[Linux-ia64] Re: strange performance behaviour with floats

Keith Owens
2003-02-24T02:01:10Z

On Sun, 23 Feb 2003 17:50:41 -0800,
David Mosberger <davidm@napali.hpl.hp.com> wrote:
>>>>>> On Mon, 24 Feb 2003 12:45:10 +1100, Keith Owens <kaos@sgi.com> said:
>
> Keith> generated a two bundle loop as you suggested, but BogoMIPS went down,
> Keith> not up.
>
>Note: 2 bundle != 2 cycle, but even ignoring that: what did you
>expect? BogoMIPS counts 2 instructions per loop iteration no matter
>how many instructions are being executed. Perhaps you can get the
>compiler to unroll the loop. Then you'd see a higher BogoMIPS.

Which loop needs unrolling? __delay generates

2d0: 11 00 00 00 01 00 [MIB] nop.m 0x0
2d6: 00 70 04 55 00 00 mov.i ar.lc=r14
2dc: 00 00 00 20 nop.b 0x0;;
2e0: 11 00 00 00 01 00 [MIB] nop.m 0x0
2e6: 00 00 00 02 00 a0 nop.i 0x0
2ec: 00 00 00 40 br.cloop.sptk.few 2e0 <calibrate_delay+0x100>;;

br.cloop is already a single bundle loop.