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Re: [PATCH][AArch64] Implement new intrinsics vabsd_s64 and vnegd_s64



On 31/07/18 22:48, James Greenhalgh wrote:
On Fri, Jul 20, 2018 at 04:37:34AM -0500, Vlad Lazar wrote:
> Hi,
>
> The patch adds implementations for the NEON intrinsics vabsd_s64 and vnegd_s64.
> (https://developer.arm.com/products/architecture/cpu-architecture/a-profile/docs/ihi0073/latest/arm-neon-intrinsics-reference-architecture-specification)
>
> Bootstrapped and regtested on aarch64-none-linux-gnu and there are no regressions.
>
> OK for trunk?
>
> +__extension__ extern __inline int64_t
> +__attribute__ ((__always_inline__, __gnu_inline__, __artificial__))
> +vnegd_s64 (int64_t __a)
> +{
> +  return -__a;
> +}

Does this give the correct behaviour for the minimum value of int64_t? That
would be undefined behaviour in C, but well-defined under ACLE.


Similar intrinsics such as vneg_s8, vneg_s16 etc use the same implementation
(though on vector types) and the test in the testsuite for them (gcc.target/aarch64/vneg_s.c)
has cases for these limit values, so it seems to work there.
Does the fact that those are using vector types rather than the scalar int64_t matter?

Kyrill

Thanks,
James



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