Re: [PATCH] powerpc: POWER7 optimised memcpy using VMX and enhanced prefetch

On Dec 17, 2012, at 5:33 AM, Anton Blanchard [off-list ref] wrote:

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Hi Jimi,
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quoted

I know this is a little late, but shouldn't these power7 specific
thingies be in "obj-$(CONFIG_PPC_BOOK3S_64)". The reason I ask is
that my compiler pukes on "dcbtst" and as I deal with that I wanted
to point this out.

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I guess we could do that.

I think it is the right idea since it is unclear that your optimizations =
would actually help an embedded system where most of these cache =
prefetches are NOPs and only wait decode/dispatch cycles.

It's a bit strange your assembler is
complaining about the dcbtst instructions since we wrap them with
power4:

Not really, the binutils is a little old (RHEL 6.2), unfortunately it =
_is_ the toolchain most people are using at the moment.
It will take me a while to get everyone using newer ones since most are =
scientists using the packages they get.

My suggestion was really for correctness,  My current patches for BG/Q =
introduce a macro replacement.
-jx

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.machine push
.machine "power4"
       dcbt    r0,r4,0b01000
       dcbt    r0,r7,0b01010
       dcbtst  r0,r9,0b01000
       dcbtst  r0,r10,0b01010
       eieio
       dcbt    r0,r8,0b01010   /* GO */
.machine pop
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Anton