[turbofan] Fix tail call optimization.

[turbofan] Fix tail call optimization.

Tail calls are matched on the graph, with a dedicated tail call
optimization that is actually testable. The instruction selection can
still fall back to a regular if the platform constraints don't allow to
emit a tail call (i.e. the return locations of caller and callee differ
or the callee takes non-register parameters, which is a restriction that
will be removed in the future).

Also explicitly limit tail call optimization to stubs for now and drop
the global flag.

BUG=v8:4076
LOG=n

Committed: https://crrev.com/d21de2a48bc63823876d3f9bf52753f9da0aea6b
Cr-Commit-Position: refs/heads/master@{#28219}

[Benedikt Meurer, 2015-05-05 05:34:11]

bmeurer@chromium.org changed reviewers:
+ jarin@chromium.org

[Benedikt Meurer, 2015-05-05 05:34:11]

Hey Jaro,

This is the initial fix for TCO, making the optimization itself testable and
independent of instruction selection. The instruction selector still decides
whether to actually do a tail call or fall back to a normal call. I'd prefer to
not have that in the instruction selector, but that's up to Sven to decide
whether it's necessary. Currently we don't have any use cases for that anyway.
Once this is decided we can also cleanup the code duplication in VisitCall and
VisitTailCall.

Please take a look.

Thanks,
Benedikt

[Jarin, 2015-05-05 09:15:24]

lgtm.

https://codereview.chromium.org/1114163005/diff/1/src/compiler/arm/instructio...
File src/compiler/arm/instruction-selector-arm.cc (right):

https://codereview.chromium.org/1114163005/diff/1/src/compiler/arm/instructio...
src/compiler/arm/instruction-selector-arm.cc:1177: FrameStateDescriptor*
frame_state_descriptor =
There seems to be some serious overlap with the VisitCall method in this branch.
Could you reuse that code?

[Benedikt Meurer, 2015-05-05 09:40:21]

https://codereview.chromium.org/1114163005/diff/1/src/compiler/arm/instructio...
File src/compiler/arm/instruction-selector-arm.cc (right):

https://codereview.chromium.org/1114163005/diff/1/src/compiler/arm/instructio...
src/compiler/arm/instruction-selector-arm.cc:1177: FrameStateDescriptor*
frame_state_descriptor =
As said, we will unify VisitCall and VisitTailCall, once we have an idea of what
it should look like.

[Benedikt Meurer, 2015-05-05 09:40:25]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2015-05-05 09:40:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1114163005/1

[commit-bot: I haz the power, 2015-05-05 09:43:05]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-05 09:43:19]

Patchset 1 (id:??) landed as
https://crrev.com/d21de2a48bc63823876d3f9bf52753f9da0aea6b
Cr-Commit-Position: refs/heads/master@{#28219}