[RFC][AArch64] Define TARGET_SPILL_CLASS

[Kugan <kugan dot vivekanandarajah at linaro dot org>]

Compiling some applications with -mgeneral-regs-only produces better
code (runs faster) compared to not using it. The difference here is that
when -mgeneral-regs-only is not used, floating point register are also
used in register allocation. Then IRA/LRA has to move them to core
registers before performing operations.

I experimented with TARGET_SPILL_CLASS (as in attached patch) to make
floating point register class as just spill class for integer pseudos.
Though this benefits the application which had this issue. Overall
performance with speck2k is neutral (some of the benchmarks benefits a
lot but others regress). I am looking to see if I can make it perform
better overall. Any suggestions welcome.

Attached experimental patch passes regression but 168.wupwise and
187.facerec miscompares now. I am looking at fixing this as well.

Thanks,
Kugan

gcc/
2014-05-22  Kugan Vivekanandarajah  <kuganv@linaro.org>

	* config/aarch64/aarch64.c (generic_regmove_cost) : Adjust GP2FP and
	FP2GP costs.
	(aarch64_spill_class) : New function.
	(TARGET_SHIFT_TRUNCATION_MASK) : Define.

Attachment: p.txt
Description: Text document