AstGraphBuilder puts a constant context in from the beginning.
Also fix bug in merging contexts in environment.

R=mstarzinger@chromium.org
BUG=

Review URL: https://codereview.chromium.org/934293002

Cr-Commit-Position: refs/heads/master@{#26745}

R=mstarzinger@chromium.org
BUG=

Review URL: https://codereview.chromium.org/917583004

Cr-Commit-Position: refs/heads/master@{#26589}

A CompilationInfo constructed from just an Isolate* and a Zone* is in
weird an inconsistent state (calling e.g. flags() on it will crash),
so we need to avoid them. This CL removes almost all of them, the
remaining 2 call sites in (for testing only) will be handled in a
separate CL. Things which have been changed:

  * Linkage is basically a decorator for CallDescriptor now.

  * ChangeLowering doesn't need Linkage at all.

  * JSGenericLowering doesn't need a full CompilationInfo*, just a
    single flag.

  * JSContextSpecializer doesn't need the full CompilationInfo, just a
    Context.

  * Removed unused CompilationInfo from SimplifiedLoweringTester.

This nicely decouples things already a bit more, but there's still
work to do...

Review URL: https://codereview.chromium.org/899803003

Cr-Commit-Position: refs/heads/master@{#26580}

R=bmeurer@chromium.org
TEST=presubmit

Review URL: https://codereview.chromium.org/905293002

Cr-Commit-Position: refs/heads/master@{#26525}

FINAL implies OVERRIDE, which in turn implies virtual, so there's no need to use
more than one of these. The Google C++ style guide even requires this, see
http://google-styleguide.googlecode.com/svn/trunk/cppguide.html#Inheritance.

While we're here, port r24662 to x87.

The net result is that v8 compiles again with a current clang.

BUG=v8:3753
LOG=y

Review URL: https://codereview.chromium.org/797943002

Cr-Commit-Position: refs/heads/master@{#25792}

R=bmeurer@chromium.org
BUG=

Review URL: https://codereview.chromium.org/771713002

Cr-Commit-Position: refs/heads/master@{#25600}

* Add store-chain folding to context specialization.
* Replace all uses of context with constant and then use
  a visitor to find the places to optimize.

BUG=
R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/440053002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22993 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/426233002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22709 ce2b1a6d-e550-0410-aec6-3dcde31c8c00