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softfloat: do not return pseudo-denormal from floatx80 remainder

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The floatx80 remainder implementation sometimes returns the numerator
unchanged when the denominator is sufficiently larger than the
numerator.  But if the value to be returned unchanged is a
pseudo-denormal, that is incorrect.  Fix it to normalize the numerator
in that case.

Signed-off-by: Joseph Myers <joseph@codesourcery.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <alpine.DEB.2.21.2006081655520.23637@digraph.polyomino.org.uk>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Joseph Myers 2020-06-08 16:56:20 +00:00 committed by Paolo Bonzini
parent 499a2f7b55
commit b662495dca
1 changed files with 19 additions and 3 deletions
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22
fpu/softfloat.c
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@ -5706,7 +5706,7 @@ floatx80 floatx80_modrem(floatx80 a, floatx80 b, bool mod,
float_status *status)
{
bool aSign, zSign;
int32_t aExp, bExp, expDiff;
int32_t aExp, bExp, expDiff, aExpOrig;
uint64_t aSig0, aSig1, bSig;
uint64_t q, term0, term1, alternateASig0, alternateASig1;
@ -5715,7 +5715,7 @@ floatx80 floatx80_modrem(floatx80 a, floatx80 b, bool mod,
return floatx80_default_nan(status);
}
aSig0 = extractFloatx80Frac( a );
aExp = extractFloatx80Exp( a );
aExpOrig = aExp = extractFloatx80Exp( a );
aSign = extractFloatx80Sign( a );
bSig = extractFloatx80Frac( b );
bExp = extractFloatx80Exp( b );
@ -5730,6 +5730,13 @@ floatx80 floatx80_modrem(floatx80 a, floatx80 b, bool mod,
if ((uint64_t)(bSig << 1)) {
return propagateFloatx80NaN(a, b, status);
}
if (aExp == 0 && aSig0 >> 63) {
/*
* Pseudo-denormal argument must be returned in normalized
* form.
*/
return packFloatx80(aSign, 1, aSig0);
}
return a;
}
if ( bExp == 0 ) {
@ -5749,7 +5756,16 @@ floatx80 floatx80_modrem(floatx80 a, floatx80 b, bool mod,
expDiff = aExp - bExp;
aSig1 = 0;
if ( expDiff < 0 ) {
if ( mod || expDiff < -1 ) return a;
if ( mod || expDiff < -1 ) {
if (aExp == 1 && aExpOrig == 0) {
/*
* Pseudo-denormal argument must be returned in
* normalized form.
*/
return packFloatx80(aSign, aExp, aSig0);
}
return a;
}
shift128Right( aSig0, 0, 1, &aSig0, &aSig1 );
expDiff = 0;
}