mirror of
https://github.com/netwide-assembler/nasm.git
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Unify all standard IEEE floating-point formats; add 128-bit
Unify all the standard IEEE formats into one function, add support for IEEE standard 128-bit floating point numbers. The 80-bit format is still special since it explicitly represents the integer portion.
This commit is contained in:
H. Peter Anvin
parent
cfbe7c3cc2
commit
e31747e95b
206
float.c
206
float.c
@ -18,8 +18,8 @@
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#define TRUE 1
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#define FALSE 0
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#define MANT_WORDS 6 /* 64 bits + 32 for accuracy == 96 */
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#define MANT_DIGITS 28 /* 29 digits don't fit in 96 bits */
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#define MANT_WORDS 10 /* 112 bits + 48 for accuracy == 160 */
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#define MANT_DIGITS 49 /* 50 digits don't fit in 160 bits */
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/*
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* guaranteed top bit of from is set
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@ -47,9 +47,8 @@ static int ieee_multiply(uint16_t *to, uint16_t *from)
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temp[i] &= 0xFFFF;
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}
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if (temp[0] & 0x8000) {
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for (i = 0; i < MANT_WORDS; i++)
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to[i] = temp[i] & 0xFFFF;
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return 0;
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memcpy(to, temp, 2*MANT_WORDS);
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return 0;
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} else {
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for (i = 0; i < MANT_WORDS; i++)
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to[i] = (temp[i] << 1) + !!(temp[i + 1] & 0x8000);
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@ -213,75 +212,33 @@ 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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/* 64-bit format with 52-bit mantissa and 11-bit exponent */
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static int to_double(char *str, int32_t sign, uint8_t *result,
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efunc error)
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{
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uint16_t mant[MANT_WORDS];
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int32_t exponent;
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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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sign = (sign < 0 ? 0x8000L : 0L);
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- the sign bit is the MSB, followed by the exponent.
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- the sign bit plus exponent fit in 16 bits.
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- the exponent bias is 2^(n-1)-1 for an n-bit exponent */
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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 >= -1022 && exponent <= 1024) {
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/*
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* Normalised.
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*/
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exponent += 1023;
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ieee_shr(mant, 11);
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ieee_round(mant, 4);
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if (mant[0] & 0x20) /* did we scale up by one? */
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ieee_shr(mant, 1), exponent++;
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mant[0] &= 0xF; /* remove leading one */
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put(result + 6, (exponent << 4) | mant[0] | sign);
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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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} else if (exponent < -1022 && exponent >= -1074) {
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/*
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* Denormal.
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*/
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int shift = -(exponent + 1011);
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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, 4 - 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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put(result + 6, (wds == 0 ? mant[0] : 0) | sign);
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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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} 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, 8);
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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, 8);
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}
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return 1; /* success */
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}
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struct ieee_format {
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int words;
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int mantissa; /* Bits in the mantissa */
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int exponent; /* Bits in the exponent */
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};
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/* 32-bit format with 23-bit mantissa and 8-bit exponent */
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static const struct ieee_format ieee_16 = { 1, 10, 5 };
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static const struct ieee_format ieee_32 = { 2, 23, 8 };
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static const struct ieee_format ieee_64 = { 4, 52, 11 };
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static const struct ieee_format ieee_128 = { 8, 112, 15 };
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/* Produce all the standard IEEE formats: 16, 32, 64, and 128 bits */
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static int to_float(char *str, int32_t sign, uint8_t *result,
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efunc error)
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const struct ieee_format *fmt, efunc error)
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{
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uint16_t mant[MANT_WORDS];
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uint16_t mant[MANT_WORDS], *mp;
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int32_t exponent;
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int32_t expmax = 1 << (fmt->exponent-1);
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uint16_t implicit_one = 0x8000 >> fmt->exponent;
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int i;
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sign = (sign < 0 ? 0x8000L : 0L);
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@ -291,101 +248,64 @@ static int to_float(char *str, int32_t sign, uint8_t *result,
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* Non-zero.
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*/
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exponent--;
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if (exponent >= -126 && exponent <= 128) {
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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 += 127;
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ieee_shr(mant, 8);
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ieee_round(mant, 2);
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if (mant[0] & 0x100) /* did we scale up by one? */
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ieee_shr(mant, 1), exponent++;
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mant[0] &= 0x7F; /* remove leading one */
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put(result + 2, (exponent << 7) | mant[0] | sign);
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put(result + 0, mant[1]);
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} else if (exponent < -126 && exponent >= -149) {
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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 && 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 + 118);
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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, 2 - wds)
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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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put(result + 2, (wds == 0 ? mant[0] : 0) | sign);
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put(result + 0, (wds <= 1 ? mant[1 - wds] : 0));
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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(result, 0, 4);
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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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memset(result, 0, 4);
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/* Zero */
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memset(mant, 0, 2*fmt->words);
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}
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return 1;
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}
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/* 16-bit format with 10-bit mantissa and 5-bit exponent.
