[fpc-devel] softfloat: sizeOf( floatx80 )

[Pierre Muller]

I think that the big endian version (see grep below)
would suffer if you would use packed
because the high field of size 2,
would put the low field of size 8 at offset 2,
which would trigger unaligned access to this field.

For the little endian definition,
it doesn't change anything, does it?

Pierre

See this grep result:

muller at cfarm187:~/pas/trunk/fpcsrc/rtl/inc$ grep -inA9 "floatx80 *=" *
softfpu.pp:139:  floatx80 = record
softfpu.pp-140-    case byte of
softfpu.pp-141-      // force the record to be aligned like a double
softfpu.pp-142-      // else *_to_double will fail for cpus like sparc
softfpu.pp-143-      // and avoid expensive unpacking/packing operations
softfpu.pp-144-      1: (dummy : extended);
softfpu.pp-145-      2: (low : qword;high : word);
softfpu.pp-146-  end;
softfpu.pp-147-
softfpu.pp-148-  float128 = record
--
softfpu.pp:167:  floatx80 = record
softfpu.pp-168-    case byte of
softfpu.pp-169-      // force the record to be aligned like a double
softfpu.pp-170-      // else *_to_double will fail for cpus like sparc
softfpu.pp-171-      // and avoid expensive unpacking/packing operations
softfpu.pp-172-      1: (dummy : qword);
softfpu.pp-173-      2: (high : word;low : qword);
softfpu.pp-174-  end;
softfpu.pp-175-
softfpu.pp-176-  float128 = record
--
ufloatx80.pp:32:      floatx80 = {$IFDEF FPC_DOTTEDUNITS}System.SoftFpuX80{$ELSE}sfpux80{$ENDIF}.floatx80;
ufloatx80.pp-33-


Le 27/09/2024 à 20:00, Martin Frb via fpc-devel a écrit :
> Is there any indention in
> 
>     floatx80 = record
>       case byte of
>         1: (low : qword;high : word);
>         // force the record to be aligned like a double
>         // else *_to_double will fail for cpus like sparc
>         // and avoid expensive unpacking/packing operations
>         2: (dummy : extended);
>     end;
> 
> 
> NOT being a packed record?
> 
> If it was packed, it should have the same size as an actual extended: 80
> bits / 10 bytes.
> 
> Possible similar issues for other softfloat types
> _______________________________________________
> fpc-devel maillist  -  fpc-devel at lists.freepascal.org
> https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel