[9] RFR (M): 8068038: C2: large constant offsets aren't handled on SPARC

[Vladimir Ivanov]

http://cr.openjdk.java.net/~vlivanov/8068038/webrev.00
https://bugs.openjdk.java.net/browse/JDK-8068038

C2 doesn't handle large constant offsets ((>=2^12 bytes) on SPARC and 
simply bails out the compilation and marks the method as non-compilable.

It has severe performance impact For example, some Octane benchmarks 
suffer >10x slowdown.

The fix is to use variable-sized encoding and put large offsets in the 
register. It means that all match rules and instructions which depend on 
emit_form3_mem_reg become variable-sized as well and their size should 
be computed dynamically.

I verified C2 compilation times and code emission still takes ~3-4%.

Also, did some cleanups: got rid of size computations in 
MachSpillCopyNode::implementation and helper methods, refactored 
printing logic.

Testing: octane, JPRT.

Thanks!

Best regards,
Vladimir Ivanov

PS: there's an additional cleanup [1] in sparc.ad (mostly 32-bit SPARC 
removal, but also added some comments). It can go along with this fix or 
as part of the 32-bit SPARC complete removal (JDK-8150388). Let me know 
what do you prefer.

[1] http://cr.openjdk.java.net/~vlivanov/8068038/webrev.cleanup