patch-2.2.18 linux/arch/m68k/math-emu/fp_arith.c

• Lines: 701
• Date: Fri Oct 13 23:36:54 2000
• Orig file: v2.2.17/arch/m68k/math-emu/fp_arith.c
• Orig date: Thu Jan 1 01:00:00 1970

diff -u --new-file --recursive --exclude-from /usr/src/exclude v2.2.17/arch/m68k/math-emu/fp_arith.c linux/arch/m68k/math-emu/fp_arith.c
@@ -0,0 +1,700 @@
+/*
+
+   fp_arith.c: floating-point math routines for the Linux-m68k
+   floating point emulator.
+
+   Copyright (c) 1998-1999 David Huggins-Daines.
+
+   Somewhat based on the AlphaLinux floating point emulator, by David
+   Mosberger-Tang.
+
+   You may copy, modify, and redistribute this file under the terms of
+   the GNU General Public License, version 2, or any later version, at
+   your convenience.
+ */
+
+#include "fp_emu.h"
+#include "multi_arith.h"
+#include "fp_arith.h"
+
+const struct fp_ext fp_QNaN =
+{
+	0, 0, 0x7fff, { ~0 }
+};
+
+const struct fp_ext fp_Inf =
+{
+	0, 0, 0x7fff, { 0 }
+};
+
+/* let's start with the easy ones */
+
+struct fp_ext *
+fp_fabs(struct fp_ext *dest, struct fp_ext *src)
+{
+	dprint(PINSTR, "fabs\n");
+
+	fp_monadic_check(dest, src);
+
+	dest->sign = 0;
+
+	return dest;
+}
+
+struct fp_ext *
+fp_fneg(struct fp_ext *dest, struct fp_ext *src)
+{
+	dprint(PINSTR, "fneg\n");
+
+	fp_monadic_check(dest, src);
+
+	dest->sign = !dest->sign;
+
+	return dest;
+}
+
+/* Now, the slightly harder ones */
+
+/* fp_fadd: Implements the kernel of the FADD, FSADD, FDADD, FSUB,
+   FDSUB, and FCMP instructions. */
+
+struct fp_ext *
+fp_fadd(struct fp_ext *dest, struct fp_ext *src)
+{
+	int diff;
+
+	dprint(PINSTR, "fadd\n");
+
+	fp_dyadic_check(dest, src);
+
+	if (IS_INF(dest)) {
+		/* infinity - infinity == NaN */
+		if (IS_INF(src) && (src->sign != dest->sign))
+			fp_set_nan(dest);
+		return dest;
+	}
+	if (IS_INF(src)) {
+		fp_copy_ext(dest, src);
+		return dest;
+	}
+
+	if (IS_ZERO(dest)) {
+		if (IS_ZERO(src)) {
+			if (src->sign != dest->sign) {
+				if (FPDATA->rnd == FPCR_ROUND_RM)
+					dest->sign = 1;
+				else
+					dest->sign = 0;
+			}
+		} else
+			fp_copy_ext(dest, src);
+		return dest;
+	}
+
+	dest->lowmant = src->lowmant = 0;
+
+	if ((diff = dest->exp - src->exp) > 0)
+		fp_denormalize(src, diff);
+	else if ((diff = -diff) > 0)
+		fp_denormalize(dest, diff);
+
+	if (dest->sign == src->sign) {
+		if (fp_addmant(dest, src))
+			if (!fp_addcarry(dest))
+				return dest;
+	} else {
+		if (dest->mant.m64 < src->mant.m64) {
+			fp_submant(dest, src, dest);
+			dest->sign = !dest->sign;
+		} else
+			fp_submant(dest, dest, src);
+	}
+
+	return dest;
+}
+
+/* fp_fsub: Implementes the kernel of the FSUB, FSSUB, and FDSUB
+   instructions.
