MIPS: Reverted the number of deopt entries to 4096.

MIPS: Reverted the number of deopt entries to 4096.

On MIPS we cannot double the number of deoptimization entries easily
because the generated code would contain long branches (>128K) and we use
BlockTrampolinePoolScope in the Deoptimizer::TableEntryGenerator::GeneratePrologue method.
Also, we cannot use the Jr instruction here because the Deoptimizer::CreateCode method asserts
that the generated code does not contain reloc information.

BUG=
TEST=
Patch from Daniel Kalmar.
Committed: http://code.google.com/p/v8/source/detail?r=10514

[kalmard, 2012-01-26 11:14:27]

We noticed that you changed the deoptimization table size to 8k. Unfortunately
this change causes problems on MIPS, because this way the table becomes larger
than the maximum possible direct jump offset. We see no regressions if we change
this value back to the original 4k for the MIPS architecture. Could you please
explain why this change was made, and whether you think it would be OK to keep
using the old 4k size for 3.8? We are prepared to make changes to this system
for future releases, but we feel that for the upcoming 3.8 release it is
probably better to just use the old, proven method, as long as it doesn't cause
any problems.

[Sven Panne, 2012-01-26 11:55:02]

The reason for this change was that Mandreel-generated JavaScript leads to a
huge number of deoptimization entries. If we do not increase the limit, we bail
out and do not use Crankshaft for performance-critical stuff, which is very bad.
Note that we have some Mandreel code which even needs 16k entries.

I don't know if we should revert this for 3.8 or not, I just wanted to explain
the motivation behind this change.

[fschneider, 2012-01-26 15:33:40]

lgtm

http://codereview.chromium.org/9169079/diff/1/src/deoptimizer.h
File src/deoptimizer.h (right):

http://codereview.chromium.org/9169079/diff/1/src/deoptimizer.h#newcode271
src/deoptimizer.h:271: static const int kNumberOfEntries = 4096;
Maybe add a comment to why the size is smaller on MIPS.