Fix error introduced in version 3820

Fix error introduced in version 3820.  Add optimization suggested by the error.

Committed: http://code.google.com/p/v8/source/detail?r=3823

[William Hesse, 2010-02-09 13:17:27]

A one-line review.

[Kevin Millikin (Chromium), 2010-02-09 13:23:27]

LGTM, but can be simplified.

http://codereview.chromium.org/597006/diff/1/2
File src/ia32/stub-cache-ia32.cc (right):

http://codereview.chromium.org/597006/diff/1/2#newcode253
src/ia32/stub-cache-ia32.cc:253: __ mov(receiver, scratch2);
Why not:

__ mov(eax, FieldOperand(scratch2, String::kLengthOffset));
__ jmp(&tag_length);

and label the SmiTag(eax) with tag_length instead of using load_length?  (Or,
just duplicate the tag and return).

[William Hesse, 2010-02-09 13:49:37]

Suggestion taken, applied to all platforms.  ARM needed a change to make it safe
to pass the receiver in a register.

[Kevin Millikin (Chromium), 2010-02-09 14:17:08]

LGTM.

http://codereview.chromium.org/597006/diff/4008/3009
File src/arm/stub-cache-arm.cc (right):

http://codereview.chromium.org/597006/diff/4008/3009#newcode224
src/arm/stub-cache-arm.cc:224: Label check_string, check_wrapper;
check_string is a dead label?

http://codereview.chromium.org/597006/diff/4008/3009#newcode237
src/arm/stub-cache-arm.cc:237: // If arguments to LoadIC are passed in
registers, receiver must not be
Reword this comment or just get rid of it.

http://codereview.chromium.org/597006/diff/4008/3009#newcode245
src/arm/stub-cache-arm.cc:245: // Check if the object is a string.
No need for comment.

http://codereview.chromium.org/597006/diff/4008/3009#newcode247
src/arm/stub-cache-arm.cc:247: // Load length directly from the string.
No need for comment.