[PATCH] powerpc: provide __bswapdi2
David Woodhouse
dwmw2 at infradead.org
Mon May 13 20:38:13 EST 2013
On Mon, 2013-05-13 at 11:33 +0100, David Woodhouse wrote:
>
> On Mon, 2013-05-13 at 09:33 +0200, Gabriel Paubert wrote:
> > Actually, I'd swap the two mr instructions to never
> > have an instruction that uses the result from the
> > previous one.
>
> Bad GCC. No biscuit.
>
> Should we file a PR?
Maybe not. If you tell it to tune for an in-order machine like Cell, it
swaps them round. Although now I'm confused about which of POWER[567]
were in-order:
[dwmw2 at i7 ~]$ powerpc64-linux-gnu-gcc -O2 -S -o- bswapdi2.c -m32 | grep -B1 mr
rlwimi 11,3,24,16,23
mr 4,11
mr 3,10
[dwmw2 at i7 ~]$ powerpc64-linux-gnu-gcc -O2 -S -o- bswapdi2.c -m32 -mtune=cell | grep -B1 mr
rlwimi 11,3,24,16,23
mr 3,10
mr 4,11
[dwmw2 at i7 ~]$ powerpc64-linux-gnu-gcc -O2 -S -o- bswapdi2.c -m32 -mtune=power5 | grep -B1 mr
rlwimi 11,3,24,16,23
mr 3,10
mr 4,11
[dwmw2 at i7 ~]$ powerpc64-linux-gnu-gcc -O2 -S -o- bswapdi2.c -m32 -mtune=power6 | grep -B1 mr
rlwimi 11,3,24,16,23
mr 4,11
mr 3,10
[dwmw2 at i7 ~]$ powerpc64-linux-gnu-gcc -O2 -S -o- bswapdi2.c -m32 -mtune=power7 | grep -B1 mr
rlwimi 11,3,24,16,23
mr 4,11
mr 3,10
--
David Woodhouse Open Source Technology Centre
David.Woodhouse at intel.com Intel Corporation
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