If the RHS is 0 and we have Smi feedback, speculate that the result (the LHS)
will continue to be in the Unsigned31 range.  This helps us avoid converting
the result to double when merging with Signed32.

R=jarin@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2709423002
Cr-Commit-Position: refs/heads/master@{#43415}

It has been turned on by default for a long time, and hydrogenized BinaryOpStubs actually depend on it being turned on.

BUG=v8:3487
LOG=n
R=ishell@chromium.org

Review URL: https://codereview.chromium.org/630023002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24415 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

The `right == 0` checks only worked for `0 <= right < 32`. This patch
replaces the checks with simple tests for negative results.

The attached test can detect this error, but the test relies on a broken
flag (--noopt-safe-uint32-operations), so it is skipped for now. See
issue 3487 for details.

BUG=
R=ulan@chromium.org

Review URL: https://codereview.chromium.org/487913005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23243 ce2b1a6d-e550-0410-aec6-3dcde31c8c00