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![Adam Buchbinder](/assets/img/avatar_default.png)
"Whether" is misspelled in various comments across the tree; this fixes them. No code changes. Signed-off-by: Adam Buchbinder <adam.buchbinder@gmail.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
219 lines
3.8 KiB
C
219 lines
3.8 KiB
C
/*
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fp_trig.c: floating-point math routines for the Linux-m68k
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floating point emulator.
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Copyright (c) 1998-1999 David Huggins-Daines / Roman Zippel.
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I hereby give permission, free of charge, to copy, modify, and
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redistribute this software, in source or binary form, provided that
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the above copyright notice and the following disclaimer are included
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in all such copies.
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THIS SOFTWARE IS PROVIDED "AS IS", WITH ABSOLUTELY NO WARRANTY, REAL
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OR IMPLIED.
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*/
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#include "fp_emu.h"
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static const struct fp_ext fp_one =
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{
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.exp = 0x3fff,
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};
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extern struct fp_ext *fp_fadd(struct fp_ext *dest, const struct fp_ext *src);
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extern struct fp_ext *fp_fdiv(struct fp_ext *dest, const struct fp_ext *src);
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struct fp_ext *
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fp_fsqrt(struct fp_ext *dest, struct fp_ext *src)
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{
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struct fp_ext tmp, src2;
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int i, exp;
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dprint(PINSTR, "fsqrt\n");
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fp_monadic_check(dest, src);
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if (IS_ZERO(dest))
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return dest;
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if (dest->sign) {
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fp_set_nan(dest);
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return dest;
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}
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if (IS_INF(dest))
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return dest;
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/*
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* sqrt(m) * 2^(p) , if e = 2*p
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* sqrt(m*2^e) =
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* sqrt(2*m) * 2^(p) , if e = 2*p + 1
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*
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* So we use the last bit of the exponent to decide whether to
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* use the m or 2*m.
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*
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* Since only the fractional part of the mantissa is stored and
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* the integer part is assumed to be one, we place a 1 or 2 into
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* the fixed point representation.
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*/
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exp = dest->exp;
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dest->exp = 0x3FFF;
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if (!(exp & 1)) /* lowest bit of exponent is set */
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dest->exp++;
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fp_copy_ext(&src2, dest);
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/*
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* The taylor row around a for sqrt(x) is:
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* sqrt(x) = sqrt(a) + 1/(2*sqrt(a))*(x-a) + R
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* With a=1 this gives:
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* sqrt(x) = 1 + 1/2*(x-1)
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* = 1/2*(1+x)
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*/
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fp_fadd(dest, &fp_one);
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dest->exp--; /* * 1/2 */
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/*
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* We now apply the newton rule to the function
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* f(x) := x^2 - r
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* which has a null point on x = sqrt(r).
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*
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* It gives:
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* x' := x - f(x)/f'(x)
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* = x - (x^2 -r)/(2*x)
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* = x - (x - r/x)/2
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* = (2*x - x + r/x)/2
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* = (x + r/x)/2
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*/
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for (i = 0; i < 9; i++) {
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fp_copy_ext(&tmp, &src2);
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fp_fdiv(&tmp, dest);
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fp_fadd(dest, &tmp);
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dest->exp--;
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}
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dest->exp += (exp - 0x3FFF) / 2;
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return dest;
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}
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struct fp_ext *
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fp_fetoxm1(struct fp_ext *dest, struct fp_ext *src)
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{
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uprint("fetoxm1\n");
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fp_monadic_check(dest, src);
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return dest;
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}
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struct fp_ext *
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fp_fetox(struct fp_ext *dest, struct fp_ext *src)
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{
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uprint("fetox\n");
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fp_monadic_check(dest, src);
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return dest;
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}
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struct fp_ext *
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fp_ftwotox(struct fp_ext *dest, struct fp_ext *src)
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{
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uprint("ftwotox\n");
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fp_monadic_check(dest, src);
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return dest;
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}
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struct fp_ext *
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fp_ftentox(struct fp_ext *dest, struct fp_ext *src)
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{
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uprint("ftentox\n");
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fp_monadic_check(dest, src);
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return dest;
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}
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struct fp_ext *
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fp_flogn(struct fp_ext *dest, struct fp_ext *src)
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{
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uprint("flogn\n");
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fp_monadic_check(dest, src);
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return dest;
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}
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struct fp_ext *
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fp_flognp1(struct fp_ext *dest, struct fp_ext *src)
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{
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uprint("flognp1\n");
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fp_monadic_check(dest, src);
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return dest;
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}
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struct fp_ext *
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fp_flog10(struct fp_ext *dest, struct fp_ext *src)
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{
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uprint("flog10\n");
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fp_monadic_check(dest, src);
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return dest;
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}
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struct fp_ext *
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fp_flog2(struct fp_ext *dest, struct fp_ext *src)
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{
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uprint("flog2\n");
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fp_monadic_check(dest, src);
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return dest;
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}
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struct fp_ext *
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fp_fgetexp(struct fp_ext *dest, struct fp_ext *src)
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{
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dprint(PINSTR, "fgetexp\n");
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fp_monadic_check(dest, src);
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if (IS_INF(dest)) {
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fp_set_nan(dest);
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return dest;
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}
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if (IS_ZERO(dest))
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return dest;
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fp_conv_long2ext(dest, (int)dest->exp - 0x3FFF);
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fp_normalize_ext(dest);
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return dest;
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}
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struct fp_ext *
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fp_fgetman(struct fp_ext *dest, struct fp_ext *src)
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{
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dprint(PINSTR, "fgetman\n");
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fp_monadic_check(dest, src);
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if (IS_ZERO(dest))
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return dest;
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if (IS_INF(dest))
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return dest;
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dest->exp = 0x3FFF;
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return dest;
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}
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