[fpc-devel] Improved compiler speed by 20%

[Sergei Gorelkin]

Peter Vreman wrote:
> 
> I gave the patch a quick try and the speed stays the same for compiling the compiler sources. Can
> you explain how you did measure the performance gain?
> 
First, I compiled the compiler using -gl switch in order to have 
procedure names in logs.
Then I compiled a project (it was my working copy of 
packages/fcl-xml/tests/xmlts.pp) using callgrind:

valgrind --tool=callgrind ppc386 -S2h -dRELEASE -gl xmlts.pp

Finally, annotated the log:

callgrind_annotate --tree=calling >file.txt

As a result, you get a file with call tree and execution times for most 
procedures. The numbers are very consistent across multiple runs.
I observed decrease in "Program totals" number (I actually don't know 
what it is - CPU instructions, ticks or something arbitrary): from
410,867,243 to 302,717,628.

I suspect that these numbers do not include time spent by kernel in disk 
i/o procedures, and that kernel time may be so high that it masks out 
all improvements. Also, I compiled a program with all used units already 
compiled, so in my case .ppu creation was not covered.
But anyway, smaller numbers should be better than bigger ones.

Sergei