This is a first step towards reducing the number of stores/loads when suspending/resuming a generator.

Unfortunately, even for an empty generator, we still use 8 register for various things (try-finally, copies of generator object, parser-introduced temporaries). I will try to get rid of these in separate CLs.

Changes:

- SuspendGenerator bytecode now takes register list to save.
- ResumeGenerator was split into two bytecodes:
  * Resume generator reads the state out and marks the generator as
      'executing'.
  * RestoreGeneratorRegisters reloads the registers from
      the generator.
    + this required adding support for output register list.

- Introduced generator_object_ register in the bytecode generator.
  * in subsequent CLs, I will make better use of it, the goal is
      to get rid if the .generator_object local variable.

- Taught register optimizer to flush unassigned registers.

BUG=v8:6379

Review-Url: https://codereview.chromium.org/2894293003
Cr-Commit-Position: refs/heads/master@{#45675}

Instead of calculating the OSR entry point both in the bytecode analysis
and in the bytecode graph builder, calculate it once in the analysis and
use that calculation in the graph builder.

Old TODO from https://codereview.chromium.org/2558093005.

Change-Id: I071bc622beb55dc5eddaee25ef28e21fc4b477f0
Reviewed-on: https://chromium-review.googlesource.com/485899
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44888}

Adds assignment tracking to the bytecode analysis pass, and updates
bytecode graph builder to only create LoopExitValues for assigned
values.

Review-Url: https://codereview.chromium.org/2558093005
Cr-Commit-Position: refs/heads/master@{#41719}

Wrap the liveness bitvectors from the bytecode liveness analysis with a
helper class, which makes the register/accumulator bits explicit.

Review-Url: https://codereview.chromium.org/2552723004
Cr-Commit-Position: refs/heads/master@{#41589}

This allows us to optimise the bytecode liveness analysis to jump
directly to previously seen indices. The analysis is optimised to store
a stack of loop ends (JumpLoop bytecode indices), and iterate through
these indices directly rather than looping through the bytecode array to
find them.

Review-Url: https://codereview.chromium.org/2536653003
Cr-Commit-Position: refs/heads/master@{#41485}

Replaces the graph-based liveness analyzer in the bytecode graph builder
with an initial bytecode-based liveness analysis pass, which is added to
the existing loop extent analysis.

Now the StateValues in the graph have their inputs initialised to
optimized_out, rather than being modified after the graph is built.

Review-Url: https://codereview.chromium.org/2523893003
Cr-Commit-Position: refs/heads/master@{#41355}

Revert of [ignition/turbo] Perform liveness analysis on the bytecodes (patchset #17 id:320001 of https://codereview.chromium.org/2523893003/ )

Reason for revert:
Breaks the build:

https://build.chromium.org/p/client.v8/builders/V8%20Linux%20-%20shared/builds/14886

Original issue's description:
> [ignition/turbo] Perform liveness analysis on the bytecodes
>
> Replaces the graph-based liveness analyzer in the bytecode graph builder
> with an initial bytecode-based liveness analysis pass, which is added to
> the existing loop extent analysis.
>
> Now the StateValues in the graph have their inputs initialised to
> optimized_out, rather than being modified after the graph is built.
>
> Committed: https://crrev.com/1852300954c216c29cf93444430681d213e87925
> Cr-Commit-Position: refs/heads/master@{#41344}

TBR=jarin@chromium.org,rmcilroy@chromium.org,yangguo@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review-Url: https://codereview.chromium.org/2541443002
Cr-Commit-Position: refs/heads/master@{#41346}

Replaces the graph-based liveness analyzer in the bytecode graph builder
with an initial bytecode-based liveness analysis pass, which is added to
the existing loop extent analysis.

Now the StateValues in the graph have their inputs initialised to
optimized_out, rather than being modified after the graph is built.

Review-Url: https://codereview.chromium.org/2523893003
Cr-Commit-Position: refs/heads/master@{#41344}

Now that we have a JumpLoop bytecode, we can heavily simplify the
branch/loop analysis by assuming that only JumpLoop bytecodes are
backwards edges, and performing the loop analysis as a single
(backwards) pass.

This allows us to get rid of the branch analysis entirely, and builds a
framework to do liveness analysis in the same pass.

Review-Url: https://codereview.chromium.org/2519983002
Cr-Commit-Position: refs/heads/master@{#41194}