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fpu/softfloat: Replace float_class_msnan with parts_silence_nan

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With a canonical representation of NaNs, we can silence an SNaN
immediately rather than delay until the final format is known.

Backports commit 0bcfbcbea548656ff930394f296589728c2a0c5d from qemu
This commit is contained in:
Richard Henderson 2018-05-19 22:28:25 -04:00 committed by Lioncash
parent baf1d57071
commit e26a389129
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GPG key ID: 4E3C3CC1031BA9C7
2 changed files with 33 additions and 30 deletions
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23
qemu/fpu/softfloat-specialize.h
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@ -138,6 +138,29 @@ static FloatParts parts_default_nan(float_status *status)
return result;
}
/*----------------------------------------------------------------------------
| Returns a quiet NaN from a signalling NaN for the deconstructed
| floating-point parts.
*----------------------------------------------------------------------------*/
static FloatParts parts_silence_nan(FloatParts a, float_status *status)
{
#ifdef NO_SIGNALING_NANS
g_assert_not_reached();
#elif defined(TARGET_HPPA)
a.frac &= ~(1ULL << (DECOMPOSED_BINARY_POINT - 1));
a.frac |= 1ULL << (DECOMPOSED_BINARY_POINT - 2);
#else
if (status->snan_bit_is_one) {
return parts_default_nan(status);
} else {
a.frac |= 1ULL << (DECOMPOSED_BINARY_POINT - 1);
}
#endif
a.cls = float_class_qnan;
return a;
}
/*----------------------------------------------------------------------------
| The pattern for a default generated half-precision NaN.
*----------------------------------------------------------------------------*/

40
qemu/fpu/softfloat.c
View file

@ -188,7 +188,6 @@ typedef enum __attribute__ ((__packed__)) {
float_class_inf,
float_class_qnan, /* all NaNs from here */
float_class_snan,
float_class_msnan, /* maybe silenced */
} FloatClass;
/*
@ -492,14 +491,7 @@ static FloatParts float16_unpack_canonical(float16 f, float_status *s)
static float16 float16_round_pack_canonical(FloatParts p, float_status *s)
{
switch (p.cls) {
case float_class_msnan:
p.frac >>= float16_params.frac_shift;
return float16_maybe_silence_nan(float16_pack_raw(p), s);
default:
p = round_canonical(p, s, &float16_params);
return float16_pack_raw(p);
}
return float16_pack_raw(round_canonical(p, s, &float16_params));
}
static FloatParts float32_unpack_canonical(float32 f, float_status *s)
@ -509,14 +501,7 @@ static FloatParts float32_unpack_canonical(float32 f, float_status *s)
static float32 float32_round_pack_canonical(FloatParts p, float_status *s)
{
switch (p.cls) {
case float_class_msnan:
p.frac >>= float32_params.frac_shift;
return float32_maybe_silence_nan(float32_pack_raw(p), s);
default:
p = round_canonical(p, s, &float32_params);
return float32_pack_raw(p);
}
return float32_pack_raw(round_canonical(p, s, &float32_params));
}
static FloatParts float64_unpack_canonical(float64 f, float_status *s)
@ -526,14 +511,7 @@ static FloatParts float64_unpack_canonical(float64 f, float_status *s)
static float64 float64_round_pack_canonical(FloatParts p, float_status *s)
{
switch (p.cls) {
case float_class_msnan:
p.frac >>= float64_params.frac_shift;
return float64_maybe_silence_nan(float64_pack_raw(p), s);
default:
p = round_canonical(p, s, &float64_params);
return float64_pack_raw(p);
}
return float64_pack_raw(round_canonical(p, s, &float64_params));
}
/* Simple helpers for checking if what NaN we have */
@ -555,7 +533,7 @@ static FloatParts return_nan(FloatParts a, float_status *s)
switch (a.cls) {
case float_class_snan:
s->float_exception_flags |= float_flag_invalid;
a.cls = float_class_msnan;
a = parts_silence_nan(a, s);
/* fall through */
case float_class_qnan:
if (s->default_nan_mode) {
@ -584,7 +562,9 @@ static FloatParts pick_nan(FloatParts a, FloatParts b, float_status *s)
(a.frac == b.frac && a.sign < b.sign))) {
a = b;
}
a.cls = float_class_msnan;
if (is_snan(a.cls)) {
return parts_silence_nan(a, s);
}
}
return a;
}
@ -624,8 +604,10 @@ static FloatParts pick_nan_muladd(FloatParts a, FloatParts b, FloatParts c,
default:
g_assert_not_reached();
}
a.cls = float_class_msnan;
if (is_snan(a.cls)) {
return parts_silence_nan(a, s);
}
return a;
}
@ -1334,7 +1316,6 @@ static int64_t round_to_int_and_pack(FloatParts in, int rmode,
switch (p.cls) {
case float_class_snan:
case float_class_qnan:
case float_class_msnan:
s->float_exception_flags = orig_flags | float_flag_invalid;
return max;
case float_class_inf:
@ -1425,7 +1406,6 @@ static uint64_t round_to_uint_and_pack(FloatParts in, int rmode, uint64_t max,
switch (p.cls) {
case float_class_snan:
case float_class_qnan:
case float_class_msnan:
s->float_exception_flags = orig_flags | float_flag_invalid;
return max;
case float_class_inf: