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References: <20221106095106.849154-1-mailhol.vincent@wanadoo.fr> <20221106095106.849154-3-mailhol.vincent@wanadoo.fr>
In-Reply-To: <20221106095106.849154-3-mailhol.vincent@wanadoo.fr>
From: Nick Desaulniers <ndesaulniers@google.com>
Date: Thu, 10 Nov 2022 11:01:02 -0800
Message-ID: <CAKwvOdmN2==9tG0fxRO8K-eAJudeemaKUuhJEAuGHc=P8GpGwA@mail.gmail.com>
Subject: Re: [PATCH v1 2/2] x86/asm/bitops: Use __builtin_clz*() to evaluate
 constant expressions
To: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Cc: x86@kernel.org, Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, 
	Thomas Gleixner <tglx@linutronix.de>, linux-kernel@vger.kernel.org, 
	Yury Norov <yury.norov@gmail.com>, llvm@lists.linux.dev, Borislav Petkov <bp@suse.de>
Content-Type: text/plain; charset="UTF-8"

On Sun, Nov 6, 2022 at 1:51 AM Vincent Mailhol
<mailhol.vincent@wanadoo.fr> wrote:
>
>  #ifdef CONFIG_X86_64
> -static __always_inline int fls64(__u64 x)
> +static __always_inline int constant_fls64(u64 x)
> +{
> +       BUILD_BUG_ON(sizeof(unsigned long long) != sizeof(x));

Thanks for the patches! They LGTM; but why do we need this BUILD_BUG_ON here?

> +
> +       if (!x)
> +               return 0;
> +
> +       return BITS_PER_TYPE(x) - __builtin_clzll(x);
> +}

-- 
Thanks,
~Nick Desaulniers