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berkeley-softfloat-3
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Continuing f32_to_bf16 development

This commit is contained in:
Nicolas Brunie 2023-08-12 08:00:12 +02:00
parent ac8688db85
commit fab20258f0
3 changed files with 14 additions and 12 deletions
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2
source/RISCV/specialize.h
View File

@ -120,7 +120,7 @@ uint_fast16_t
/*----------------------------------------------------------------------------
| The bit pattern for a default generated 16-bit BF16 floating-point NaN.
*----------------------------------------------------------------------------*/
#define defaultNaNF16UI 0x7FC0
#define defaultNaNBF16UI 0x7FC0
/*----------------------------------------------------------------------------
| Converts the common NaN pointed to by 'aPtr' into a 16-bit floating-point

3
source/f32_to_bf16.c
View File

@ -75,7 +75,8 @@ bfloat16_t f32_to_bf16( float32_t a )
}
/*------------------------------------------------------------------------
*------------------------------------------------------------------------*/
frac16 = frac>>16 | ((frac & 0xFFFF) != 0);
// frac is a 24-bit mantissa, right shifted by
frac16 = frac>>9 | ((frac & 0x1FF) != 0);
if ( ! (exp | frac16) ) {
uiZ = packToBF16UI( sign, 0, 0 );
goto uiZ;

21
source/s_roundPackToBF16.c
View File

@ -40,6 +40,7 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include "internals.h"
#include "softfloat.h"
/** sig last significant bit is sig[7], the 7 LSBs will be used for rounding */
bfloat16_t
softfloat_roundPackToBF16( bool sign, int_fast16_t exp, uint_fast16_t sig )
{
@ -54,18 +55,18 @@ bfloat16_t
*------------------------------------------------------------------------*/
roundingMode = softfloat_roundingMode;
roundNearEven = (roundingMode == softfloat_round_near_even);
roundIncrement = 0x8;
roundIncrement = 0x40;
if ( ! roundNearEven && (roundingMode != softfloat_round_near_maxMag) ) {
roundIncrement =
(roundingMode
== (sign ? softfloat_round_min : softfloat_round_max))
? 0xF
? 0x7F
: 0;
}
roundBits = sig & 0xF;
roundBits = sig & 0x7F;
/*------------------------------------------------------------------------
*------------------------------------------------------------------------*/
if ( 0x1D <= (unsigned int) exp ) {
if ( 0xFD <= (unsigned int) exp ) {
if ( exp < 0 ) {
/*----------------------------------------------------------------
*----------------------------------------------------------------*/
@ -74,22 +75,22 @@ bfloat16_t
|| (exp < -1) || (sig + roundIncrement < 0x8000);
sig = softfloat_shiftRightJam32( sig, -exp );
exp = 0;
roundBits = sig & 0xF;
roundBits = sig & 0x7F;
if ( isTiny && roundBits ) {
softfloat_raiseFlags( softfloat_flag_underflow );
}
} else if ( (0x1D < exp) || (0x8000 <= sig + roundIncrement) ) {
} else if ( (0xFD < exp) || (0x8000 <= sig + roundIncrement) ) {
/*----------------------------------------------------------------
*----------------------------------------------------------------*/
softfloat_raiseFlags(
softfloat_flag_overflow | softfloat_flag_inexact );
uiZ = packToF16UI( sign, 0x1F, 0 ) - ! roundIncrement;
uiZ = packToBF16UI( sign, 0xFF, 0 ) - ! roundIncrement;
goto uiZ;
}
}
/*------------------------------------------------------------------------
*------------------------------------------------------------------------*/
sig = (sig + roundIncrement)>>4;
sig = (sig + roundIncrement)>>7;
if ( roundBits ) {
softfloat_exceptionFlags |= softfloat_flag_inexact;
#ifdef SOFTFLOAT_ROUND_ODD
@ -99,12 +100,12 @@ bfloat16_t
}
#endif
}
sig &= ~(uint_fast16_t) (! (roundBits ^ 8) & roundNearEven);
sig &= ~(uint_fast16_t) (! (roundBits ^ 0x40) & roundNearEven);
if ( ! sig ) exp = 0;
/*------------------------------------------------------------------------
*------------------------------------------------------------------------*/
packReturn:
uiZ = packToF16UI( sign, exp, sig );
uiZ = packToBF16UI( sign, exp, sig );
uiZ:
uZ.ui = uiZ;
return uZ.f;