Support StringCharCodeAt in hydrogen/lithium.

Support StringCharCodeAt in hydrogen/lithium.

This patch adds H- and L-variants of StringCharCodeAt and StringLength.

StringCharCodeAt is used to inline a constant function call of
String.prototype.charCodeAt and to implement the corresponding inline
runtime function. It does not yet use the recently introduced extra IC
state. (We can specialize on string encoding and avoid deopts because
of out of bounds accesses.)

StringLength needs more work because the stub version of it also
supports strings wrappers and it matters in some cases. (We have to
separate the string only case.)

Committed: http://code.google.com/p/v8/source/detail?r=6408

[fschneider, 2011-01-19 16:23:44]

LGTM.

http://codereview.chromium.org/6243008/diff/3001/src/hydrogen.cc
File src/hydrogen.cc (right):

http://codereview.chromium.org/6243008/diff/3001/src/hydrogen.cc#newcode4156
src/hydrogen.cc:4156: if (!expr->target()->shared()->HasBuiltinFunctionId())
return false;
Maybe we don't need IsBuiltinMathFunction() anymore and can get rid of it.

http://codereview.chromium.org/6243008/diff/3001/src/ia32/lithium-ia32.h
File src/ia32/lithium-ia32.h (right):

http://codereview.chromium.org/6243008/diff/3001/src/ia32/lithium-ia32.h#newc...
src/ia32/lithium-ia32.h:1612: class LStringLength: public
LTemplateInstruction<1, 1> {
For consistency I'd write 

public LTemplateInstruction<1, 1, 0>

(Probably I should remove the default T=0 template parameter for the number of
temps.)

[Vitaly Repeshko, 2011-01-19 20:08:41]

http://codereview.chromium.org/6243008/diff/3001/src/hydrogen.cc
File src/hydrogen.cc (right):

http://codereview.chromium.org/6243008/diff/3001/src/hydrogen.cc#newcode4156
src/hydrogen.cc:4156: if (!expr->target()->shared()->HasBuiltinFunctionId())
return false;
On 2011/01/19 16:23:44, fschneider wrote:
> Maybe we don't need IsBuiltinMathFunction() anymore and can get rid of it.

Done.

http://codereview.chromium.org/6243008/diff/3001/src/ia32/lithium-ia32.h
File src/ia32/lithium-ia32.h (right):

http://codereview.chromium.org/6243008/diff/3001/src/ia32/lithium-ia32.h#newc...
src/ia32/lithium-ia32.h:1612: class LStringLength: public
LTemplateInstruction<1, 1> {
On 2011/01/19 16:23:44, fschneider wrote:
> For consistency I'd write 
> 
> public LTemplateInstruction<1, 1, 0>
> 
> (Probably I should remove the default T=0 template parameter for the number of
> temps.)
> 

Done.