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softfloat: Add float16 type and float16 NaN handling functions

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Add a float16 type to softfloat, rather than using bits16 directly.
Also add the missing functions float16_is_quiet_nan(),
float16_is_signaling_nan() and float16_maybe_silence_nan(),
which are needed for the float16 conversion routines.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
This commit is contained in:
Peter Maydell 2011-02-10 11:28:56 +00:00 • committed by Aurelien Jarno
parent d1a1eb7472
commit bb4d4bb376
4 changed files with 118 additions and 12 deletions
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63
fpu/softfloat-specialize.h
View file

@ -56,6 +56,69 @@ typedef struct {
bits64 high, low;
} commonNaNT;
/*----------------------------------------------------------------------------
| The pattern for a default generated half-precision NaN.
*----------------------------------------------------------------------------*/
#if defined(TARGET_ARM)
#define float16_default_nan make_float16(0x7E00)
#elif SNAN_BIT_IS_ONE
#define float16_default_nan make_float16(0x7DFF)
#else
#define float16_default_nan make_float16(0xFE00)
#endif
/*----------------------------------------------------------------------------
| Returns 1 if the half-precision floating-point value `a' is a quiet
| NaN; otherwise returns 0.
*----------------------------------------------------------------------------*/
int float16_is_quiet_nan(float16 a_)
{
uint16_t a = float16_val(a_);
#if SNAN_BIT_IS_ONE
return (((a >> 9) & 0x3F) == 0x3E) && (a & 0x1FF);
#else
return ((a & ~0x8000) >= 0x7c80);
#endif
}
/*----------------------------------------------------------------------------
| Returns 1 if the half-precision floating-point value `a' is a signaling
| NaN; otherwise returns 0.
*----------------------------------------------------------------------------*/
int float16_is_signaling_nan(float16 a_)
{
uint16_t a = float16_val(a_);
#if SNAN_BIT_IS_ONE
return ((a & ~0x8000) >= 0x7c80);
#else
return (((a >> 9) & 0x3F) == 0x3E) && (a & 0x1FF);
#endif
}
/*----------------------------------------------------------------------------
| Returns a quiet NaN if the half-precision floating point value `a' is a
| signaling NaN; otherwise returns `a'.
*----------------------------------------------------------------------------*/
float16 float16_maybe_silence_nan(float16 a_)
{
if (float16_is_signaling_nan(a_)) {
#if SNAN_BIT_IS_ONE
# if defined(TARGET_MIPS) || defined(TARGET_SH4)
return float16_default_nan;
# else
# error Rules for silencing a signaling NaN are target-specific
# endif
#else
uint16_t a = float16_val(a_);
a |= (1 << 9);
return make_float16(a);
#endif
}
return a_;
}
/*----------------------------------------------------------------------------
| The pattern for a default generated single-precision NaN.
*----------------------------------------------------------------------------*/