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fpu/softfloat: Specialize on snan_bit_is_one

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Only MIPS requires snan_bit_is_one to be variable. While we are
specializing softfloat behaviour, allow other targets to eliminate
this runtime check.

Backports commit 03385dfdaaa2dc31bbd07d13244a6b037bfab4cc from qemu
This commit is contained in:
Richard Henderson 2018-05-19 23:38:56 -04:00 committed by Lioncash
parent 9810a6d9d6
commit 79a4c4ed0f
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GPG key ID: 4E3C3CC1031BA9C7
2 changed files with 44 additions and 25 deletions
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68
qemu/fpu/softfloat-specialize.h
View file

@ -79,13 +79,31 @@ this code that are retained.
* version 2 or later. See the COPYING file in the top-level directory.
*/
#if defined(TARGET_XTENSA)
/* Define for architectures which deviate from IEEE in not supporting
* signaling NaNs (so all NaNs are treated as quiet).
*/
#if defined(TARGET_XTENSA)
#define NO_SIGNALING_NANS 1
#endif
/* Define how the architecture discriminates signaling NaNs.
* This done with the most significant bit of the fraction.
* In IEEE 754-1985 this was implementation defined, but in IEEE 754-2008
* the msb must be zero. MIPS is (so far) unique in supporting both the
* 2008 revision and backward compatibility with their original choice.
* Thus for MIPS we must make the choice at runtime.
*/
static inline flag snan_bit_is_one(float_status *status)
{
#if defined(TARGET_MIPS)
return status->snan_bit_is_one;
#elif defined(TARGET_HPPA) || defined(TARGET_UNICORE32) || defined(TARGET_SH4)
return 1;
#else
return 0;
#endif
}
/*----------------------------------------------------------------------------
| For the deconstructed floating-point with fraction FRAC, return true
| if the fraction represents a signalling NaN; otherwise false.
@ -97,7 +115,7 @@ static bool parts_is_snan_frac(uint64_t frac, float_status *status)
return false;
#else
flag msb = extract64(frac, DECOMPOSED_BINARY_POINT - 1, 1);
return msb == status->snan_bit_is_one;
return msb == snan_bit_is_one(status);
#endif
}
@ -119,7 +137,7 @@ static FloatParts parts_default_nan(float_status *status)
#elif defined(TARGET_HPPA)
frac = 1ULL << (DECOMPOSED_BINARY_POINT - 2);
#else
if (status->snan_bit_is_one) {
if (snan_bit_is_one(status)) {
frac = (1ULL << (DECOMPOSED_BINARY_POINT - 1)) - 1;
} else {
#if defined(TARGET_MIPS)
@ -151,7 +169,7 @@ static FloatParts parts_silence_nan(FloatParts a, float_status *status)
a.frac &= ~(1ULL << (DECOMPOSED_BINARY_POINT - 1));
a.frac |= 1ULL << (DECOMPOSED_BINARY_POINT - 2);
#else
if (status->snan_bit_is_one) {
if (snan_bit_is_one(status)) {
return parts_default_nan(status);
} else {
a.frac |= 1ULL << (DECOMPOSED_BINARY_POINT - 1);
@ -169,7 +187,7 @@ float16 float16_default_nan(float_status *status)
#if defined(TARGET_ARM)
return const_float16(0x7E00);
#else
if (status->snan_bit_is_one) {
