d0p1/ack
1
0
Fork 0
Code Issues Pull requests Packages Projects Releases Wiki Activity

another fix for printf(float) on m68k platform

Browse source 
bug caused by this instruction:

  fmove.l fp0,d0 

problem was caused by a conflict between the fpu emulator (softfloat) and the compiler.

the emulator implemented this as a purely arithmetic move & conversion,
but the compiler assumed that the result could be interpreted as a logical (ie unsigned) conversion.
rightly or wrongly.


for example, if fp0 contained the value 2576980377.0  which is unsigned integer -1717987328
the emulator would treat this as an integer overflow and move 0x7fffffff (INT_MAX) into d0.

The complier on the other hand would assume that d0 contained 2576980377 (the unsigned value).

I don't know which is correct, but this is my fix for the time being.
This commit is contained in:
tevorbl 2020-06-02 13:00:03 +01:00
parent 04fe0aa53e
commit 6fe335b9e9
1 changed files with 4 additions and 4 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

8
plat/linux68k/emu/musashi/softfloat/softfloat.c
View file

@ -95,7 +95,7 @@ static int32 roundAndPackInt32( flag zSign, bits64 absZ )
if ( zSign ) z = - z; if ( zSign ) z = - z;
if ( ( absZ>>32 ) || ( z && ( ( z < 0 ) ^ zSign ) ) ) { if ( ( absZ>>32 ) || ( z && ( ( z < 0 ) ^ zSign ) ) ) {
float_raise( float_flag_invalid ); float_raise( float_flag_invalid );
return zSign ? (sbits32) 0x80000000 : 0x7FFFFFFF; return z /* zSign ? (sbits32) 0x80000000 : 0x7FFFFFFF*/;
} }
if ( roundBits ) float_exception_flags |= float_flag_inexact; if ( roundBits ) float_exception_flags |= float_flag_inexact;
return z; return z;
@ -146,9 +146,9 @@ static int64 roundAndPackInt64( flag zSign, bits64 absZ0, bits64 absZ1 )
if ( z && ( ( z < 0 ) ^ zSign ) ) { if ( z && ( ( z < 0 ) ^ zSign ) ) {
overflow: overflow:
float_raise( float_flag_invalid ); float_raise( float_flag_invalid );
return return z
zSign ? (sbits64) LIT64( 0x8000000000000000 ) /* zSign ? (sbits64) LIT64( 0x8000000000000000 )
: (sbits64)( 0x7FFFFFFFFFFFFFFF ); : (sbits64)( 0x7FFFFFFFFFFFFFFF )*/;
} }
if ( absZ1 ) float_exception_flags |= float_flag_inexact; if ( absZ1 ) float_exception_flags |= float_flag_inexact;
return z; return z;