ARM64: use jssp for stack slots

ARM64: use jssp for stack slots

R=ulan@chromium.org, bmeurer@chromium.org

[vincent.belliard, 2014-04-30 11:00:43]

Access stack slots via jssp instead of fp when it's possible and needed.
The aim is to remove accesses with two instructions (one to load the index in a
register).

There is no changes in benchmarks. However, the generated code is smaller. For
example, for Octane2, it removes 15138 instructions from the generated code (20%
of the load/store for stack slots).

[Benedikt Meurer, 2014-04-30 17:22:57]

LGTM

[Toon Verwaest, 2015-03-23 14:17:23]

verwaest@chromium.org changed reviewers:
+ verwaest@chromium.org

[Toon Verwaest, 2015-03-23 14:17:24]

As far as I can tell this is broken. See
http://build.chromium.org/p/tryserver.v8/builders/v8_linux_arm64_rel/builds/4101
for a repro.

The reason why it is failing is that GenerateCallFunction pushes arguments a
single time, before branching on the function to choose the correct HInstruction
to use for the call. Given that there are 2 call instructions for the single
push (HInvokeFunction and HCallFunction) we think we're not in the push-case
anymore in DoInvokeFunction. DoCallFunction already reset after_push_argument_
to false. This causes us to load the value relative to the stack pointer at an
incorrect offset.