[turbofan] Add support for pushing returns into merges.

[turbofan] Add support for pushing returns into merges.

This will enable tail call optimization even across inlining. Plus it
might enable some other interesting optimizations as well. In order to
avoid blowing up the generated code, we can still canonicalize the
epilogue in the CodeGenerator, similar to what fullcodegen does.

R=jarin@chromium.org

Committed: https://crrev.com/7337021e54d8a15183c2d4247b2ed83d9b5120ef
Cr-Commit-Position: refs/heads/master@{#29311}

[Benedikt Meurer, 2015-06-26 07:45:32]

Hey Jaro,

This is a CL for danno's code stubs. Please take a look.

Thanks,
Benedikt

[Jarin, 2015-06-26 07:52:44]

lgtm

[Jarin, 2015-06-26 07:55:31]

https://codereview.chromium.org/1215623002/diff/1/src/compiler/common-operato...
File src/compiler/common-operator-reducer.cc (right):

https://codereview.chromium.org/1215623002/diff/1/src/compiler/common-operato...
src/compiler/common-operator-reducer.cc:273: value->InputAt(value->InputCount()
- 1) == control &&
Please use NodeProperties::GetControlInput here.

[Benedikt Meurer, 2015-06-26 07:56:59]

https://codereview.chromium.org/1215623002/diff/1/src/compiler/common-operato...
File src/compiler/common-operator-reducer.cc (right):

https://codereview.chromium.org/1215623002/diff/1/src/compiler/common-operato...
src/compiler/common-operator-reducer.cc:273: value->InputAt(value->InputCount()
- 1) == control &&
On 2015/06/26 07:55:31, jarin wrote:
> Please use NodeProperties::GetControlInput here.

Done.

[Benedikt Meurer, 2015-06-26 07:57:03]

The CQ bit was checked by bmeurer@chromium.org

[Benedikt Meurer, 2015-06-26 07:57:03]

The patchset sent to the CQ was uploaded after l-g-t-m from jarin@chromium.org
Link to the patchset: https://codereview.chromium.org/1215623002/#ps20001
(title: "Use NodeProperties::GetControlInput.")

[commit-bot: I haz the power, 2015-06-26 07:57:10]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1215623002/20001

[commit-bot: I haz the power, 2015-06-26 08:20:58]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-06-26 08:21:09]

Patchset 2 (id:??) landed as
https://crrev.com/7337021e54d8a15183c2d4247b2ed83d9b5120ef
Cr-Commit-Position: refs/heads/master@{#29311}