+
+   Remember that the arguments are in assembler-syntax order! */
+
+struct fp_ext *
+fp_fsub(struct fp_ext *dest, struct fp_ext *src)
+{
+	dprint(PINSTR, "fsub ");
+
+	src->sign = !src->sign;
+	return fp_fadd(dest, src);
+}
+
+
+struct fp_ext *
+fp_fcmp(struct fp_ext *dest, struct fp_ext *src)
+{
+	dprint(PINSTR, "fcmp ");
+
+	FPDATA->temp[1] = *dest;
+	src->sign = !src->sign;
+	return fp_fadd(&FPDATA->temp[1], src);
+}
+
+struct fp_ext *
+fp_ftst(struct fp_ext *dest, struct fp_ext *src)
+{
+	dprint(PINSTR, "ftst\n");
+
+	(void)dest;
+
+	return src;
+}
+
+struct fp_ext *
+fp_fmul(struct fp_ext *dest, struct fp_ext *src)
+{
+	union fp_mant128 temp;
+	int exp;
+
+	dprint(PINSTR, "fmul\n");
+
+	fp_dyadic_check(dest, src);
+
+	/* calculate the correct sign now, as it's necessary for infinities */
+	dest->sign = src->sign ^ dest->sign;
+
+	/* Handle infinities */
+	if (IS_INF(dest)) {
+		if (IS_ZERO(src))
+			fp_set_nan(dest);
+		return dest;
+	}
+	if (IS_INF(src)) {
+		if (IS_ZERO(dest))
+			fp_set_nan(dest);
+		else
+			fp_copy_ext(dest, src);
+		return dest;
+	}
+
+	/* Of course, as we all know, zero * anything = zero.  You may
+	   not have known that it might be a positive or negative
+	   zero... */
+	if (IS_ZERO(dest) || IS_ZERO(src)) {
+		dest->exp = 0;
+		dest->mant.m64 = 0;
+		dest->lowmant = 0;
+
+		return dest;
+	}
+
+	exp = dest->exp + src->exp - 0x3ffe;
+
+	/* shift up the mantissa for denormalized numbers,
+	   so that the highest bit is set, this makes the
+	   shift of the result below easier */
+	if ((long)dest->mant.m32[0] >= 0)
+		exp -= fp_overnormalize(dest);
+	if ((long)src->mant.m32[0] >= 0)
+		exp -= fp_overnormalize(src);
+
+	/* now, do a 64-bit multiply with expansion */
+	fp_multiplymant(&temp, dest, src);
+
+	/* normalize it back to 64 bits and stuff it back into the
+	   destination struct */
+	if ((long)temp.m32[0] > 0) {
+		exp--;
+		fp_putmant128(dest, &temp, 1);
+	} else
+		fp_putmant128(dest, &temp, 0);
+
+	if (exp >= 0x7fff) {
+		fp_set_ovrflw(dest);
+		return dest;
+	}
+	dest->exp = exp;
+	if (exp < 0) {
+		fp_set_sr(FPSR_EXC_UNFL);
+		fp_denormalize(dest, -exp);
+	}
+
+	return dest;
+}
+
+/* fp_fdiv: Implements the "kernel" of the FDIV, FSDIV, FDDIV and
+   FSGLDIV instructions.
+
+   Note that the order of the operands is counter-intuitive: instead
+   of src / dest, the result is actually dest / src. */
+
+struct fp_ext *
+fp_fdiv(struct fp_ext *dest, struct fp_ext *src)
+{
+	union fp_mant128 temp;
+	int exp;
+
+	dprint(PINSTR, "fdiv\n");
+
+	fp_dyadic_check(dest, src);
+
+	/* calculate the correct sign now, as it's necessary for infinities */
+	dest->sign = src->sign ^ dest->sign;
+
+	/* Handle infinities */
+	if (IS_INF(dest)) {
+		/* infinity / infinity = NaN (quiet, as always) */
+		if (IS_INF(src))
+			fp_set_nan(dest);
+		/* infinity / anything else = infinity (with approprate sign) */
+		return dest;
+	}
+	if (IS_INF(src)) {
+		/* anything / infinity = zero (with appropriate sign) */
+		dest->exp = 0;
+		dest->mant.m64 = 0;
+		dest->lowmant = 0;
+
+		return dest;
+	}
+
+	/* zeroes */
+	if (IS_ZERO(dest)) {
+		/* zero / zero = NaN */
+		if (IS_ZERO(src))
+			fp_set_nan(dest);
+		/* zero / anything else = zero */
+		return dest;
+	}
+	if (IS_ZERO(src)) {
+		/* anything / zero = infinity (with appropriate sign) */
+		fp_set_sr(FPSR_EXC_DZ);
+		dest->exp = 0x7fff;
+		dest->mant.m64 = 0;
+
+		return dest;
+	}
+
+	exp = dest->exp - src->exp + 0x3fff;
+
+	/* shift up the mantissa for denormalized numbers,
+	   so that the highest bit is set, this makes lots
+	   of things below easier */
+	if ((long)dest->mant.m32[0] >= 0)
