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[ltsmaster] std.math: Fix frexp() for 128 bit reals by aligning EXPBI… #51

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Feb 20, 2018
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[ltsmaster] std.math: Fix frexp() for 128 bit reals by aligning EXPBI… #51

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19 changes: 9 additions & 10 deletions std/math.d
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Original file line number Diff line number Diff line change
Expand Up @@ -265,6 +265,7 @@ template floatTraits(T)
{
// EXPMASK is a ushort mask to select the exponent portion (without sign)
// EXPSHIFT is the number of bits the exponent is left-shifted by in its ushort
// EXPBIAS is the exponent bias - 1 (exp == EXPBIAS yields ×2^-1).
// EXPPOS_SHORT is the index of the exponent when represented as a ushort array.
// SIGNPOS_BYTE is the index of the sign when represented as a ubyte array.
// RECIP_EPSILON is the value such that (smallest_subnormal) * RECIP_EPSILON == T.min_normal
Expand Down Expand Up @@ -355,7 +356,7 @@ template floatTraits(T)
// Quadruple precision float
enum ushort EXPMASK = 0x7FFF;
enum ushort EXPSHIFT = 0;
enum ushort EXPBIAS = 0x3FFF;
enum ushort EXPBIAS = 0x3FFE;
enum realFormat = RealFormat.ieeeQuadruple;
version(LittleEndian)
{
Expand Down Expand Up @@ -2500,9 +2501,10 @@ T frexp(T)(const T value, out int exp) @trusted pure nothrow @nogc
if (ex) // If exponent is non-zero
{
if (ex == F.EXPMASK)
{ // infinity or NaN
{
// infinity or NaN
if (vl[MANTISSA_LSB] |
( vl[MANTISSA_MSB] & 0x0000_FFFF_FFFF_FFFF)) // NaN
(vl[MANTISSA_MSB] & 0x0000_FFFF_FFFF_FFFF)) // NaN
{
// convert NaNS to NaNQ
vl[MANTISSA_MSB] |= 0x0000_8000_0000_0000;
Expand All @@ -2512,17 +2514,15 @@ T frexp(T)(const T value, out int exp) @trusted pure nothrow @nogc
exp = int.min;
else // positive infinity
exp = int.max;

}
else
{
exp = ex - F.EXPBIAS;
vu[F.EXPPOS_SHORT] =
cast(ushort)((0x8000 & vu[F.EXPPOS_SHORT]) | 0x3FFE);
vu[F.EXPPOS_SHORT] = F.EXPBIAS | (0x8000 & vu[F.EXPPOS_SHORT]);
}
}
else if ((vl[MANTISSA_LSB]
|(vl[MANTISSA_MSB] & 0x0000_FFFF_FFFF_FFFF)) == 0)
else if ((vl[MANTISSA_LSB] |
(vl[MANTISSA_MSB] & 0x0000_FFFF_FFFF_FFFF)) == 0)
{
// vf is +-0.0
exp = 0;
Expand All @@ -2533,8 +2533,7 @@ T frexp(T)(const T value, out int exp) @trusted pure nothrow @nogc
vf *= F.RECIP_EPSILON;
ex = vu[F.EXPPOS_SHORT] & F.EXPMASK;
exp = ex - F.EXPBIAS - T.mant_dig + 1;
vu[F.EXPPOS_SHORT] =
cast(ushort)((0x8000 & vu[F.EXPPOS_SHORT]) | 0x3FFE);
vu[F.EXPPOS_SHORT] = F.EXPBIAS | (0x8000 & vu[F.EXPPOS_SHORT]);
}
return vf;
}
Expand Down