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softfloat: Add new flag for when denormal result is flushed to zero 

Add a new float_flag_output_denormal which is set when the result
of a floating point operation would be denormal but is flushed to
zero because we are in flush_to_zero mode. This is necessary because
some architectures signal this condition as an underflow and others
signal it as an inexact result.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
This commit is contained in:
Peter Maydell 2011-05-19 14:46:17 +01:00 committed by Aurelien Jarno
parent 43fe9bdb0f
commit e6afc87f80
2 changed files with 36 additions and 8 deletions
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41
fpu/softfloat.c
View File

@ -341,7 +341,10 @@ static float32 roundAndPackFloat32( flag zSign, int16 zExp, uint32_t zSig STATUS
return packFloat32( zSign, 0xFF, - ( roundIncrement == 0 ));
}
if ( zExp < 0 ) {
if ( STATUS(flush_to_zero) ) return packFloat32( zSign, 0, 0 );
if (STATUS(flush_to_zero)) {
float_raise(float_flag_output_denormal STATUS_VAR);
return packFloat32(zSign, 0, 0);
}
isTiny =
( STATUS(float_detect_tininess) == float_tininess_before_rounding )
|| ( zExp < -1 )
@ -520,7 +523,10 @@ static float64 roundAndPackFloat64( flag zSign, int16 zExp, uint64_t zSig STATUS
return packFloat64( zSign, 0x7FF, - ( roundIncrement == 0 ));
}
if ( zExp < 0 ) {
if ( STATUS(flush_to_zero) ) return packFloat64( zSign, 0, 0 );
if (STATUS(flush_to_zero)) {
float_raise(float_flag_output_denormal STATUS_VAR);
return packFloat64(zSign, 0, 0);
}
isTiny =
( STATUS(float_detect_tininess) == float_tininess_before_rounding )
|| ( zExp < -1 )
@ -699,7 +705,10 @@ static floatx80
goto overflow;
}
if ( zExp <= 0 ) {
if ( STATUS(flush_to_zero) ) return packFloatx80( zSign, 0, 0 );
if (STATUS(flush_to_zero)) {
float_raise(float_flag_output_denormal STATUS_VAR);
return packFloatx80(zSign, 0, 0);
}
isTiny =
( STATUS(float_detect_tininess) == float_tininess_before_rounding )
|| ( zExp < 0 )
@ -1030,7 +1039,10 @@ static float128
return packFloat128( zSign, 0x7FFF, 0, 0 );
}
if ( zExp < 0 ) {
if ( STATUS(flush_to_zero) ) return packFloat128( zSign, 0, 0, 0 );
if (STATUS(flush_to_zero)) {
float_raise(float_flag_output_denormal STATUS_VAR);
return packFloat128(zSign, 0, 0, 0);
}
isTiny =
( STATUS(float_detect_tininess) == float_tininess_before_rounding )
|| ( zExp < -1 )
@ -1761,7 +1773,12 @@ static float32 addFloat32Sigs( float32 a, float32 b, flag zSign STATUS_PARAM)
return a;
}
if ( aExp == 0 ) {
if ( STATUS(flush_to_zero) ) return packFloat32( zSign, 0, 0 );
if (STATUS(flush_to_zero)) {
if (aSig | bSig) {
float_raise(float_flag_output_denormal STATUS_VAR);
}
return packFloat32(zSign, 0, 0);
}
return packFloat32( zSign, 0, ( aSig + bSig )>>6 );
}
zSig = 0x40000000 + aSig + bSig;
@ -3120,7 +3137,12 @@ static float64 addFloat64Sigs( float64 a, float64 b, flag zSign STATUS_PARAM )
return a;
}
if ( aExp == 0 ) {
if ( STATUS(flush_to_zero) ) return packFloat64( zSign, 0, 0 );
if (STATUS(flush_to_zero)) {
if (aSig | bSig) {
float_raise(float_flag_output_denormal STATUS_VAR);
}
return packFloat64(zSign, 0, 0);
}
return packFloat64( zSign, 0, ( aSig + bSig )>>9 );
}
zSig = LIT64( 0x4000000000000000 ) + aSig + bSig;
@ -5282,7 +5304,12 @@ static float128 addFloat128Sigs( float128 a, float128 b, flag zSign STATUS_PARAM
}
add128( aSig0, aSig1, bSig0, bSig1, &zSig0, &zSig1 );
if ( aExp == 0 ) {
if ( STATUS(flush_to_zero) ) return packFloat128( zSign, 0, 0, 0 );
if (STATUS(flush_to_zero)) {
if (zSig0 | zSig1) {
float_raise(float_flag_output_denormal STATUS_VAR);
}
return packFloat128(zSign, 0, 0, 0);
}
return packFloat128( zSign, 0, zSig0, zSig1 );
}
zSig2 = 0;

3
fpu/softfloat.h
View File

@ -193,7 +193,8 @@ enum {
float_flag_overflow = 8,
float_flag_underflow = 16,
float_flag_inexact = 32,
float_flag_input_denormal = 64
float_flag_input_denormal = 64,
float_flag_output_denormal = 128
};
typedef struct float_status {