 
> 
> ProcessExpression(expr->obj());
> 

Thank you.

http://codereview.chromium.org/1530003/diff/1/9
File src/flow-graph.h (right):

http://codereview.chromium.org/1530003/diff/1/9#newcode53
src/flow-graph.h:53: BasicBlock(BasicBlock* predecessor)
On 2010/03/29 13:49:59, fschneider wrote:
> explicit for 1-argument constructors?

Done.