[MS] I ran the tclbench suite on tclsh compiled with three
different compilers and several optimisation combinations. This page
summarizes the results.

These tests were run on a PIII/600Mhz/192MB laptop running linux
RedHat7.2. 

The compilers were:
   * gcc2.96
   * gcc3.1  [http://gcc.gnu.org]
   * icc6.0  Intel C++ compiler for linux [http://www.intel.com/software/products/global/eval.htm] [Notes on compiling tcl with icc]

'''Results''' 
 
%|  SPEED  |SIZE    |COMPILER| OPTIONS |%                                
&|  1.00   | 1.00   |gcc2.96 |-O  -march=pentiumpro|&
&|  1.05   | 1.00   |gcc2.96 |-O  -march=pentiumpro -fomit-frame-pointer|&
&|  1.01   | 1.01   |gcc2.96 |-O2 -march=pentiumpro|&                     
&|  1.07   | 1.02   |gcc2.96 |-O2 -march=pentiumpro -fomit-frame-pointer|&
&|  1.01   | 0.97   |gcc2.96 |-Os -march=pentiumpro|&                     
&|  1.05   | 0.98   |gcc2.96 |-Os -march=pentiumpro -fomit-frame-pointer|&
&|  0.99   | 1.07   |gcc3.1  |-O  -march=pentium3|&                       
&|  1.03   | 1.08   |gcc3.1  |-O  -march=pentium3 -fomit-frame-pointer|&
&|  1.02   | 1.12   |gcc3.1  |-O2 -march=pentium3|&                     
&|  1.06   | 1.13   |gcc3.1  |-O2 -march=pentium3 -fomit-frame-pointer|&
&|  1.03   | 1.14   |gcc3.1  |-O3 -march=pentium3|&                     
&|  1.08   | 1.15   |gcc3.1  |-O3 -march=pentium3 -fomit-frame-pointer|&
&|  1.04   | 0.97   |gcc3.1  |-Os -march=pentium3|&                     
&|  1.06   | 0.97   |gcc3.1  |-Os -march=pentium3 -fomit-frame-pointer|&
&|  1.06   | 1.24   |icc6.0  |-O3 -xK|&                                 
&|  1.11   | 1.47   |icc6.0  |-O3 -xK -ip|&


'''Conclusions (?)'''
   * The "-fomit-frame-pointer" flag produces faster code with gcc. It is a question if it is worth the loss of a traceable core file - tcl shouldn't dump core
   * The default optimisation flag for gcc "-O" seems suboptimal; both GNU compilers produce faster and smaller code with "-Os"
   * The new gcc3.1 is not a big improvement on 2.96 for our purposes.
   * Intel's compiler with "-ip" produces slightly faster code than gcc (as measured by tclbench), but a much larger image. Otherwise, icc produces larger but not faster code.

'''Notes'''
   * These were all static builds of tclsh from the current (01-22-02) HEAD
   * The data presented is size/speed relative to the reference build "gcc2.96 -O". This produced a 702kB tclsh which ran the tclbench suite in 00:04:35.
   * All compilers were set to produce binaries exploiting the processors features ("-march" and "-x" flags). 
   * I have not checked for the intel equivalent to gcc's "-Os" flag.
   * The "-fomit-frame-pointer" flag to gcc produces code that is non-debuggable - the stack trace in core files is not usable. This behaviour is also present (I think) in the optimised code produced by icc.

[Brett Schwarz]
These links may be of interest as well:
http://www.coyotegulch.com/acovea/index.html
http://freshmeat.net/articles/view/730/


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