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Re: [Patch, Darwin, I386] enable mtune=core2 on darwin and make it the default.

On 13 Aug 2010, at 20:25, Jack Howarth wrote:

On Fri, Aug 13, 2010 at 06:36:12PM +0100, IainS wrote:
Hi HJ,

On 13 Aug 2010, at 18:22, H.J. Lu wrote:

On Fri, Aug 13, 2010 at 9:39 AM, IainS
<> wrote:
In order to do that it was necessary to get -mtune=core2 to work ..
... this had a couple of residual cases where the use of movq is
incompatible with the darwin  assembler.

Do you know -mtune=core generates slower code than -mtune=generic?

I have not benchmarked - unfortunately, we volunteers do not have access
to SPEC &c.

I can repeat the benchmarks this weekend but the last time I looked
at the performance of the Polyhedron 2005 benchmarks on x86_64-apple- darwin10,
I found -mtune=core2 was slower than -mtune=generic.

Do you have any reasonable body of c/c++ benchmarks? I have the Polyhedron fortran ones.

Odd that the vendor would choose that default if it's genuinely less performance...
I guess I could look and see if there are changed tuning params...

... anyway I'm not going to nail colors to the mast over this one - it's easily changed.

... remember the old BYTE article "Lies, Damned Lies & Benchmarks" ?



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