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References: <9fef5273-8e1c-4d3e-9c62-790ae227103d@pixelhero.dev> <756C95B55C2DABF6755FCB63F332F045@eigenstate.org>
In-Reply-To: <756C95B55C2DABF6755FCB63F332F045@eigenstate.org>
From: Jonas Amoson <jonas.amoson@gmail.com>
Date: Mon, 18 Jan 2021 18:11:15 +0200
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Subject: Re: [9front] Weird >>= operator behaviour in 5c/5l
Reply-To: 9front@9front.org
Precedence: bulk

Left shifting by 32 instead of 0 does explain my
result, and seam indeed to be the real bug.

Regarding optimising out shifts where the number
of steps is zero: it already does that when using the
pattern x = x >> 0; but it doesn't for x >>= 0;

Thanks,
Jonas

On Mon, 18 Jan 2021 at 07:50, <ori@eigenstate.org> wrote:
>
> Quoth Noam Preil <noam@pixelhero.dev>:
> > It could just be architecture specific behavior.
> >
>
> It's a bug. Two, actually.
>
> 1) a shift of zero should be optimized out by
>    the compiler; cinap has a change for this in
>    the works already. This fix should hide the
>    second bug.
>
> 2) a shift by a literal zero is miscompiled by
>    the assembler into a shift by 32, because
>    of a missed special case in the instruction.
>    encoding. I'm working on fixing the assembler.