[gambit-list] Viewing CPS expansion?

D.McClain dbm at asyrmatos.com
Fri May 22 15:45:59 EDT 2009


Okay, you have my attention... let's see that isomorphism in  
practice. I have seen my own measurements, and invariably they  
produce code that is 30% slower for CPS form than direct form.  
Perhaps the compilers producing the actual native code have been  
tuned to look for common human idioms and not CPS traits?

Dr. David McClain
Sr. VP, Embedded Systems
Asyrmatos Inc.
Boston & Tucson
phone: 	520-529-2437
cell: 	520-390-3995
web: 	www.asyrmatos.com
e-mail:	dbm at asyrmatos.com




On May 22, 2009, at 12:38, Taylor R Campbell wrote:

>    Date: Fri, 22 May 2009 12:18:49 -0700
>    From: "D.McClain" <dbm at asyrmatos.com>
>
>    Very interesting... I would like to see your claims backed up by
>    actual measurements.
>
> How about an isomorphism between the set of direct-style Scheme
> programs and (a subset of) the set of CPS Scheme programs?  Then if
> you give me a compiler C, I can construct a compiler C' that uses a
> CPS intermediate representation and such that C(P) = C'(P) for any
> program P.  No measurement is necessary to observe that the code
> generated by C and C' is identical.
>
> Put another way, turning a program into CPS doesn't add to or remove
> from the information in a program.  So it doesn't make a compiler any
> more or less able to make assumptions about a program that enable it
> to generate better or worse code.  All it changes is how convenient it
> is to write the compiler.  It's just a way to lay out some data
> structures in the compiler.  If someone told you that a compiler
> turned programs into an XML-based intermediate representation, would
> you believe that person if he claimed that the use of XML caused the
> compiler to generate bad code?  (It might be indicative of incompetent
> software engineering on the part of the compiler's writers, but that's
> a different issue.)
>
>

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