Automatically assign temporary indices to definitions in the IL.

Automatically assign temporary indices to definitions in the IL.

When added to the graph, automatically assign a temporary index (== stack
height) to definitions.

R=srdjan@google.com
BUG=
TEST=

Committed: https://code.google.com/p/dart/source/detail?r=7269

[Kevin Millikin (Google), 2012-05-02 13:53:25]

This requires incrementing the stack height for every definition and
decrementing for every use.

The instructions and computations are responsible for reporting the number of
uses they consume; this is encoded as a template parameter in many cases
(reason: it's more declarative than writing code to implement it).

(There are still a few occurrences of the old TempVal.  This current
implementation doesn't allow for any kind of location other than stack, so a
simple int index is (currently) unambiguous).

[srdjan, 2012-05-02 22:07:32]

LGTM with comments/questions

http://codereview.chromium.org/10316005/diff/1/runtime/vm/flow_graph_builder.cc
File runtime/vm/flow_graph_builder.cc (right):

http://codereview.chromium.org/10316005/diff/1/runtime/vm/flow_graph_builder....
runtime/vm/flow_graph_builder.cc:98: exit_ = false_exit;  // May be NULL.
When is it possible to have both true and false exits null?

http://codereview.chromium.org/10316005/diff/1/runtime/vm/flow_graph_builder.h
File runtime/vm/flow_graph_builder.h (right):

http://codereview.chromium.org/10316005/diff/1/runtime/vm/flow_graph_builder....
runtime/vm/flow_graph_builder.h:176: void DeallocateTempIndex(intptr_t n = 1) {
Remove default value, please.

http://codereview.chromium.org/10316005/diff/1/runtime/vm/intermediate_langua...
File runtime/vm/intermediate_language.h (right):

http://codereview.chromium.org/10316005/diff/1/runtime/vm/intermediate_langua...
runtime/vm/intermediate_language.h:98: 
I think templates below are nifty but an overkill for what you are attempting to
do. Could you please explain the advantage when compared to conventional
solution (an input_number field in computation, and appropriate accessors).

[Kevin Millikin (Google), 2012-05-03 08:26:23]

I'll commit as is and we can talk about any better solutions than the templates.

http://codereview.chromium.org/10316005/diff/1/runtime/vm/flow_graph_builder.cc
File runtime/vm/flow_graph_builder.cc (right):

http://codereview.chromium.org/10316005/diff/1/runtime/vm/flow_graph_builder....
runtime/vm/flow_graph_builder.cc:98: exit_ = false_exit;  // May be NULL.
On 2012/05/02 22:07:32, srdjan wrote:
> When is it possible to have both true and false exits null?

An 'if' that returns in both branches, for instance.

http://codereview.chromium.org/10316005/diff/1/runtime/vm/flow_graph_builder.h
File runtime/vm/flow_graph_builder.h (right):

http://codereview.chromium.org/10316005/diff/1/runtime/vm/flow_graph_builder....
runtime/vm/flow_graph_builder.h:176: void DeallocateTempIndex(intptr_t n = 1) {
On 2012/05/02 22:07:32, srdjan wrote:
> Remove default value, please.

Yikes, I meant to do that.  Thanks.

http://codereview.chromium.org/10316005/diff/1/runtime/vm/intermediate_langua...
File runtime/vm/intermediate_language.h (right):

http://codereview.chromium.org/10316005/diff/1/runtime/vm/intermediate_langua...
runtime/vm/intermediate_language.h:98: 
On 2012/05/02 22:07:32, srdjan wrote:
> I think templates below are nifty but an overkill for what you are attempting
to
> do. Could you please explain the advantage when compared to conventional
> solution (an input_number field in computation, and appropriate accessors).

The primary advantage is that it eliminates a lot of boilerplate in the IL
classes.  We'll eventually want to be able to iterate all inputs, for example,
and the templates are (one way) to eliminate writing per-class iteration code.