Simple toplevel code generator support for short-circuited boolean OR...

Simple toplevel code generator support for short-circuited boolean OR
in a non-test (ie, value or effect) context.  (It is implicitly not in
a test context because the code generator does not support expressions
in a test context yet.)

Compilation is essentially the same as in the optimized code
generator.  The expression (e0 || e1) is compiled as if it were
(let (temp = e0) temp ? temp : e1).

On ia32 and x64 a single shared ToBoolean stub is used to convert a
value to a flag.  The inlined checks assumed by the stub are reordered
to compare to undefined (the common case in toplevel code?) first.  On
ARM a call to the runtime is used.  In the interest of code size no
checks are yet inlined on ARM.


Committed: http://code.google.com/p/v8/source/detail?r=3118

[William Hesse, 2009-10-23 07:20:04]

LGTM.

http://codereview.chromium.org/334006/diff/4001/5005
File src/x64/fast-codegen-x64.cc (right):

http://codereview.chromium.org/334006/diff/4001/5005#newcode515
Line 515: }
Should "Load a Location into rax and optionally the stack" be made into a macro?
 It looks like we will use it extensively.

[fschneider, 2009-10-23 08:41:37]

LGTM.

http://codereview.chromium.org/334006/diff/4001/5001
File src/ia32/fast-codegen-ia32.cc (right):

http://codereview.chromium.org/334006/diff/4001/5001#newcode518
Line 518: 
Idea: I don't know how relevant these expressions are for top-level code. But we
may want to consider not inlining all 5 checks here to conserve code size.