[VM] Should probably add -fno-gcse to the GCC flags

Ned Konz ned at bike-nomad.com
Wed Aug 6 19:52:03 UTC 2003


The GCC manual recommends trying the -fno-gcse (omit global common 
subexpression extraction) flag when you're using the computed gotos. 
Since we're doing this in the gnuified interpreters, I figured I'd 
try it.

So I just recompiled the one file (gnu-interp.c) with the -fno-gcse 
option added to the
	-O2 -fomit-frame-pointer

options that were already there.

Here's the results:

0 tinyBenchmarks 

with -fno-gcse in gnu-interp
 '114081996 bytecodes/sec; 4165025 sends/sec'
 '115315315 bytecodes/sec; 4086882 sends/sec'
  '113374667 bytecodes/sec; 4177005 sends/sec'

without -fno-gcse in gnu-interp
 '114081996 bytecodes/sec; 3942639 sends/sec'
'115315315 bytecodes/sec; 3996896 sends/sec'
'112775330 bytecodes/sec; 3942639 sends/sec'

As you can see, there are small but measurable differences in speed.

This is on an AMD Duron processor, under Linux, with the SourceForge 
VM sources.

-- 
Ned Konz
http://bike-nomad.com
GPG key ID: BEEA7EFE



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