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Support 16-bit IEEE floating point; used in SSE5

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SSE5 supports standard IEEE 16-bit floating point, so we should
support that too.
This commit is contained in:
H. Peter Anvin 2007-09-18 16:39:03 -07:00
parent 510a2508e6
commit 141d7cf68d
2 changed files with 82 additions and 13 deletions
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71
float.c
View file

@ -213,6 +213,7 @@ static int ieee_round(uint16_t *mant, int i)
#define put(a,b) ( (*(a)=(b)), ((a)[1]=(b)>>8) )
/* 64-bit format with 52-bit mantissa and 11-bit exponent */
static int to_double(char *str, int32_t sign, uint8_t *result,
efunc error)
{
@ -275,6 +276,7 @@ static int to_double(char *str, int32_t sign, uint8_t *result,
return 1; /* success */
}
/* 32-bit format with 23-bit mantissa and 8-bit exponent */
static int to_float(char *str, int32_t sign, uint8_t *result,
efunc error)
{
@ -330,6 +332,64 @@ static int to_float(char *str, int32_t sign, uint8_t *result,
return 1;
}
/* 16-bit format with 10-bit mantissa and 5-bit exponent.
Defined in IEEE 754r. Used in SSE5. See the AMD SSE5 manual, AMD
document number 43479. */
static int to_float16(char *str, int32_t sign, uint8_t *result,
efunc error)
{
uint16_t mant[MANT_WORDS];
int32_t exponent;
sign = (sign < 0 ? 0x8000L : 0L);
ieee_flconvert(str, mant, &exponent, error);
if (mant[0] & 0x8000) {
/*
* Non-zero.
*/
exponent--;
if (exponent >= -14 && exponent <= 16) {
/*
* Normalised.
*/
exponent += 15;
ieee_shr(mant, 5);
ieee_round(mant, 1);
if (mant[0] & 0x800) /* did we scale up by one? */
ieee_shr(mant, 1), exponent++;
mant[0] &= 0x3FF; /* remove leading one */
put(result + 0, (exponent << 7) | mant[0] | sign);
} else if (exponent < -14 && exponent >= -24) {
/*
* Denormal.
*/
int shift = -(exponent + 8);
int sh = shift % 16, wds = shift / 16;
ieee_shr(mant, sh);
if (ieee_round(mant, 1 - wds)
|| (sh > 0 && (mant[0] & (0x8000 >> (sh - 1))))) {
ieee_shr(mant, 1);
if (sh == 0)
mant[0] |= 0x8000;
exponent++;
}
put(result + 0, (wds == 0 ? mant[0] : 0) | sign);
} else {
if (exponent > 0) {
error(ERR_NONFATAL, "overflow in floating-point constant");
return 0;
} else
memset(result, 0, 2);
}
} else {
memset(result, 0, 2);
}
return 1;
}
/* 80-bit format with 64-bit mantissa *including an explicit integer 1*
and 15-bit exponent. */
static int to_ldoub(char *str, int32_t sign, uint8_t *result,
efunc error)
{
@ -394,13 +454,16 @@ static int to_ldoub(char *str, int32_t sign, uint8_t *result,
int float_const(char *number, int32_t sign, uint8_t *result, int bytes,
efunc error)
{
if (bytes == 4)
switch (bytes) {
case 2:
return to_float16(number, sign, result, error);
case 4:
return to_float(number, sign, result, error);
else if (bytes == 8)
case 8:
return to_double(number, sign, result, error);
else if (bytes == 10)
case 10:
return to_ldoub(number, sign, result, error);
else {
default:
error(ERR_PANIC, "strange value %d passed to float_const", bytes);
return 0;
}

24
parser.c
View file

@ -230,30 +230,36 @@ insn *parse_line(int pass, char *buffer, insn * result,
if (i == TOKEN_FLOAT) {
eop->type = EOT_DB_STRING;
result->eops_float = TRUE;
if (result->opcode == I_DD)
switch (result->opcode) {
case I_DW:
eop->stringlen = 2;
break;
case I_DD:
eop->stringlen = 4;
else if (result->opcode == I_DQ)
break;
case I_DQ:
eop->stringlen = 8;
else if (result->opcode == I_DT)
break;
case I_DT:
eop->stringlen = 10;
else if (result->opcode == I_DO)
eop->stringlen = 16;
else {
break;
default:
error(ERR_NONFATAL, "floating-point constant"
" encountered in `D%c' instruction",
result->opcode == I_DW ? 'W' : 'B');
" encountered in `d%c' instruction"
? (result->opcode == I_DO) ? 'o' : 'b');
/*
* fix suggested by Pedro Gimeno... original line
* was:
* eop->type = EOT_NOTHING;
*/
eop->stringlen = 0;
break;
}
eop = nasm_realloc(eop, sizeof(extop) + eop->stringlen);
tail = &eop->next;
*fixptr = eop;
eop->stringval = (char *)eop + sizeof(extop);
if (eop->stringlen < 4 ||
if (!eop->stringlen ||
!float_const(tokval.t_charptr, sign,
(uint8_t *)eop->stringval,
eop->stringlen, error))