On Sonntag, 14. April 2019 21:35:43 CEST wkitt...@windstream.net wrote: > On 4/14/19 7:28 AM, Rainer Stratmann wrote: > > On Samstag, 13. April 2019 22:30:55 CEST Alexey Tor. wrote: > >> E.g. i have a loop which test each s[i] char for several cases: 'a', > >> 'b', 'c'. > >> > >> for i:= 1 to length(s) do > >> > >> if (s[i]='a') or (s[i]='b') or (s[i]='c') then ... > >> > >> Can FPC optimize it so it only reads s[i] once (to register), not 3 > >> times? > > > > You can optimise by yourself. > > > > var > > > > c : char; > > l : longint; > > > > begin > > > > l := length( s ); > > for i := 1 to l do > > > > c := s[ i ]; > > if ( c = 'a' ) or ( c = 'b' ) or ( c = 'c' ) then ... > > this looks like it will read three times like the original instead of once > like using the IN set operation... it is still stepping through each one of > the comparison steps instead of just doing a set match...
It is at least better than reading s[ i ] at every compare operation. Feel free to make more optimizations if there is a chance. For example the IN operation. if c in ['a', 'b', 'c'] then ... You have to know the whole code to decide if it makes sense to drop the var c completely. _______________________________________________ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
