[plt-scheme] 301.4

From: Hans Oesterholt-Dijkema (hdnews at gawab.com)
Date: Wed Feb 1 14:35:53 EST 2006

GNU Lightning uses a RISC instruction set. This could be
hard to optimize for a CISC architecture. Could it be that
this is a cause of the small speed gain?


Jim Blandy schreef:
> On 1/30/06, Matthew Flatt <mflatt at cs.utah.edu> wrote:
>> For now, typical speedups from JIT compilation are in the range 1x
>> (i.e., no speedup) to 1.3x, with an occasional 2x or 4x. The JIT rarely
>> slows any program --- though, of course, it's possible.
> Are you comparing the JIT to mzc, or to the bytecode interpreter?
> If the interpreter, I'm surprised.  are there bytecodes for which you
> emit slower code than the interpreter path for that bytecode?  Or does
> a lowered instruction cache hit rate eat your gains?
> Don't get me wrong --- this is a great hack.  But for goodness' sake,
> why would one plunge into the hair and non-portability of native code
> generation if one doesn't get a nice hefty speed boost from it?  That
> is, why isn't the bytecode interpreter a sufficient stopgap until the
> "real thing" is ready?
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