+		exp -= fp_overnormalize(dest);
+	if ((long)src->mant.m32[0] >= 0)
+		exp -= fp_overnormalize(src);
+
+	/* now, do the 64-bit divide */
+	fp_dividemant(&temp, dest, src);
+
+	/* normalize it back to 64 bits and stuff it back into the
+	   destination struct */
+	if (!temp.m32[0]) {
+		exp--;
+		fp_putmant128(dest, &temp, 32);
+	} else
+		fp_putmant128(dest, &temp, 31);
+
+	if (exp >= 0x7fff) {
+		fp_set_ovrflw(dest);
+		return dest;
+	}
+	dest->exp = exp;
+	if (exp < 0) {
+		fp_set_sr(FPSR_EXC_UNFL);
+		fp_denormalize(dest, -exp);
+	}
+
+	return dest;
+}
+
+struct fp_ext *
+fp_fsglmul(struct fp_ext *dest, struct fp_ext *src)
+{
+	int exp;
+
+	dprint(PINSTR, "fsglmul\n");
+
+	fp_dyadic_check(dest, src);
+
+	/* calculate the correct sign now, as it's necessary for infinities */
+	dest->sign = src->sign ^ dest->sign;
+
+	/* Handle infinities */
+	if (IS_INF(dest)) {
+		if (IS_ZERO(src))
+			fp_set_nan(dest);
+		return dest;
+	}
+	if (IS_INF(src)) {
+		if (IS_ZERO(dest))
+			fp_set_nan(dest);
+		else
+			fp_copy_ext(dest, src);
+		return dest;
+	}
+
+	/* Of course, as we all know, zero * anything = zero.  You may
+	   not have known that it might be a positive or negative
+	   zero... */
+	if (IS_ZERO(dest) || IS_ZERO(src)) {
+		dest->exp = 0;
+		dest->mant.m64 = 0;
+		dest->lowmant = 0;
+
+		return dest;
+	}
+
+	exp = dest->exp + src->exp - 0x3ffe;
+
+	/* do a 32-bit multiply */
+	fp_mul64(dest->mant.m32[0], dest->mant.m32[1],
+		 dest->mant.m32[0] & 0xffffff00,
+		 src->mant.m32[0] & 0xffffff00);
+
+	if (exp >= 0x7fff) {
+		fp_set_ovrflw(dest);
+		return dest;
+	}
+	dest->exp = exp;
+	if (exp < 0) {
+		fp_set_sr(FPSR_EXC_UNFL);
+		fp_denormalize(dest, -exp);
+	}
+
+	return dest;
+}
+
+struct fp_ext *
+fp_fsgldiv(struct fp_ext *dest, struct fp_ext *src)
+{
+	int exp;
+	unsigned long quot, rem;
+
+	dprint(PINSTR, "fsgldiv\n");
+
+	fp_dyadic_check(dest, src);
+
+	/* calculate the correct sign now, as it's necessary for infinities */
+	dest->sign = src->sign ^ dest->sign;
+
+	/* Handle infinities */
+	if (IS_INF(dest)) {
+		/* infinity / infinity = NaN (quiet, as always) */
+		if (IS_INF(src))
+			fp_set_nan(dest);
+		/* infinity / anything else = infinity (with approprate sign) */
+		return dest;
+	}
+	if (IS_INF(src)) {
+		/* anything / infinity = zero (with appropriate sign) */
+		dest->exp = 0;
+		dest->mant.m64 = 0;
+		dest->lowmant = 0;
+
+		return dest;
+	}
+
+	/* zeroes */
+	if (IS_ZERO(dest)) {
+		/* zero / zero = NaN */
+		if (IS_ZERO(src))
+			fp_set_nan(dest);
+		/* zero / anything else = zero */
+		return dest;
+	}
+	if (IS_ZERO(src)) {
+		/* anything / zero = infinity (with appropriate sign) */
+		fp_set_sr(FPSR_EXC_DZ);
+		dest->exp = 0x7fff;
+		dest->mant.m64 = 0;
+
+		return dest;
+	}
+
+	exp = dest->exp - src->exp + 0x3fff;
+
+	dest->mant.m32[0] &= 0xffffff00;
+	src->mant.m32[0] &= 0xffffff00;
+
+	/* do the 32-bit divide */
+	if (dest->mant.m32[0] >= src->mant.m32[0]) {
+		fp_sub64(dest->mant, src->mant);
+		fp_div64(quot, rem, dest->mant.m32[0], 0, src->mant.m32[0]);
+		dest->mant.m32[0] = 0x80000000 | (quot >> 1);
+		dest->mant.m32[1] = (quot & 1) | rem;	/* only for rounding */
+	} else {
+		fp_div64(quot, rem, dest->mant.m32[0], 0, src->mant.m32[0]);
+		dest->mant.m32[0] = quot;
+		dest->mant.m32[1] = rem;		/* only for rounding */
+		exp--;
+	}
+
+	if (exp >= 0x7fff) {
+		fp_set_ovrflw(dest);
+		return dest;
+	}
+	dest->exp = exp;
+	if (exp < 0) {
+		fp_set_sr(FPSR_EXC_UNFL);
+		fp_denormalize(dest, -exp);
+	}
+
+	return dest;
+}
+
+/* fp_roundint: Internal rounding function for use by several of these
+   emulated instructions.
