Use smi zero instead of undefine_value to zap dead weak cells.

It is faster to test for smi zero from generated code.

BUG=
R=erikcorry@chromium.org

Review URL: https://codereview.chromium.org/637253004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24758 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Fix Win64 after r24758.

BUG=
TBR=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/663343002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24759 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Fix use-of-uninitialized-value introduced in r24700

LOG=N
BUG=chromium:425146
R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/665243002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24760 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Remove unused GetConstructor

BUG=
R=ishell@chromium.org

Review URL: https://codereview.chromium.org/663033004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24761 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Revert "Assign bailout and type feedback IDs in a post-pass"

This reverts r24757, which breaks the ARM64 simulator build.
Simple repro:

   out/arm64.debug/d8 -e 'eval("(function(){ const x; var x; })")'

TBR=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/652543006

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24762 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Fix leak in d8.

R=bmeurer@chromium.org
TBR=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/652403003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24763 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
[x86] Select better left operand for comparisons.

R=dcarney@chromium.org

Review URL: https://codereview.chromium.org/667933002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24764 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Perf tests for harmony string functions.

R=yangguo@chromium.org

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24765 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Handle NaN value storing in Uint8Clamped typed arrays.

TEST=mjsunit/external-array
BUG=
R=dslomov@chromium.org

Review URL: https://codereview.chromium.org/667113002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24766 ce2b1a6d-e550-0410-aec6-3dcde31c8c00