[x265] [PATCH] fix invalid Instruction Set provided in CLI if CPU doesn't support it

[Steve Borho]

On 10/28, dnyaneshwar at multicorewareinc.com wrote:
> # HG changeset patch
> # User Dnyaneshwar G <dnyaneshwar at multicorewareinc.com>
> # Date 1446021877 -19800
> #      Wed Oct 28 14:14:37 2015 +0530
> # Node ID 975087370d14e90cd63edecb34fb4bf2feda2468
> # Parent  6563218ce342c30bfd4f9bc172a1dab510e6e55b
> fix invalid Instruction Set provided in CLI if CPU doesn't support it
> 
> This patch avoids crash/invalid instructions when we provide instruction sets to
> be used are higher than the cpu capabilities.
> 
> For example, if our cpu supports instruction sets upto AVX and we provide
> --asm "avx2" (AVX2 is higher than AVX) then it will show warning and use default
> x265 detected intruction sets.

The whole point of having this override is in case our CPU detection is
somehow wrong. The user needs to be able to override the detection mask.

That said.. if the user provided mask has bits set that were not
detected, it's ok to log a serious warning that says you think the
encoder is about to break and it is the user's fault.

BTW: this feature is often used for benchmarking, to disable certain
optimizations piecemeal, but that is not the primary reason why it
exists.

> diff -r 6563218ce342 -r 975087370d14 source/common/primitives.cpp
> --- a/source/common/primitives.cpp	Mon Oct 26 12:13:53 2015 +0530
> +++ b/source/common/primitives.cpp	Wed Oct 28 14:14:37 2015 +0530
> @@ -238,6 +238,15 @@
>              primitives.cu[i].intra_pred_allangs = NULL;
>  
>  #if ENABLE_ASSEMBLY
> +
> +        if ((uint32_t)param->cpuid > X265_NS::cpu_detect())
> +        {
> +            if (param->logLevel >= X265_LOG_INFO)
> +                x265_log(param, X265_LOG_WARNING, "Unsupported CPUID provided in CLI, so choosing x265 detected CPUID!\n");
> +
> +            param->cpuid = X265_NS::cpu_detect();
> +        }
> +
>          setupInstrinsicPrimitives(primitives, param->cpuid);
>          setupAssemblyPrimitives(primitives, param->cpuid);
>  #endif
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-- 
Steve Borho