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Support generating NaNs and infinities
Support generating NaNs and infinities as part of floating-point constants.
This commit is contained in:
H. Peter Anvin
parent
5107d672a0
commit
f48bc6fb48
184
float.c
184
float.c
@ -303,6 +303,12 @@ static int ieee_round(uint16_t *mant, int i)
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#define put(a,b) ( (*(a)=(b)), ((a)[1]=(b)>>8) )
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/* Set a bit, using *bigendian* bit numbering (0 = MSB) */
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static void set_bit(uint16_t *mant, int bit)
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{
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mant[bit >> 4] |= 1 << (~bit & 15);
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}
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/* Produce standard IEEE formats, with implicit "1" bit; this makes
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the following assumptions:
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@ -333,59 +339,84 @@ static int to_float(char *str, int32_t sign, uint8_t *result,
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sign = (sign < 0 ? 0x8000L : 0L);
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ieee_flconvert(str, mant, &exponent, error);
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if (mant[0] & 0x8000) {
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/*
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* Non-zero.
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*/
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exponent--;
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if (exponent >= 2-expmax && exponent <= expmax) {
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/*
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* Normalised.
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*/
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exponent += expmax;
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ieee_shr(mant, fmt->exponent);
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ieee_round(mant, fmt->words);
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/* did we scale up by one? */
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if (mant[0] & (implicit_one << 1)) {
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ieee_shr(mant, 1);
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exponent++;
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}
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if (str[0] == '_') {
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/* NaN or Infinity */
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int32_t expmask = (1 << fmt->exponent)-1;
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mant[0] &= (implicit_one-1); /* remove leading one */
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mant[0] |= exponent << (15 - fmt->exponent);
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} else if (exponent < 2-expmax && exponent >= 2-expmax-fmt->mantissa) {
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/*
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* Denormal.
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*/
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int shift = -(exponent + expmax-2-fmt->exponent);
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int sh = shift % 16, wds = shift / 16;
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ieee_shr(mant, sh);
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if (ieee_round(mant, fmt->words - wds)
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|| (sh > 0 && (mant[0] & (0x8000 >> (sh - 1))))) {
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ieee_shr(mant, 1);
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if (sh == 0)
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mant[0] |= 0x8000;
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exponent++;
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}
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memset(mant, 0, sizeof mant);
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mant[0] = expmask << (15-fmt->exponent); /* Exponent: all bits one */
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if (wds) {
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for (i = fmt->words-1; i >= wds; i--)
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mant[i] = mant[i-wds];
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for (; i >= 0; i--)
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mant[i] = 0;
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}
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} else {
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if (exponent > 0) {
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error(ERR_NONFATAL, "overflow in floating-point constant");
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return 0;
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} else {
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memset(mant, 0, 2*fmt->words);
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}
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}
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switch (str[2]) {
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case 'n': /* __nan__ */
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case 'N':
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case 'q': /* __qnan__ */
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case 'Q':
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set_bit(mant, fmt->exponent+1); /* Highest bit in mantissa */
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break;
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case 's': /* __snan__ */
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case 'S':
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set_bit(mant, fmt->exponent+fmt->mantissa); /* Last bit */
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break;
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case 'i': /* __infinity__ */
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case 'I':
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break;
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}
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} else {
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/* Zero */
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memset(mant, 0, 2*fmt->words);
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ieee_flconvert(str, mant, &exponent, error);
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if (mant[0] & 0x8000) {
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/*
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* Non-zero.
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*/
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exponent--;
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if (exponent >= 2-expmax && exponent <= expmax) {
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/*
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* Normalised.
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*/
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exponent += expmax;
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ieee_shr(mant, fmt->exponent);
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ieee_round(mant, fmt->words);
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/* did we scale up by one? */
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if (mant[0] & (implicit_one << 1)) {
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ieee_shr(mant, 1);
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exponent++;
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}
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mant[0] &= (implicit_one-1); /* remove leading one */
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mant[0] |= exponent << (15 - fmt->exponent);
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} else if (exponent < 2-expmax &&
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exponent >= 2-expmax-fmt->mantissa) {
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/*
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* Denormal.
