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From Matthew French <matt...@camary.co.za>
Subject Re: Sending native code to the processor at runtime
Date Sat, 14 May 2005 21:59:31 GMT
On Fri, 2005-05-13 at 18:23 -0700, acoliver@apache.org wrote:
> Basically the compiler writes your machine code for you anyhow.  I'm 
> quite curious about the claims that it achieves 70% of native 
> performance (which is really quite good) in microbenchmarks.

Why can a JIT not achieve 110% of native performance? (Assuming that we
strip out the compile time and compare like with like.)

The reason I say 110% is that binary code is usually compiled for the
lowest common denominator. So x86 code targets a 386, and Sparc binaries
target UltraSparc v8 or older processors. 

The advantage a JIT has is that it knows exactly where it is being
compiled, so in theory can make use of as much hardware assistance as it
can.

Getting this right in practise will take a lot longer. Getting it right
across many platforms and processors - even more so.

- Matthew


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