Hi All,

This patch implements the ACLE hint intrinsics (nop, yield, wfe, wfi, 
sev and sevl), for AArch64.

The instructions are documented in the ArmARM[1] and the intrinsics 
specification will be
published on the Arm website [2].

[1] 
https://developer.arm.com/docs/ddi0487/latest/arm-architecture-reference-manual-armv8-for-armv8-a-architecture-profile
[2] 
http://infocenter.arm.com/help/topic/com.arm.doc.ihi0053c/IHI0053C_acle_2_0.pdf

Bootstrapped on aarch64-none-linux-gnu and regression tested on 
aarch64-none-elf with no regressions.

Ok for trunk? If ok, could someone commit the patch on my behalf, I 
don't have commit rights.

Thanks,
Srinath

gcc/ChangeLog:

2019-01-10  Srinath Parvathaneni  <srinath.parvathaneni@arm.com>

	* config/aarch64/aarch64.md (yield): New pattern name.
	(wfe): Likewise.
	(wfi): Likewise.
	(sev): Likewise.
	(sevl): Likewise.
	(UNSPECV_YIELD): New volatile unspec.
	(UNSPECV_WFE): Likewise.
	(UNSPECV_WFI): Likewise.
	(UNSPECV_SEV): Likewise.
	(UNSPECV_SEVL): Likewise.
	* config/aarch64/aarch64-builtins.c (aarch64_builtins):
	AARCH64_SYSHINTOP_BUILTIN_NOP: New builtin.
	AARCH64_SYSHINTOP_BUILTIN_YIELD: Likewise.
	AARCH64_SYSHINTOP_BUILTIN_WFE: Likewise.
	AARCH64_SYSHINTOP_BUILTIN_WFI: Likewise.
	AARCH64_SYSHINTOP_BUILTIN_SEV: Likewise.
	AARCH64_SYSHINTOP_BUILTIN_SEVL: Likewise.
	(aarch64_init_syshintop_builtins): New function.
	(aarch64_init_builtins): New call statement.
	(aarch64_expand_builtin): New case.
	* config/aarch64/arm_acle.h (__nop ): New inline function.
	(__yield): Likewise.
	(__sev): Likewise.
	(__sevl): Likewise.
	(__wfi): Likewise.
	(__wfe): Likewise.

gcc/testsuite/ChangeLog:

2019-01-10  Srinath Parvathaneni  <srinath.parvathaneni@arm.com>

	* gcc.target/aarch64/acle/hint-1.c: New test.
	* gcc.target/aarch64/acle/hint-2.c: Likewise.