[turbofan] Implement simplistic checkpoint reducer.

[turbofan] Implement simplistic checkpoint reducer.

This adds a very simplistic reduction of {CheckPoint} nodes via the new
{CheckpointElimination}, eliminating redundant check points that appear
in an effect chain of operations that are all {kNoWrite}. Such a chain
allows an arbitrary check point to be chosen. The current approach will
end up choosing the first one for all deopts in the chain.

R=bmeurer@chromium.org
TEST=unittests/CheckpointEliminationTest.CheckPointChain
BUG=v8:5021
Committed: https://crrev.com/7ecf1a059b4f264a3521bd4e16828248ece0606f
Cr-Commit-Position: refs/heads/master@{#36634}

[Michael Starzinger, 2016-05-31 14:57:55]

PTAL. Moved into separate reducer as per offline comment.

[Michael Starzinger, 2016-05-31 14:59:09]

Description was changed from

==========
[turbofan] Implement simplistic checkpoint reducer.

This adds a very simplistic reduction of {CheckPoint} nodes to the
{CommonOperatorReducer}, eliminating redundant check points that appear
in an effect chain of operations that are all {kNoWrite}. Such a chain
allows an arbitrary check point to be chosen. The current approach will
end up choosing the first one for all deopts in the chain.

R=bmeurer@chromium.org
TEST=unittests/CommonOperatorReducerTest.CheckPointChain
BUG=v8:5021
==========

to

==========
[turbofan] Implement simplistic checkpoint reducer.

This adds a very simplistic reduction of {CheckPoint} nodes via the new
{CheckpointElimination}, eliminating redundant check points that appear
in an effect chain of operations that are all {kNoWrite}. Such a chain
allows an arbitrary check point to be chosen. The current approach will
end up choosing the first one for all deopts in the chain.

R=bmeurer@chromium.org
TEST=unittests/CheckpointEliminationTest.CheckPointChain
BUG=v8:5021
==========

[Benedikt Meurer, 2016-06-01 04:05:22]

LGTM with comment.

We should really rename CheckPoint to Checkpoint, tho, I agree.

https://codereview.chromium.org/2022913003/diff/20001/src/compiler/checkpoint...
File src/compiler/checkpoint-elimination.cc (right):

https://codereview.chromium.org/2022913003/diff/20001/src/compiler/checkpoint...
src/compiler/checkpoint-elimination.cc:35: DCHECK_EQ(IrOpcode::kCheckPoint,
node->opcode());
The DCHECK_EQ is exactly the same as the check in the line above, so let's drop
that.

[Michael Starzinger, 2016-06-01 08:11:10]

Thanks! Addressed comments. Will do the rename in a separate CL.

https://codereview.chromium.org/2022913003/diff/20001/src/compiler/checkpoint...
File src/compiler/checkpoint-elimination.cc (right):

https://codereview.chromium.org/2022913003/diff/20001/src/compiler/checkpoint...
src/compiler/checkpoint-elimination.cc:35: DCHECK_EQ(IrOpcode::kCheckPoint,
node->opcode());
On 2016/06/01 04:05:22, Benedikt Meurer wrote:
> The DCHECK_EQ is exactly the same as the check in the line above, so let's
drop
> that.

Done.

[Michael Starzinger, 2016-06-01 08:31:58]

The CQ bit was checked by mstarzinger@chromium.org

[Michael Starzinger, 2016-06-01 08:31:59]

The patchset sent to the CQ was uploaded after l-g-t-m from bmeurer@chromium.org
Link to the patchset: https://codereview.chromium.org/2022913003/#ps40001
(title: "Addressed comments.")

[commit-bot: I haz the power, 2016-06-01 08:32:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2022913003/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/2022913003/40001

[commit-bot: I haz the power, 2016-06-01 08:38:40]

Description was changed from

==========
[turbofan] Implement simplistic checkpoint reducer.

This adds a very simplistic reduction of {CheckPoint} nodes via the new
{CheckpointElimination}, eliminating redundant check points that appear
in an effect chain of operations that are all {kNoWrite}. Such a chain
allows an arbitrary check point to be chosen. The current approach will
end up choosing the first one for all deopts in the chain.

R=bmeurer@chromium.org
TEST=unittests/CheckpointEliminationTest.CheckPointChain
BUG=v8:5021
==========

to

==========
[turbofan] Implement simplistic checkpoint reducer.

This adds a very simplistic reduction of {CheckPoint} nodes via the new
{CheckpointElimination}, eliminating redundant check points that appear
in an effect chain of operations that are all {kNoWrite}. Such a chain
allows an arbitrary check point to be chosen. The current approach will
end up choosing the first one for all deopts in the chain.

R=bmeurer@chromium.org
TEST=unittests/CheckpointEliminationTest.CheckPointChain
BUG=v8:5021
==========

[commit-bot: I haz the power, 2016-06-01 08:38:41]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2016-06-01 08:39:16]

Description was changed from

==========
[turbofan] Implement simplistic checkpoint reducer.

This adds a very simplistic reduction of {CheckPoint} nodes via the new
{CheckpointElimination}, eliminating redundant check points that appear
in an effect chain of operations that are all {kNoWrite}. Such a chain
allows an arbitrary check point to be chosen. The current approach will
end up choosing the first one for all deopts in the chain.

R=bmeurer@chromium.org
TEST=unittests/CheckpointEliminationTest.CheckPointChain
BUG=v8:5021
==========

to

==========
[turbofan] Implement simplistic checkpoint reducer.

This adds a very simplistic reduction of {CheckPoint} nodes via the new
{CheckpointElimination}, eliminating redundant check points that appear
in an effect chain of operations that are all {kNoWrite}. Such a chain
allows an arbitrary check point to be chosen. The current approach will
end up choosing the first one for all deopts in the chain.

R=bmeurer@chromium.org
TEST=unittests/CheckpointEliminationTest.CheckPointChain
BUG=v8:5021

Committed: https://crrev.com/7ecf1a059b4f264a3521bd4e16828248ece0606f
Cr-Commit-Position: refs/heads/master@{#36634}
==========

[commit-bot: I haz the power, 2016-06-01 08:39:17]

Patchset 3 (id:??) landed as
https://crrev.com/7ecf1a059b4f264a3521bd4e16828248ece0606f
Cr-Commit-Position: refs/heads/master@{#36634}