[fpc-pascal] Can FPC optimize: if (s[i]='a') or ...

[wkitty42 at windstream.net]

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...


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