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fpu/softfloat: Define floatN_default_nan in terms of parts_default_nan

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Isolate the target-specific choice to 2 functions instead of 6.

The code in float16_default_nan was only correct for ARM, MIPS, and X86.
Though float16 support is rare among our targets.

The code in float128_default_nan was arguably wrong for Sparc. While
QEMU supports the Sparc 128-bit insns, no real cpu enables it.

The code in floatx80_default_nan tried to be over-general. There are
only two targets that support this format: x86 and m68k. Thus there
is no point in inventing a value for snan_bit_is_one.

Move routines that no longer have ifdefs out of softfloat-specialize.h.

Backports commit 0218a16e540ad416683e19dfbd52f75092507b27 from qemu
This commit is contained in:
Richard Henderson 2018-05-20 00:04:18 -04:00 committed by Lioncash
parent 77bee9e8a5
commit df3436b518
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GPG key ID: 4E3C3CC1031BA9C7
2 changed files with 47 additions and 99 deletions
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105
qemu/fpu/softfloat-specialize.h
View file

@ -179,94 +179,22 @@ static FloatParts parts_silence_nan(FloatParts a, float_status *status)
return a;
}
/*----------------------------------------------------------------------------
| The pattern for a default generated half-precision NaN.
*----------------------------------------------------------------------------*/
float16 float16_default_nan(float_status *status)
{
#if defined(TARGET_ARM)
return const_float16(0x7E00);
#else
if (snan_bit_is_one(status)) {
return const_float16(0x7DFF);
} else {
#if defined(TARGET_MIPS)
return const_float16(0x7E00);
#else
return const_float16(0xFE00);
#endif
}
#endif
}
/*----------------------------------------------------------------------------
| The pattern for a default generated single-precision NaN.
*----------------------------------------------------------------------------*/
float32 float32_default_nan(float_status *status)
{
#if defined(TARGET_SPARC) || defined(TARGET_M68K)
return const_float32(0x7FFFFFFF);
#elif defined(TARGET_PPC) || defined(TARGET_ARM) || defined(TARGET_ALPHA) || \
defined(TARGET_XTENSA) || defined(TARGET_S390X) || \
defined(TARGET_TRICORE) || defined(TARGET_RISCV)
return const_float32(0x7FC00000);
#elif defined(TARGET_HPPA)
return const_float32(0x7FA00000);
#else
if (snan_bit_is_one(status)) {
return const_float32(0x7FBFFFFF);
} else {
#if defined(TARGET_MIPS)
return const_float32(0x7FC00000);
#else
return const_float32(0xFFC00000);
#endif
}
#endif
}
/*----------------------------------------------------------------------------
| The pattern for a default generated double-precision NaN.
*----------------------------------------------------------------------------*/
float64 float64_default_nan(float_status *status)
{
#if defined(TARGET_SPARC) || defined(TARGET_M68K)
return const_float64(LIT64(0x7FFFFFFFFFFFFFFF));
#elif defined(TARGET_PPC) || defined(TARGET_ARM) || defined(TARGET_ALPHA) || \
defined(TARGET_S390X) || defined(TARGET_RISCV)
return const_float64(LIT64(0x7FF8000000000000));
#elif defined(TARGET_HPPA)
return const_float64(LIT64(0x7FF4000000000000));
#else
if (snan_bit_is_one(status)) {
return const_float64(LIT64(0x7FF7FFFFFFFFFFFF));
} else {
#if defined(TARGET_MIPS)
return const_float64(LIT64(0x7FF8000000000000));
#else
return const_float64(LIT64(0xFFF8000000000000));
#endif
}
#endif
}
/*----------------------------------------------------------------------------
| The pattern for a default generated extended double-precision NaN.
*----------------------------------------------------------------------------*/
floatx80 floatx80_default_nan(float_status *status)
{
floatx80 r;
/* None of the targets that have snan_bit_is_one use floatx80. */
assert(!snan_bit_is_one(status));
#if defined(TARGET_M68K)
r.low = LIT64(0xFFFFFFFFFFFFFFFF);
r.high = 0x7FFF;
#else
if (snan_bit_is_one(status)) {
r.low = LIT64(0xBFFFFFFFFFFFFFFF);
r.high = 0x7FFF;
} else {
r.low = LIT64(0xC000000000000000);
r.high = 0xFFFF;
}
/* X86 */
r.low = LIT64(0xC000000000000000);
r.high = 0xFFFF;
#endif
return r;
}
@ -285,27 +213,6 @@ floatx80 floatx80_default_nan(float_status *status)
const floatx80 floatx80_infinity
= make_floatx80_init(floatx80_infinity_high, floatx80_infinity_low);
/*----------------------------------------------------------------------------
| The pattern for a default generated quadruple-precision NaN.
*----------------------------------------------------------------------------*/
float128 float128_default_nan(float_status *status)
{
float128 r;
if (snan_bit_is_one(status)) {
r.low = LIT64(0xFFFFFFFFFFFFFFFF);
r.high = LIT64(0x7FFF7FFFFFFFFFFF);
} else {
r.low = LIT64(0x0000000000000000);
#if defined(TARGET_S390X) || defined(TARGET_PPC) || defined(TARGET_RISCV)
r.high = LIT64(0x7FFF800000000000);
#else
r.high = LIT64(0xFFFF800000000000);
#endif
}
return r;
}
/*----------------------------------------------------------------------------
| Raises the exceptions specified by `flags'. Floating-point traps can be
| defined here if desired. It is currently not possible for such a trap

41
qemu/fpu/softfloat.c
View file

@ -2093,6 +2093,47 @@ float64 QEMU_FLATTEN float64_sqrt(float64 a, float_status *status)
return float64_round_pack_canonical(pr, status);
}
/*----------------------------------------------------------------------------
| The pattern for a default generated NaN.
*----------------------------------------------------------------------------*/
float16 float16_default_nan(float_status *status)
{
FloatParts p = parts_default_nan(status);
p.frac >>= float16_params.frac_shift;
return float16_pack_raw(p);
}
float32 float32_default_nan(float_status *status)
{
FloatParts p = parts_default_nan(status);
p.frac >>= float32_params.frac_shift;
return float32_pack_raw(p);
}
float64 float64_default_nan(float_status *status)
{
FloatParts p = parts_default_nan(status);
p.frac >>= float64_params.frac_shift;
return float64_pack_raw(p);
}
float128 float128_default_nan(float_status *status)
{
FloatParts p = parts_default_nan(status);
float128 r;
/* Extrapolate from the choices made by parts_default_nan to fill
* in the quad-floating format. If the low bit is set, assume we
* want to set all non-snan bits.
*/
r.low = -(p.frac & 1);
r.high = p.frac >> (DECOMPOSED_BINARY_POINT - 48);
r.high |= LIT64(0x7FFF000000000000);
r.high |= (uint64_t)p.sign << 63;
return r;
}
/*----------------------------------------------------------------------------
| Takes a 64-bit fixed-point value `absZ' with binary point between bits 6