MIPS: Do the qNaN fixup at de-serialization time.

MIPS: Do the qNaN fixup at de-serialization time.

Too many edge cases trying to store mips qNaN pattern in ia32-generated
snapshot. Simpler to restore it on target, where it will always be correct.

This does unify the two NaN's that are currently stored in the Heap to the
single roots array NaN value.

BUG=
TEST=

[Erik Corry, 2012-04-17 08:21:15]

Is there a file missing from this CL?  I can't see where the NaN is being
quieted at deserialization time.  The line

NaN = %GetRootNaN;

is run in mksnapshot, not at deserialization time.

[Paul Lind, 2012-04-17 14:38:14]

It is line 1845 in isolate.cc:

if(des != NULL) Assembler::QuietNaN(heap_.nan_value());

Since the runtime NaN was changed to point to the roots-array NaN (and those are
the only two NaNs in the heap), we don't have to search for NaN's after
de-serialization, we can just fixup the roots-array NaN: heap_.nan_value().

[Erik Corry, 2012-04-20 14:55:25]

LGTM

https://chromiumcodereview.appspot.com/10093007/diff/1/src/isolate.cc
File src/isolate.cc (right):

https://chromiumcodereview.appspot.com/10093007/diff/1/src/isolate.cc#newcode...
src/isolate.cc:1846: if(des != NULL) Assembler::QuietNaN(heap_.nan_value());
Missing space after 'if'