Re: compilers using MMX instructions in the generated code

lindahl@pbm.com (Greg Lindahl)
19 Jan 2000 01:13:12 -0500

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Related articles
[4 earlier articles]
Re: compilers using MMX instructions in the generated code plakal@cs.wisc.edu (2000-01-09)
Re: compilers using MMX instructions in the generated code lindahl@pbm.com (2000-01-12)
Re: compilers using MMX instructions in the generated code olefevre@my-deja.com (2000-01-12)
Re: compilers using MMX instructions in the generated code mlross@jf.intel.com (2000-01-12)
Re: compilers using MMX instructions in the generated code andi@complang.tuwien.ac.at (2000-01-15)
Re: compilers using MMX instructions in the generated code bcombee@metrowerks.com (2000-01-19)
Re: compilers using MMX instructions in the generated code lindahl@pbm.com (2000-01-19)
Re: compilers using MMX instructions in the generated code a.richards@computer.org (Andrew Richards) (2000-01-23)
Re: compilers using MMX instructions in the generated code pica67@my-deja.com (Carsten Pitz) (2000-01-25)
Re: compilers using MMX instructions in the generated code andrew@bhjz.demon.co.uk (Andrew Richards) (2000-02-04)
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From: lindahl@pbm.com (Greg Lindahl)
Newsgroups: comp.compilers
Date: 19 Jan 2000 01:13:12 -0500
Organization: a guest of Shadow Island Games
References: 00-01-047
Keywords: code, optimize

andi@complang.tuwien.ac.at (Andreas Krall) writes:


> > In this example, I don't think you can vectorize both loops.
>
> It is possible to vectorize both loops. Our prototype compmiler for
> the SPARC VIS can handle this case (with a little bit support from the
> hardware). The SPARC has support for unaligned loads where only three
> instructions are necessary for an unaligned load


I was referring to vectorizing those loops on a proccessor like MMX,
which I believe requires 12-bit aligned loads, and has no support for
unaligned loads.


> Similar code can be emitted for processors without support by
> shifts and logical or.


However, you probably immediately revert to the same performance as
unvectorized on the MMX. But it would be worth analyzing.


-- g


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