Support SameAsFirstInput policy in register allocator when inputs are paired machine registers

Support SameAsFirstInput policy in register allocator when inputs are paired machine registers

BUG=
R=vegorov@google.com

Committed: https://code.google.com/p/dart/source/detail?r=38290

[Vyacheslav Egorov (Google), 2014-07-16 16:26:42]

LGTM with comment

https://codereview.chromium.org/393323004/diff/1/runtime/vm/flow_graph_alloca...
File runtime/vm/flow_graph_allocator.cc (right):

https://codereview.chromium.org/393323004/diff/1/runtime/vm/flow_graph_alloca...
runtime/vm/flow_graph_allocator.cc:1159: locs->set_out(0,
Location::Pair(in_pair->At(0), in_pair->At(1)));
I wonder what happens if you have partial pair location (EAX, R) specified as
input and output having an SameAsFirstInput. I don't think this will build the
right thing.

I suggest prohibiting this to avoid dealing with it now.

[Cutch, 2014-07-16 16:39:29]

https://codereview.chromium.org/393323004/diff/1/runtime/vm/flow_graph_alloca...
File runtime/vm/flow_graph_allocator.cc (right):

https://codereview.chromium.org/393323004/diff/1/runtime/vm/flow_graph_alloca...
runtime/vm/flow_graph_allocator.cc:1159: locs->set_out(0,
Location::Pair(in_pair->At(0), in_pair->At(1)));
On 2014/07/16 16:26:42, Vyacheslav Egorov (Google wrote:
> I wonder what happens if you have partial pair location (EAX, R) specified as
> input and output having an SameAsFirstInput. I don't think this will build the
> right thing.
> 
> I suggest prohibiting this to avoid dealing with it now.

Done.

[Cutch, 2014-07-16 16:45:15]

Committed patchset #3 manually as r38290 (presubmit successful).