Implement lowering of JSLoadContext to machine operators.

Implement lowering of JSLoadContext to machine operators.

R=titzer@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=22748

[titzer, 2014-07-31 11:02:17]

lgtm other than being wrong

https://codereview.chromium.org/433853002/diff/1/src/compiler/js-generic-lowe...
File src/compiler/js-generic-lowering.cc (right):

https://codereview.chromium.org/433853002/diff/1/src/compiler/js-generic-lowe...
src/compiler/js-generic-lowering.cc:373: for (int i = 0; i < access.depth();
++i) {
Please leave a TODO here because I think we want to lower this to
SimplifiedOperators first so that we have a little more information for GVN and
load/store elimination.

https://codereview.chromium.org/433853002/diff/1/src/compiler/js-generic-lowe...
src/compiler/js-generic-lowering.cc:376: machine()->Load(machine()->word()),
You need kMachineTagged here, otherwise the register allocator won't track it as
a pointer.

[Michael Starzinger, 2014-07-31 11:18:32]

Addressed comments. Nice catch. Landing.

https://codereview.chromium.org/433853002/diff/1/src/compiler/js-generic-lowe...
File src/compiler/js-generic-lowering.cc (right):

https://codereview.chromium.org/433853002/diff/1/src/compiler/js-generic-lowe...
src/compiler/js-generic-lowering.cc:373: for (int i = 0; i < access.depth();
++i) {
On 2014/07/31 11:02:16, titzer wrote:
> Please leave a TODO here because I think we want to lower this to
> SimplifiedOperators first so that we have a little more information for GVN
and
> load/store elimination.

Done.

https://codereview.chromium.org/433853002/diff/1/src/compiler/js-generic-lowe...
src/compiler/js-generic-lowering.cc:376: machine()->Load(machine()->word()),
On 2014/07/31 11:02:16, titzer wrote:
> You need kMachineTagged here, otherwise the register allocator won't track it
as
> a pointer.

Done. Nice catch.

[Michael Starzinger, 2014-07-31 11:20:49]

Committed patchset #2 manually as r22748 (tree was closed).