[aarch64-port-dev ] RFR: 8075930: AARCH64: Use FP Register in C2

[Edward Nevill]

Hi,

The aarch64 C2 compiler makes no use of the FP register even though this register is saved on entry and restored on exit and is therefore always available for allocation.

Recent testing on some micro benchmarks shows that this can have an adverse effect, both in terms of stack usage, and performance.

The following webrev allows C2 to use the FP register. 

http://cr.openjdk.java.net/~enevill/8075930/webrev/

I have run JTreg hotspot and langtools before and after this change with the following results:-

Before:-

hotspot: passed: 539, failed: 186, error: 87
langtools: passed: 3193, error: 33

After:-

hotspot: passed: 540, failed: 186: error: 86
langtools: passed: 3192, error: 34

Please review this change and if OK, push.

Thanks,
Ed.