On Wed, May 29, 2019 at 03:48:29PM +0100, Srinath Parvathaneni wrote:
> Hi All,
>
> This patch implements the __yield(), __wfe(), __wfi(), __sev() and
> __sevl() ACLE (hint) intrinsics for AArch64 as yield, wfe, wfi, sev and
> sevl (hint) instructions respectively.
>
> The instructions are documented in the ArmARM[1] and the intrinsics
> specification are 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]
> https://developer.arm.com/docs/ihi0053/latest/arm-c-language-extensions-21-architecture-specification
>
> Bootstrapped on aarch64-none-linux-gnu and regression tested on
> aarch64-none-elf with no regressions.
>
> Ok for trunk? If ok, could someone please commit the patch on my behalf,
> I don't have commit rights.
I can't tell from the documentation, is this the expected behaviour?
$ cat yield.c
#include "arm_acle.h"
int foo (int* counter)
{
*counter = 5;
__yield();
*counter = 5;
__yield();
*counter = 5;
__yield();
*counter = 5;
__yield();
}
$ gcc -O2 yield.c
foo:
mov w1, 5
str w1, [x0]
yield
yield
yield
yield
ret
i.e. should we expect the memory writes to be considered dead and eliminated,
or should they live over the __yield.
I have similar questions as to whether GCC's unspec_volatile actually
implements the required semantics from the ACLE.
Thanks,
James
>
> Thanks,
> Srinath
>
> gcc/ChangeLog:
>
> 2019-05-29 Srinath Parvathaneni <srinath.parvathan...@arm.com>
>
> * config/aarch64/aarch64.md (UNSPECV_YIELD): New volatile unspec.
> (UNSPECV_WFE): Likewise.
> (UNSPECV_WFI): Likewise.
> (UNSPECV_SEV): Likewise.
> (UNSPECV_SEVL): Likewise.
> (yield): New pattern name.
> (wfe): Likewise.
> (wfi): Likewise.
> (sev): Likewise.
> (sevl): Likewise.
> * config/aarch64/aarch64-builtins.c (aarch64_builtins):
> AARCH64_BUILTIN_YIELD: New builtin.
> AARCH64_BUILTIN_WFE: Likewise.
> AARCH64_BUILTIN_WFI: Likewise.
> AARCH64_BUILTIN_SEV: Likewise.
> AARCH64_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 (__yield): New inline function.
> (__sev): Likewise.
> (__sevl): Likewise.
> (__wfi): Likewise.
> (__wfe): Likewise.
>
> gcc/testsuite/ChangeLog:
>
> 2019-05-29 Srinath Parvathaneni <srinath.parvathan...@arm.com>
>
> * gcc.target/aarch64/acle/hint-1.c: New test.
>
