Speed up compares with characters ie single-character strings....

Speed up compares with characters ie single-character strings.
Make use of it when we know that something can't be a NaN.

Committed: http://code.google.com/p/v8/source/detail?r=3566

[Kasper Lund, 2010-01-08 07:25:37]

Comments:

http://codereview.chromium.org/524059/diff/1/11
File src/arm/codegen-arm.cc (right):

http://codereview.chromium.org/524059/diff/1/11#newcode4630
src/arm/codegen-arm.cc:4630: // special: (undefined == undefined) == true, but
(undefined <= undefined)
There seems to be a bunch of lines here that are too long.

http://codereview.chromium.org/524059/diff/1/7
File src/codegen.h (right):

http://codereview.chromium.org/524059/diff/1/7#newcode326
src/codegen.h:326: bool strict,
You now have to different fields that only makes sense when cc is eq. Have you
thought about combining them somehow?

http://codereview.chromium.org/524059/diff/1/5
File src/ia32/codegen-ia32.cc (right):

http://codereview.chromium.org/524059/diff/1/5#newcode1929
src/ia32/codegen-ia32.cc:1929: // If either side is a constant smi, optimize the
comparison.
Update comment. Consider rewriting the control flow to avoid too many of the
repeated checks (left_side.is_constant etc).

http://codereview.chromium.org/524059/diff/1/9
File src/objects.h (right):

http://codereview.chromium.org/524059/diff/1/9#newcode388
src/objects.h:388: const uint32_t kIsSymbolMask = 0x40;
Why did you change this? Do you need to update the comment above here (bit 6)?
Hmm.

http://codereview.chromium.org/524059/diff/1/8
File src/runtime.cc (right):

http://codereview.chromium.org/524059/diff/1/8#newcode5386
src/runtime.cc:5386: index_offset_(0), fast_elements_(fast_elements) { }
Conflict warning.

http://codereview.chromium.org/524059/diff/1/10
File src/x64/codegen-x64.cc (right):

http://codereview.chromium.org/524059/diff/1/10#newcode6282
src/x64/codegen-x64.cc:6282: // It is a heap number, so return non-equal if it's
NaN and equal if it's
Line too long.

http://codereview.chromium.org/524059/diff/1/10#newcode7752
src/x64/codegen-x64.cc:7752: return (static_cast<unsigned>(cc_) << 2) | (strict_
? 1 : 0) | nnn_value;
Maybe reorder to have cc | nnn | strict to make it clearer where the bits go?

http://codereview.chromium.org/524059/diff/1/2
File test/mjsunit/compare-character.js (right):

http://codereview.chromium.org/524059/diff/1/2#newcode31
test/mjsunit/compare-character.js:31: function conditionsMatch(a, b, c) {
Why do you have a separate function for this with poor parameter names? Why not
just call assertEquals?

http://codereview.chromium.org/524059/diff/1/4
File test/mjsunit/compare-nan.js (right):

http://codereview.chromium.org/524059/diff/1/4#newcode46
test/mjsunit/compare-nan.js:46: var b = ["NaN", "-1", "0", "1", "1.2", "-7.9",
"true", "false", "'foo'", "'0'", "'NaN'" ];
Line too long.

[Kasper Lund, 2010-01-08 09:31:34]

One more thing:

http://codereview.chromium.org/524059/diff/1/7
File src/codegen.h (right):

http://codereview.chromium.org/524059/diff/1/7#newcode320
src/codegen.h:320: enum NaNInformation { BothCouldBeNaN, CantBothBeNaN };
Split on multiple lines. Fix naming. Should be either BOTH_COULD_BE_NAN or
kBothCouldBeNaN.