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*/
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int shift = -(exponent + expmax-2-fmt->exponent);
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int sh = shift % 16, wds = shift / 16;
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ieee_shr(mant, sh);
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if (ieee_round(mant, fmt->words - wds)
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|| (sh > 0 && (mant[0] & (0x8000 >> (sh - 1))))) {
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ieee_shr(mant, 1);
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if (sh == 0)
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mant[0] |= 0x8000;
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exponent++;
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}
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if (wds) {
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for (i = fmt->words-1; i >= wds; i--)
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mant[i] = mant[i-wds];
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for (; i >= 0; i--)
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mant[i] = 0;
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}
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} else {
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if (exponent > 0) {
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error(ERR_NONFATAL, "overflow in floating-point constant");
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return 0;
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} else {
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memset(mant, 0, 2*fmt->words);
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}
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}
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} else {
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/* Zero */
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memset(mant, 0, 2*fmt->words);
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}
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}
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mant[0] |= sign;
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@ -409,6 +440,31 @@ static int to_ldoub(char *str, int32_t sign, uint8_t *result,
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sign = (sign < 0 ? 0x8000L : 0L);
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if (str[0] == '_') {
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uint16_t is_snan = 0, is_qnan = 0x8000;
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switch (str[2]) {
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case 'n':
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case 'N':
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case 'q':
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case 'Q':
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is_qnan = 0xc000;
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break;
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case 's':
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case 'S':
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is_snan = 1;
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break;
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case 'i':
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case 'I':
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break;
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}
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put(result + 0, is_snan);
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put(result + 2, 0);
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put(result + 4, 0);
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put(result + 6, is_qnan);
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put(result + 8, 0x7fff|sign);
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return 1;
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}
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ieee_flconvert(str, mant, &exponent, error);
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if (mant[0] & 0x8000) {
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/*
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@ -422,11 +478,11 @@ static int to_ldoub(char *str, int32_t sign, uint8_t *result,
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exponent += 16383;
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if (ieee_round(mant, 4)) /* did we scale up by one? */
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ieee_shr(mant, 1), mant[0] |= 0x8000, exponent++;
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put(result + 8, exponent | sign);
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put(result + 6, mant[0]);
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put(result + 4, mant[1]);
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put(result + 2, mant[2]);
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put(result + 0, mant[3]);
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put(result + 2, mant[2]);
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put(result + 4, mant[1]);
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put(result + 6, mant[0]);
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put(result + 8, exponent | sign);
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} else if (exponent < -16383 && exponent >= -16446) {
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/*
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* Denormal.
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@ -441,23 +497,29 @@ static int to_ldoub(char *str, int32_t sign, uint8_t *result,
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mant[0] |= 0x8000;
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exponent++;
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}
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put(result + 8, sign);
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put(result + 6, (wds == 0 ? mant[0] : 0));
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put(result + 4, (wds <= 1 ? mant[1 - wds] : 0));
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put(result + 2, (wds <= 2 ? mant[2 - wds] : 0));
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put(result + 0, (wds <= 3 ? mant[3 - wds] : 0));
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put(result + 2, (wds <= 2 ? mant[2 - wds] : 0));
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put(result + 4, (wds <= 1 ? mant[1 - wds] : 0));
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put(result + 6, (wds == 0 ? mant[0] : 0));
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put(result + 8, sign);
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} else {
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if (exponent > 0) {
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error(ERR_NONFATAL, "overflow in floating-point constant");
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return 0;
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} else
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memset(result, 0, 10);
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} else {
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goto zero;
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}
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}
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} else {
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/*
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* Zero.
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*/
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memset(result, 0, 10);
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zero:
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put(result + 0, 0);
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put(result + 2, 0);
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put(result + 4, 0);
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put(result + 6, 0);
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put(result + 8, sign);
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}
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return 1;
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}
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4
insns.h
4
insns.h
@ -12,10 +12,10 @@
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#include "nasm.h"
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/* max length of any instruction, register name etc. */
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#if MAX_INSLEN > 9 /* MAX_INSLEN defined in insnsi.h */
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#if MAX_INSLEN > 12 /* MAX_INSLEN defined in insnsi.h */
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#define MAX_KEYWORD MAX_INSLEN
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#else
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#define MAX_KEYWORD 9
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#define MAX_KEYWORD 12
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#endif
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struct itemplate {
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@ -21,6 +21,12 @@
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dw 1.83203125e-6 ; Denormal!
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dw +1.83203125e-6 ; Denormal!
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dw -1.83203125e-6 ; Denormal!
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dw __Infinity__
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dw +__Infinity__
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dw -__Infinity__
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dw __NaN__
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dw __QNaN__
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dw __SNaN__
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; 32-bit
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dd 1.0
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@ -41,6 +47,12 @@
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dd 1.83203125e-40 ; Denormal!
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dd +1.83203125e-40 ; Denormal!
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dd -1.83203125e-40 ; Denormal!
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dd __Infinity__
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dd +__Infinity__
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dd -__Infinity__
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dd __NaN__
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dd __QNaN__
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dd __SNaN__
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; 64-bit
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dq 1.0
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@ -61,6 +73,12 @@
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dq 1.83203125e-320 ; Denormal!
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dq +1.83203125e-320 ; Denormal!
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dq -1.83203125e-320 ; Denormal!
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dq __Infinity__
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dq +__Infinity__
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dq -__Infinity__
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dq __NaN__
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dq __QNaN__
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dq __SNaN__
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; 80-bit
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dt 1.0
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@ -81,6 +99,12 @@
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dt 1.83203125e-4940 ; Denormal!
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dt +1.83203125e-4940 ; Denormal!
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dt -1.83203125e-4940 ; Denormal!
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dt __Infinity__
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dt +__Infinity__
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dt -__Infinity__
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dt __NaN__
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dt __QNaN__
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dt __SNaN__
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; 128-bit
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do 1.0
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@ -101,3 +125,9 @@
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do 1.83203125e-4940 ; Denormal!
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do +1.83203125e-4940 ; Denormal!
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do -1.83203125e-4940 ; Denormal!
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do __Infinity__
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do +__Infinity__
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do -__Infinity__
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do __NaN__
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do __QNaN__
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do __SNaN__
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@ -32,6 +32,12 @@ to
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tword
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word
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% TOKEN_FLOAT, 0, 0
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__infinity__
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__nan__
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__qnan__
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__snan__
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% TOKEN_*, 0, 0
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seg
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wrt
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