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softfloat: add float128_is_{normal,denormal}

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Needed on s390x, to test for the data class of a number. So it will
gain soon a user.

A number is considered normal if the exponent is neither 0 nor all 1's.
That can be checked by adding 1 to the exponent, and comparing against
>= 2 after dropping an eventual overflow into the sign bit.

While at it, convert the other floatXX_is_normal functions to use a
similar, less error prone calculation, as suggested by Richard H.

Backports commit 47393181604d507f4fe2a15a65b1eede0f974d6a from qemu
This commit is contained in:
David Hildenbrand 2019-02-28 15:11:39 -05:00 committed by Lioncash
parent b9da32241b
commit 24a2bd702c
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GPG key ID: 4E3C3CC1031BA9C7
1 changed files with 12 additions and 2 deletions
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14
qemu/include/fpu/softfloat.h
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@ -471,7 +471,7 @@ static inline int float32_is_zero_or_denormal(float32 a)
static inline bool float32_is_normal(float32 a)
{
return ((float32_val(a) + 0x00800000) & 0x7fffffff) >= 0x01000000;
return (((float32_val(a) >> 23) + 1) & 0xff) >= 2;
}
static inline bool float32_is_denormal(float32 a)
@ -628,7 +628,7 @@ static inline int float64_is_zero_or_denormal(float64 a)
static inline bool float64_is_normal(float64 a)
{
return ((float64_val(a) + (1ULL << 52)) & -1ULL >> 1) >= 1ULL << 53;
return (((float64_val(a) >> 52) + 1) & 0x7ff) >= 2;
}
static inline bool float64_is_denormal(float64 a)
@ -948,6 +948,16 @@ static inline int float128_is_zero_or_denormal(float128 a)
return (a.high & 0x7fff000000000000LL) == 0;
}
static inline bool float128_is_normal(float128 a)
{
return (((a.high >> 48) + 1) & 0x7fff) >= 2;
}
static inline bool float128_is_denormal(float128 a)
{
return float128_is_zero_or_denormal(a) && !float128_is_zero(a);
}
static inline int float128_is_any_nan(float128 a)
{
return ((a.high >> 48) & 0x7fff) == 0x7fff &&