+
+   This one rounds off the fractional part using the rounding mode
+   specified. */
+
+static void fp_roundint(struct fp_ext *dest, int mode)
+{
+	union fp_mant64 oldmant;
+	unsigned long mask;
+
+	if (!fp_normalize_ext(dest))
+		return;
+
+	/* infinities and zeroes */
+	if (IS_INF(dest) || IS_ZERO(dest)) 
+		return;
+
+	/* first truncate the lower bits */
+	oldmant = dest->mant;
+	switch (dest->exp) {
+	case 0 ... 0x3ffe:
+		dest->mant.m64 = 0;
+		break;
+	case 0x3fff ... 0x401e:
+		dest->mant.m32[0] &= 0xffffffffU << (0x401e - dest->exp);
+		dest->mant.m32[1] = 0;
+		if (oldmant.m64 == dest->mant.m64)
+			return;
+		break;
+	case 0x401f ... 0x403e:
+		dest->mant.m32[1] &= 0xffffffffU << (0x403e - dest->exp);
+		if (oldmant.m32[1] == dest->mant.m32[1])
+			return;
+		break;
+	default:
+		return;
+	}
+	fp_set_sr(FPSR_EXC_INEX2);
+
+	/* We might want to normalize upwards here... however, since
+	   we know that this is only called on the output of fp_fdiv,
+	   or with the input to fp_fint or fp_fintrz, and the inputs
+	   to all these functions are either normal or denormalized
+	   (no subnormals allowed!), there's really no need.
+
+	   In the case of fp_fdiv, observe that 0x80000000 / 0xffff =
+	   0xffff8000, and the same holds for 128-bit / 64-bit. (i.e. the
+	   smallest possible normal dividend and the largest possible normal
+	   divisor will still produce a normal quotient, therefore, (normal
+	   << 64) / normal is normal in all cases) */
+
+	switch (mode) {
+	case FPCR_ROUND_RN:
+		switch (dest->exp) {
+		case 0 ... 0x3ffd:
+			return;
+		case 0x3ffe:
+			/* As noted above, the input is always normal, so the
+			   guard bit (bit 63) is always set.  therefore, the
+			   only case in which we will NOT round to 1.0 is when
+			   the input is exactly 0.5. */
+			if (oldmant.m64 == (1ULL << 63))
+				return;
+			break;
+		case 0x3fff ... 0x401d:
+			mask = 1 << (0x401d - dest->exp);
+			if (!(oldmant.m32[0] & mask))
+				return;
+			if (oldmant.m32[0] & (mask << 1))
+				break;
+			if (!(oldmant.m32[0] << (dest->exp - 0x3ffd)) &&
+					!oldmant.m32[1])
+				return;
+			break;
+		case 0x401e:
+			if (!(oldmant.m32[1] >= 0))
+				return;
+			if (oldmant.m32[0] & 1)
+				break;
+			if (!(oldmant.m32[1] << 1))
+				return;
+			break;
+		case 0x401f ... 0x403d:
+			mask = 1 << (0x403d - dest->exp);
+			if (!(oldmant.m32[1] & mask))
+				return;
+			if (oldmant.m32[1] & (mask << 1))
+				break;
+			if (!(oldmant.m32[1] << (dest->exp - 0x401d)))
+				return;
+			break;
+		default:
+			return;
+		}
+		break;
+	case FPCR_ROUND_RZ:
+		return;
+	default:
+		if (dest->sign ^ (mode - FPCR_ROUND_RM))
+			break;
+		return;
+	}
+
+	switch (dest->exp) {
+	case 0 ... 0x3ffe:
+		dest->exp = 0x3fff;
+		dest->mant.m64 = 1ULL << 63;
+		break;
+	case 0x3fff ... 0x401e:
+		mask = 1 << (0x401e - dest->exp);
+		if (dest->mant.m32[0] += mask)
+			break;
+		dest->mant.m32[0] = 0x80000000;
+		dest->exp++;
+		break;