if (snan_bit_is_one(status)) {
return const_float16(0x7DFF);
} else {
#if defined(TARGET_MIPS)
@ -195,7 +213,7 @@ float32 float32_default_nan(float_status *status)
#elif defined(TARGET_HPPA)
return const_float32(0x7FA00000);
#else
if (status->snan_bit_is_one) {
if (snan_bit_is_one(status)) {
return const_float32(0x7FBFFFFF);
} else {
#if defined(TARGET_MIPS)
@ -220,7 +238,7 @@ float64 float64_default_nan(float_status *status)
#elif defined(TARGET_HPPA)
return const_float64(LIT64(0x7FF4000000000000));
#else
if (status->snan_bit_is_one) {
if (snan_bit_is_one(status)) {
return const_float64(LIT64(0x7FF7FFFFFFFFFFFF));
} else {
#if defined(TARGET_MIPS)
@ -242,7 +260,7 @@ floatx80 floatx80_default_nan(float_status *status)
r.low = LIT64(0xFFFFFFFFFFFFFFFF);
r.high = 0x7FFF;
#else
if (status->snan_bit_is_one) {
if (snan_bit_is_one(status)) {
r.low = LIT64(0xBFFFFFFFFFFFFFFF);
r.high = 0x7FFF;
} else {
@ -274,7 +292,7 @@ float128 float128_default_nan(float_status *status)
{
float128 r;
if (status->snan_bit_is_one) {
if (snan_bit_is_one(status)) {
r.low = LIT64(0xFFFFFFFFFFFFFFFF);
r.high = LIT64(0x7FFF7FFFFFFFFFFF);
} else {
@ -319,7 +337,7 @@ int float16_is_quiet_nan(float16 a_, float_status *status)
return float16_is_any_nan(a_);
#else
uint16_t a = float16_val(a_);
if (status->snan_bit_is_one) {
if (snan_bit_is_one(status)) {
return (((a >> 9) & 0x3F) == 0x3E) && (a & 0x1FF);
} else {
return ((a & ~0x8000) >= 0x7C80);
@ -338,7 +356,7 @@ int float16_is_signaling_nan(float16 a_, float_status *status)
return 0;
#else
uint16_t a = float16_val(a_);
if (status->snan_bit_is_one) {
if (snan_bit_is_one(status)) {
return ((a & ~0x8000) >= 0x7C80);
} else {
return (((a >> 9) & 0x3F) == 0x3E) && (a & 0x1FF);
@ -356,7 +374,7 @@ float16 float16_silence_nan(float16 a, float_status *status)
#ifdef NO_SIGNALING_NANS
g_assert_not_reached();
#else
if (status->snan_bit_is_one) {
if (snan_bit_is_one(status)) {
return float16_default_nan(status);
} else {
return a | (1 << 9);
@ -375,7 +393,7 @@ int float32_is_quiet_nan(float32 a_, float_status *status)
return float32_is_any_nan(a_);
#else
uint32_t a = float32_val(a_);
if (status->snan_bit_is_one) {
if (snan_bit_is_one(status)) {
return (((a >> 22) & 0x1FF) == 0x1FE) && (a & 0x003FFFFF);
} else {
return ((uint32_t)(a << 1) >= 0xFF800000);
@ -394,7 +412,7 @@ int float32_is_signaling_nan(float32 a_, float_status *status)
return 0;
#else
uint32_t a = float32_val(a_);
if (status->snan_bit_is_one) {
if (snan_bit_is_one(status)) {
return ((uint32_t)(a << 1) >= 0xFF800000);
} else {
return (((a >> 22) & 0x1FF) == 0x1FE) && (a & 0x003FFFFF);
@ -412,7 +430,7 @@ float32 float32_silence_nan(float32 a, float_status *status)
#ifdef NO_SIGNALING_NANS
g_assert_not_reached();
#else
if (status->snan_bit_is_one) {
if (snan_bit_is_one(status)) {
# ifdef TARGET_HPPA
a &= ~0x00400000;
a |= 0x00200000;
@ -651,7 +669,7 @@ static int pickNaNMulAdd(flag aIsQNaN, flag aIsSNaN, flag bIsQNaN, flag bIsSNaN,
return 3;
}
if (status->snan_bit_is_one) {
