[fpc-pascal] Floating point question

[Florian Klämpfl]

> Am 04.02.2024 um 13:50 schrieb Adriaan van Os via fpc-pascal <fpc-pascal at lists.freepascal.org>:
> 
> Jonas Maebe via fpc-pascal wrote:
>> On 03/02/2024 18:42, James Richters via fpc-pascal wrote:
>>> Constants are also evaluated wrong,you don’t know what that constant is going to be used for, so all steps of evaluating a constant MUST be done in extended by the compiler, or the answer is just wrong.
>> See https://wiki.freepascal.org/User_Changes_2.2.0#Floating_point_constants and https://www.freepascal.org/daily/doc/prog/progsu19.html
> 
> I think this discussion shows that the 2.2 compiler change was a bad idea (for modes other than Delphi).

The result with the old code was that all floating point operations involving constants were carried out in full precision (normally double or extended) which is something unexpected and results in slow code.

Example:

const
  c2 = 2;
var
  s1, s2 : single;

…
s1:=s2/c2;

generated an expensive double division for no good reason.

OTOH:

const
  c2 : single = 2;
var
  s1, s2 : single;

…
s1:=s2/c2;

generated a single division.


 There is still the -CF option as a workaround to get the old behavior.