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@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@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@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@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@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.woodho...@intel.com Intel Corporation
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