+	case 0x401f ... 0x403e:
+		mask = 1 << (0x403e - dest->exp);
+		if (dest->mant.m32[1] += mask)
+			break;
+		if (dest->mant.m32[0] += 1)
+                        break;
+		dest->mant.m32[0] = 0x80000000;
+                dest->exp++;
+		break;
+	}
+}
+
+/* modrem_kernel: Implementation of the FREM and FMOD instructions
+   (which are exactly the same, except for the rounding used on the
+   intermediate value) */
+
+static struct fp_ext *
+modrem_kernel(struct fp_ext *dest, struct fp_ext *src, int mode)
+{
+	struct fp_ext tmp;
+
+	fp_dyadic_check(dest, src);
+
+	/* Infinities and zeros */
+	if (IS_INF(dest) || IS_ZERO(src)) {
+		fp_set_nan(dest);
+		return dest;
+	}
+	if (IS_ZERO(dest) || IS_INF(src))
+		return dest;
+
+	/* FIXME: there is almost certainly a smarter way to do this */
+	fp_copy_ext(&tmp, dest);
+	fp_fdiv(&tmp, src);		/* NOTE: src might be modified */
+	fp_roundint(&tmp, mode);
+	fp_fmul(&tmp, src);
+	fp_fsub(dest, &tmp);
+
+	/* set the quotient byte */
+	fp_set_quotient((dest->mant.m64 & 0x7f) | (dest->sign << 7));
+	return dest;
+}
+
+/* fp_fmod: Implements the kernel of the FMOD instruction.
+
+   Again, the argument order is backwards.  The result, as defined in
+   the Motorola manuals, is:
+
+   fmod(src,dest) = (dest - (src * floor(dest / src))) */
+
+struct fp_ext *
+fp_fmod(struct fp_ext *dest, struct fp_ext *src)
+{
+	dprint(PINSTR, "fmod\n");
+	return modrem_kernel(dest, src, FPCR_ROUND_RZ);
+}
+
+/* fp_frem: Implements the kernel of the FREM instruction.
+
+   frem(src,dest) = (dest - (src * round(dest / src)))
+ */
+
+struct fp_ext *
+fp_frem(struct fp_ext *dest, struct fp_ext *src)
+{
+	dprint(PINSTR, "frem\n");
+	return modrem_kernel(dest, src, FPCR_ROUND_RN);
+}
+
+struct fp_ext *
+fp_fint(struct fp_ext *dest, struct fp_ext *src)
+{
+	dprint(PINSTR, "fint\n");
+
+	fp_copy_ext(dest, src);
+
+	fp_roundint(dest, FPDATA->rnd);
+
+	return dest;
+}
+
+struct fp_ext *
+fp_fintrz(struct fp_ext *dest, struct fp_ext *src)
+{
+	dprint(PINSTR, "fintrz\n");
+
+	fp_copy_ext(dest, src);
+
+	fp_roundint(dest, FPCR_ROUND_RZ);
+
+	return dest;
+}
+
+struct fp_ext *
+fp_fscale(struct fp_ext *dest, struct fp_ext *src)
+{
+	int scale, oldround;
+
+	dprint(PINSTR, "fscale\n");
+
+	fp_dyadic_check(dest, src);
+
+	/* Infinities */
+	if (IS_INF(src)) {
+		fp_set_nan(dest);
+		return dest;
+	}
+	if (IS_INF(dest))
+		return dest;
+
+	/* zeroes */
+	if (IS_ZERO(src) || IS_ZERO(dest))
+		return dest;
+
+	/* Source exponent out of range */
+	if (src->exp >= 0x400c) {
+		fp_set_ovrflw(dest);
+		return dest;
+	}
+
+	/* src must be rounded with round to zero. */
+	oldround = FPDATA->rnd;
+	FPDATA->rnd = FPCR_ROUND_RZ;
+	scale = fp_conv_ext2long(src);
+	FPDATA->rnd = oldround;
+
+	/* new exponent */
+	scale += dest->exp;
+
+	if (scale >= 0x7fff) {
+		fp_set_ovrflw(dest);
+	} else if (scale <= 0) {
+		fp_set_sr(FPSR_EXC_UNFL);
+		fp_denormalize(dest, -scale);
+	} else
+		dest->exp = scale;
+
+	return dest;
+}
+