Exclude the bit-field bits from string hash codes. String hash codes...

Exclude the bit-field bits from string hash codes.  String hash codes
are always odd if the bit-field bits are included.

Modified a couple of debugger tests that relied on the ordering of
elements in descriptor arrays.  Descriptor arrays are sorted by
hash-code values, so the order changes if we change the hash code.

Committed: http://code.google.com/p/v8/source/detail?r=440

[Kasper Lund, 2008-10-06 09:18:18]

LGTM, but I wouldn't change the hashing used in the megamorphic lookup table.
See comments:

http://codereview.chromium.org/6489/diff/27/231
File src/objects.h (right):

http://codereview.chromium.org/6489/diff/27/231#newcode2995
Line 2995: // Shift constants for retriving length and hash code from
retrieving

http://codereview.chromium.org/6489/diff/27/232
File src/stub-cache-arm.cc (right):

http://codereview.chromium.org/6489/diff/27/232#newcode107
Line 107: __ mov(scratch, Operand(scratch, LSR, String::kHashShift));
Is this really necessary? We mask off the lower bits anyway.

http://codereview.chromium.org/6489/diff/27/227
File src/stub-cache-ia32.cc (right):

http://codereview.chromium.org/6489/diff/27/227#newcode103
Line 103: __ shr(scratch, String::kHashShift);
I don't this is necessary here. The lower bits are masked off anyway, so it's
better not to do it.

http://codereview.chromium.org/6489/diff/27/236
File src/stub-cache.h (right):

http://codereview.chromium.org/6489/diff/27/236#newcode203
Line 203: uint32_t name_hash = name->Hash();
I prefer using the entire field here. We have to mask anyway so that's an easy
way to get rid of the lower bit.

[Mads Ager (chromium), 2008-10-06 09:35:34]

Good catch.  Fixed and submitted.