Fix environment of the optimized version of the _SetValueOf intrinsic.

R=jkummerow@chromium.org
BUG=

Review URL: https://codereview.chromium.org/158723006

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19289 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Mark faster when executing write barriers.

BUG=
R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/159833002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19290 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
More check elimination improvements including partial learning on false branches of CompareMap and better handling of unreachable blocks.

R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/159963002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19300 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Merge remote-tracking branch 'upstream/master'