if (snan_bit_is_one(status)) {
/* Prefer sNaN over qNaN, in the a, b, c order. */
if (aIsSNaN) {
return 0;
@ -786,7 +804,7 @@ int float64_is_quiet_nan(float64 a_, float_status *status)
return float64_is_any_nan(a_);
#else
uint64_t a = float64_val(a_);
if (status->snan_bit_is_one) {
if (snan_bit_is_one(status)) {
return (((a >> 51) & 0xFFF) == 0xFFE)
&& (a & 0x0007FFFFFFFFFFFFULL);
} else {
@ -806,7 +824,7 @@ int float64_is_signaling_nan(float64 a_, float_status *status)
return 0;
#else
uint64_t a = float64_val(a_);
if (status->snan_bit_is_one) {
if (snan_bit_is_one(status)) {
return ((a << 1) >= 0xFFF0000000000000ULL);
} else {
return (((a >> 51) & 0xFFF) == 0xFFE)
@ -825,7 +843,7 @@ float64 float64_silence_nan(float64 a, float_status *status)
#ifdef NO_SIGNALING_NANS
g_assert_not_reached();
#else
if (status->snan_bit_is_one) {
if (snan_bit_is_one(status)) {
# ifdef TARGET_HPPA
a &= ~0x0008000000000000ULL;
a |= 0x0004000000000000ULL;
@ -941,7 +959,7 @@ int floatx80_is_quiet_nan(floatx80 a, float_status *status)
#ifdef NO_SIGNALING_NANS
return floatx80_is_any_nan(a);
#else
if (status->snan_bit_is_one) {
if (snan_bit_is_one(status)) {
uint64_t aLow;
aLow = a.low & ~0x4000000000000000ULL;
@ -966,7 +984,7 @@ int floatx80_is_signaling_nan(floatx80 a, float_status *status)
#ifdef NO_SIGNALING_NANS
return 0;
#else
if (status->snan_bit_is_one) {
if (snan_bit_is_one(status)) {
return ((a.high & 0x7FFF) == 0x7FFF)
&& ((a.low << 1) >= 0x8000000000000000ULL);
} else {
@ -990,7 +1008,7 @@ floatx80 floatx80_silence_nan(floatx80 a, float_status *status)
#ifdef NO_SIGNALING_NANS
g_assert_not_reached();
#else
if (status->snan_bit_is_one) {
if (snan_bit_is_one(status)) {
return floatx80_default_nan(status);
} else {
a.low |= LIT64(0xC000000000000000);
@ -1104,7 +1122,7 @@ int float128_is_quiet_nan(float128 a, float_status *status)
#ifdef NO_SIGNALING_NANS
return float128_is_any_nan(a);
#else
if (status->snan_bit_is_one) {
if (snan_bit_is_one(status)) {
return (((a.high >> 47) & 0xFFFF) == 0xFFFE)
&& (a.low || (a.high & 0x00007FFFFFFFFFFFULL));
} else {
@ -1124,7 +1142,7 @@ int float128_is_signaling_nan(float128 a, float_status *status)
#ifdef NO_SIGNALING_NANS
return 0;
#else
if (status->snan_bit_is_one) {
if (snan_bit_is_one(status)) {
return ((a.high << 1) >= 0xFFFF000000000000ULL)
&& (a.low || (a.high & 0x0000FFFFFFFFFFFFULL));
} else {
@ -1144,7 +1162,7 @@ float128 float128_silence_nan(float128 a, float_status *status)
#ifdef NO_SIGNALING_NANS
g_assert_not_reached();
#else
if (status->snan_bit_is_one) {
if (snan_bit_is_one(status)) {
return float128_default_nan(status);
} else {
a.high |= LIT64(0x0000800000000000);

1
qemu/include/fpu/softfloat-types.h
View file

@ -173,6 +173,7 @@ typedef struct float_status {
/* should denormalised inputs go to zero and set the input_denormal flag? */
flag flush_inputs_to_zero;
flag default_nan_mode;
/* not always used -- see snan_bit_is_one() in softfloat-specialize.h */
flag snan_bit_is_one;
} float_status;