Fix the hole loading optimization.

Fix the hole loading optimization.
- Holes are only ever loaded as double or tagged.
- Change to tagged has to deoptimize on undefined (no implicit
  conversions from double the hole NaN -> tagged undefined).

BUG=
R=jkummerow@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=14829

[Toon Verwaest, 2013-05-27 15:16:09]

PTAL

[Jakob Kummerow, 2013-05-27 16:03:05]

LGTM with a comment that applies to all architectures.

Also, how about a regression test for the issue(s) that this patch fixes?

https://chromiumcodereview.appspot.com/16099006/diff/1/src/ia32/lithium-codeg...
File src/ia32/lithium-codegen-ia32.cc (right):

https://chromiumcodereview.appspot.com/16099006/diff/1/src/ia32/lithium-codeg...
src/ia32/lithium-codegen-ia32.cc:5102: __ bind(&hole);
nit: "hole" is a misleading name when it handles undefined too. Please call the
label "hole_or_undefined" or "convert" or something like that.

[Toon Verwaest, 2013-05-27 17:33:05]

Addressed comments, landing.

[Toon Verwaest, 2013-05-27 17:33:23]

Committed patchset #2 manually as r14829 (presubmit successful).