[fpc-devel] certain divisions in single precision only

Florian Klämpfl florian at freepascal.org
Sun Dec 8 18:41:20 CET 2019

Am 08.12.19 um 18:17 schrieb Martok:
>> Indeed, this is by design. See
>> https://wiki.freepascal.org/User_Changes_2.2.0#Floating_point_constants for
>> how to explicitly specify a different precision.
> That was long before the change Tomas discovered.
> The gotcha here is about your fix to
> <https://bugs.freepascal.org/view.php?id=25121>, which together with the one you
> linked made runtime and compile time evaluation the same, at the expense of
> specifically breaking Delphi compat.
>  From the current Delphi Reference:
>> In Delphi, intermediate results of Single precision floating-point
>> expressions are always implicitly stored as Extended on x86.
>> By default, all x64 arithmetic operations and expressions involving only
>> Single precision floating-point values retain high precision by storing
>> intermediate results as Double precision values.
> But since then, FPC sees Single / Int2Single = Single, with no high precision
> intermediates.

As the delphi behavior is very i386/x86-64 specific, FPC deviates from 
it (not to mention that the non-i386 behavior was implemented years 
before a non-i386 delphi was available).

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