diff options
Diffstat (limited to 'arch/m68k/math-emu/fp_log.c')
| -rw-r--r-- | arch/m68k/math-emu/fp_log.c | 219 |
1 files changed, 219 insertions, 0 deletions
diff --git a/arch/m68k/math-emu/fp_log.c b/arch/m68k/math-emu/fp_log.c new file mode 100644 index 000000000..066306787 --- /dev/null +++ b/arch/m68k/math-emu/fp_log.c @@ -0,0 +1,219 @@ +/* + + fp_trig.c: floating-point math routines for the Linux-m68k + floating point emulator. + + Copyright (c) 1998-1999 David Huggins-Daines / Roman Zippel. + + I hereby give permission, free of charge, to copy, modify, and + redistribute this software, in source or binary form, provided that + the above copyright notice and the following disclaimer are included + in all such copies. + + THIS SOFTWARE IS PROVIDED "AS IS", WITH ABSOLUTELY NO WARRANTY, REAL + OR IMPLIED. + +*/ + +#include "fp_emu.h" + +static const struct fp_ext fp_one = +{ + .exp = 0x3fff, +}; + +extern struct fp_ext *fp_fadd(struct fp_ext *dest, const struct fp_ext *src); +extern struct fp_ext *fp_fdiv(struct fp_ext *dest, const struct fp_ext *src); + +struct fp_ext * +fp_fsqrt(struct fp_ext *dest, struct fp_ext *src) +{ + struct fp_ext tmp, src2; + int i, exp; + + dprint(PINSTR, "fsqrt\n"); + + fp_monadic_check(dest, src); + + if (IS_ZERO(dest)) + return dest; + + if (dest->sign) { + fp_set_nan(dest); + return dest; + } + if (IS_INF(dest)) + return dest; + + /* + * sqrt(m) * 2^(p) , if e = 2*p + * sqrt(m*2^e) = + * sqrt(2*m) * 2^(p) , if e = 2*p + 1 + * + * So we use the last bit of the exponent to decide whether to + * use the m or 2*m. + * + * Since only the fractional part of the mantissa is stored and + * the integer part is assumed to be one, we place a 1 or 2 into + * the fixed point representation. + */ + exp = dest->exp; + dest->exp = 0x3FFF; + if (!(exp & 1)) /* lowest bit of exponent is set */ + dest->exp++; + fp_copy_ext(&src2, dest); + + /* + * The taylor row around a for sqrt(x) is: + * sqrt(x) = sqrt(a) + 1/(2*sqrt(a))*(x-a) + R + * With a=1 this gives: + * sqrt(x) = 1 + 1/2*(x-1) + * = 1/2*(1+x) + */ + fp_fadd(dest, &fp_one); + dest->exp--; /* * 1/2 */ + + /* + * We now apply the newton rule to the function + * f(x) := x^2 - r + * which has a null point on x = sqrt(r). + * + * It gives: + * x' := x - f(x)/f'(x) + * = x - (x^2 -r)/(2*x) + * = x - (x - r/x)/2 + * = (2*x - x + r/x)/2 + * = (x + r/x)/2 + */ + for (i = 0; i < 9; i++) { + fp_copy_ext(&tmp, &src2); + + fp_fdiv(&tmp, dest); + fp_fadd(dest, &tmp); + dest->exp--; + } + + dest->exp += (exp - 0x3FFF) / 2; + + return dest; +} + +struct fp_ext * +fp_fetoxm1(struct fp_ext *dest, struct fp_ext *src) +{ + uprint("fetoxm1\n"); + + fp_monadic_check(dest, src); + + return dest; +} + +struct fp_ext * +fp_fetox(struct fp_ext *dest, struct fp_ext *src) +{ + uprint("fetox\n"); + + fp_monadic_check(dest, src); + + return dest; +} + +struct fp_ext * +fp_ftwotox(struct fp_ext *dest, struct fp_ext *src) +{ + uprint("ftwotox\n"); + + fp_monadic_check(dest, src); + + return dest; +} + +struct fp_ext * +fp_ftentox(struct fp_ext *dest, struct fp_ext *src) +{ + uprint("ftentox\n"); + + fp_monadic_check(dest, src); + + return dest; +} + +struct fp_ext * +fp_flogn(struct fp_ext *dest, struct fp_ext *src) +{ + uprint("flogn\n"); + + fp_monadic_check(dest, src); + + return dest; +} + +struct fp_ext * +fp_flognp1(struct fp_ext *dest, struct fp_ext *src) +{ + uprint("flognp1\n"); + + fp_monadic_check(dest, src); + + return dest; +} + +struct fp_ext * +fp_flog10(struct fp_ext *dest, struct fp_ext *src) +{ + uprint("flog10\n"); + + fp_monadic_check(dest, src); + + return dest; +} + +struct fp_ext * +fp_flog2(struct fp_ext *dest, struct fp_ext *src) +{ + uprint("flog2\n"); + + fp_monadic_check(dest, src); + + return dest; +} + +struct fp_ext * +fp_fgetexp(struct fp_ext *dest, struct fp_ext *src) +{ + dprint(PINSTR, "fgetexp\n"); + + fp_monadic_check(dest, src); + + if (IS_INF(dest)) { + fp_set_nan(dest); + return dest; + } + if (IS_ZERO(dest)) + return dest; + + fp_conv_long2ext(dest, (int)dest->exp - 0x3FFF); + + fp_normalize_ext(dest); + + return dest; +} + +struct fp_ext * +fp_fgetman(struct fp_ext *dest, struct fp_ext *src) +{ + dprint(PINSTR, "fgetman\n"); + + fp_monadic_check(dest, src); + + if (IS_ZERO(dest)) + return dest; + + if (IS_INF(dest)) + return dest; + + dest->exp = 0x3FFF; + + return dest; +} + |