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Defined in IEEE 754r. Used in SSE5. See the AMD SSE5 manual, AMD
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document number 43479. */
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static int to_float16(char *str, int32_t sign, uint8_t *result,
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efunc error)
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{
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uint16_t mant[MANT_WORDS];
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int32_t exponent;
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mant[0] |= sign;
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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 >= -14 && exponent <= 16) {
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/*
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* Normalised.
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*/
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exponent += 15;
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ieee_shr(mant, 5);
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ieee_round(mant, 1);
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if (mant[0] & 0x800) /* did we scale up by one? */
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ieee_shr(mant, 1), exponent++;
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mant[0] &= 0x3FF; /* remove leading one */
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put(result + 0, (exponent << 7) | mant[0] | sign);
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} else if (exponent < -14 && exponent >= -24) {
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/*
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* Denormal.
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*/
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int shift = -(exponent + 8);
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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, 1 - 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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put(result + 0, (wds == 0 ? mant[0] : 0) | 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, 2);
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}
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} else {
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memset(result, 0, 2);
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for (mp = &mant[fmt->words], i = 0; i < fmt->words; i++) {
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uint16_t m = *--mp;
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put(result, m);
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result += 2;
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}
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return 1;
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return 1; /* success */
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}
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/* 80-bit format with 64-bit mantissa *including an explicit integer 1*
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@ -456,13 +376,15 @@ int float_const(char *number, int32_t sign, uint8_t *result, int bytes,
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{
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switch (bytes) {
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case 2:
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return to_float16(number, sign, result, error);
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return to_float(number, sign, result, &ieee_16, error);
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case 4:
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return to_float(number, sign, result, error);
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return to_float(number, sign, result, &ieee_32, error);
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case 8:
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return to_double(number, sign, result, error);
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return to_float(number, sign, result, &ieee_64, error);
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case 10:
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return to_ldoub(number, sign, result, error);
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case 16:
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return to_float(number, sign, result, &ieee_128, error);
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default:
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error(ERR_PANIC, "strange value %d passed to float_const", bytes);
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return 0;
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103
test/float.asm
Normal file
103
test/float.asm
Normal file
@ -0,0 +1,103 @@
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;
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; Test of floating-point formats
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;
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; 16-bit
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dw 1.0
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dw +1.0
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dw -1.0
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dw 0.0
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dw +0.0
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dw -0.0
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dw 1.83203125
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dw +1.83203125
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dw -1.83203125
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dw 1.83203125e3
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dw +1.83203125e3
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dw -1.83203125e3
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dw 1.83203125e-3
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dw +1.83203125e-3
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dw -1.83203125e-3
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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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; 32-bit
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dd 1.0
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dd +1.0
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dd -1.0
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dd 0.0
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dd +0.0
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dd -0.0
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dd 1.83203125
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dd +1.83203125
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dd -1.83203125
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dd 1.83203125e15
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dd +1.83203125e15
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dd -1.83203125e15
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dd 1.83203125e-15
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dd +1.83203125e-15
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dd -1.83203125e-15
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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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; 64-bit
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dq 1.0
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dq +1.0
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dq -1.0
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dq 0.0
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dq +0.0
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dq -0.0
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dq 1.83203125
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dq +1.83203125
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dq -1.83203125
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dq 1.83203125e300
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dq +1.83203125e300
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dq -1.83203125e300
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dq 1.83203125e-300
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dq +1.83203125e-300
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dq -1.83203125e-300
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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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; 80-bit
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dt 1.0
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dt +1.0
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dt -1.0
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dt 0.0
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dt +0.0
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dt -0.0
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dt 1.83203125
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dt +1.83203125
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dt -1.83203125
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dt 1.83203125e+4000
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dt +1.83203125e+4000
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dt -1.83203125e+4000
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dt 1.83203125e-4000
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dt +1.83203125e-4000
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dt -1.83203125e-4000
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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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; 128-bit
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do 1.0
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do +1.0
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do -1.0
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do 0.0
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do +0.0
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do -0.0
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do 1.83203125
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do +1.83203125
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do -1.83203125
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do 1.83203125e+4000
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do +1.83203125e+4000
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do -1.83203125e+4000
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do 1.83203125e-4000
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do +1.83203125e-4000
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do -1.83203125e-4000
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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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