svn commit: r187251 - head/sys/mips/malta
sobomax at FreeBSD.org
Thu Jan 15 15:14:23 PST 2009
Christoph Mallon wrote:
> Alexey Dokuchaev schrieb:
>> On Wed, Jan 14, 2009 at 07:05:27PM -0700, M. Warner Losh wrote:
>>> In message: <20090115020752.52566769.stas at FreeBSD.org>
>>> Stanislav Sedov <stas at FreeBSD.org> writes:
>>> : > + shift = 8 * (reg & 3);
>>> : > : : Would it make sense to replace this with
>>> : > + shift = (reg & 3) << 3;
>>> : : to not rely on possible compiler optimizations?
>>> I don't think that it matters all that much these days...
>> But the name "shift" kinda suggests << instead of *, no?
> The value *is* a shift amount (see its uses a few lines down). Its name
> does not imply the way it is calculated, but what it is used for.
> BTW: Even the most cheap compilers emit shift instructions for
> multiplication by a power of two. The new code also is clearly faster
> then the old - quite some code gets generated for switches.
I believe Warner's point is that the code is not in the hot path, so
that it should not really matter either way.
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