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softfloat: Reduce FloatFmt 

Remove frac_lsb, frac_lsbm1, roundeven_mask.  Compute
these from round_mask in parts$N_uncanon_normal.

With floatx80, round_mask will not be tied to frac_shift.
Everything else is easily computable.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2020-11-20 18:28:31 -08:00
parent 25fdedf0d3
commit d6e1f0cd59
2 changed files with 15 additions and 20 deletions
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6
fpu/softfloat-parts.c.inc
View File

@ -145,10 +145,10 @@ static void partsN(uncanon_normal)(FloatPartsN *p, float_status *s,
{
const int exp_max = fmt->exp_max;
const int frac_shift = fmt->frac_shift;
const uint64_t frac_lsb = fmt->frac_lsb;
const uint64_t frac_lsbm1 = fmt->frac_lsbm1;
const uint64_t round_mask = fmt->round_mask;
const uint64_t roundeven_mask = fmt->roundeven_mask;
const uint64_t frac_lsb = round_mask + 1;
const uint64_t frac_lsbm1 = round_mask ^ (round_mask >> 1);
const uint64_t roundeven_mask = round_mask | frac_lsb;
uint64_t inc;
bool overflow_norm = false;
int exp, flags = 0;

29
fpu/softfloat.c
View File

@ -563,9 +563,7 @@ typedef struct {
* frac_size: the size of the fraction field
* frac_shift: shift to normalise the fraction with DECOMPOSED_BINARY_POINT
* The following are computed based the size of fraction
* frac_lsb: least significant bit of fraction
* frac_lsbm1: the bit below the least significant bit (for rounding)
* round_mask/roundeven_mask: masks used for rounding
* round_mask: bits below lsb which must be rounded
* The following optional modifiers are available:
* arm_althp: handle ARM Alternative Half Precision
*/
@ -575,24 +573,21 @@ typedef struct {
int exp_max;
int frac_size;
int frac_shift;
uint64_t frac_lsb;
uint64_t frac_lsbm1;
uint64_t round_mask;
uint64_t roundeven_mask;
bool arm_althp;
uint64_t round_mask;
} FloatFmt;
/* Expand fields based on the size of exponent and fraction */
#define FLOAT_PARAMS(E, F) \
.exp_size = E, \
.exp_bias = ((1 << E) - 1) >> 1, \
.exp_max = (1 << E) - 1, \
.frac_size = F, \
.frac_shift = (-F - 1) & 63, \
.frac_lsb = 1ull << ((-F - 1) & 63), \
.frac_lsbm1 = 1ull << ((-F - 2) & 63), \
.round_mask = (1ull << ((-F - 1) & 63)) - 1, \
.roundeven_mask = (2ull << ((-F - 1) & 63)) - 1
#define FLOAT_PARAMS_(E, F) \
.exp_size = E, \
.exp_bias = ((1 << E) - 1) >> 1, \
.exp_max = (1 << E) - 1, \
.frac_size = F
#define FLOAT_PARAMS(E, F) \
FLOAT_PARAMS_(E, F), \
.frac_shift = (-F - 1) & 63, \
.round_mask = (1ull << ((-F - 1) & 63)) - 1
static const FloatFmt float16_params = {
FLOAT_PARAMS(5, 10)