[AArch64] Make more use of function_abi

[AArch64] Make more use of function_abi

This patch makes more use of the function_abi infrastructure.
We can then avoid checking specifically for the vector PCS in
a few places, and can test it more directly otherwise.

Specifically: we no longer need to call df_set_regs_ever_live
for the extra call-saved registers, since IRA now does that for us.
We also don't need to handle the vector PCS specially in
aarch64_epilogue_uses, because DF now marks the registers
as live on exit.

2019-09-30  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* config/aarch64/aarch64.c (aarch64_layout_frame): Use crtl->abi
	to test whether we're compiling a vector PCS function and to test
	whether the function needs to save a particular register.
	Remove the vector PCS handling of df_set_regs_ever_live.
	(aarch64_components_for_bb): Use crtl->abi to test whether
	the function needs to save a particular register.
	(aarch64_process_components): Use crtl->abi to test whether
	we're compiling a vector PCS function.
	(aarch64_expand_prologue, aarch64_expand_epilogue): Likewise.
	(aarch64_epilogue_uses): Remove handling of vector PCS functions.

From-SVN: r276341