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Commit ffe6c42a authored by Geert Uytterhoeven's avatar Geert Uytterhoeven
Browse files

m68k/math-emu: Remove commented out old code 



It's been unused for ages, and contains bugs (e.g. incorrect shifts in
lsl64()).

Reported-by: default avatarJonathan Elchison <jelchison@gmail.com>
Signed-off-by: default avatarGeert Uytterhoeven <geert@linux-m68k.org>
parent b2cb9241

arch/m68k/math-emu/multi_arith.h

+0 −530
Original line number Diff line number Diff line
@@ -19,246 +19,6 @@ 
#ifndef MULTI_ARITH_H

#define MULTI_ARITH_H



#if 0	/* old code... */



/* Unsigned only, because we don't need signs to multiply and divide. */

typedef unsigned int int128[4];



/* Word order */

enum {

	MSW128,

	NMSW128,

	NLSW128,

	LSW128

};



/* big-endian */

#define LO_WORD(ll) (((unsigned int *) &ll)[1])

#define HI_WORD(ll) (((unsigned int *) &ll)[0])



/* Convenience functions to stuff various integer values into int128s */



static inline void zero128(int128 a)

{

	a[LSW128] = a[NLSW128] = a[NMSW128] = a[MSW128] = 0;

}



/* Human-readable word order in the arguments */

static inline void set128(unsigned int i3, unsigned int i2, unsigned int i1,

			  unsigned int i0, int128 a)

{

	a[LSW128] = i0;

	a[NLSW128] = i1;

	a[NMSW128] = i2;

	a[MSW128] = i3;

}



/* Convenience functions (for testing as well) */

static inline void int64_to_128(unsigned long long src, int128 dest)

{

	dest[LSW128] = (unsigned int) src;

	dest[NLSW128] = src >> 32;

	dest[NMSW128] = dest[MSW128] = 0;

}



static inline void int128_to_64(const int128 src, unsigned long long *dest)

{

	*dest = src[LSW128] | (long long) src[NLSW128] << 32;

}



static inline void put_i128(const int128 a)

{

	printk("%08x %08x %08x %08x\n", a[MSW128], a[NMSW128],

	       a[NLSW128], a[LSW128]);

}



/* Internal shifters:



   Note that these are only good for 0 < count < 32.

 */



static inline void _lsl128(unsigned int count, int128 a)

{

	a[MSW128] = (a[MSW128] << count) | (a[NMSW128] >> (32 - count));

	a[NMSW128] = (a[NMSW128] << count) | (a[NLSW128] >> (32 - count));

	a[NLSW128] = (a[NLSW128] << count) | (a[LSW128] >> (32 - count));

	a[LSW128] <<= count;

}



static inline void _lsr128(unsigned int count, int128 a)

{

	a[LSW128] = (a[LSW128] >> count) | (a[NLSW128] << (32 - count));

	a[NLSW128] = (a[NLSW128] >> count) | (a[NMSW128] << (32 - count));

	a[NMSW128] = (a[NMSW128] >> count) | (a[MSW128] << (32 - count));

	a[MSW128] >>= count;

}



/* Should be faster, one would hope */



static inline void lslone128(int128 a)

{

	asm volatile ("lsl.l #1,%0\n"

		      "roxl.l #1,%1\n"

		      "roxl.l #1,%2\n"

		      "roxl.l #1,%3\n"

		      :

		      "=d" (a[LSW128]),

		      "=d"(a[NLSW128]),

		      "=d"(a[NMSW128]),

		      "=d"(a[MSW128])

		      :

		      "0"(a[LSW128]),

		      "1"(a[NLSW128]),

		      "2"(a[NMSW128]),

		      "3"(a[MSW128]));

}



static inline void lsrone128(int128 a)

{

	asm volatile ("lsr.l #1,%0\n"

		      "roxr.l #1,%1\n"

		      "roxr.l #1,%2\n"

		      "roxr.l #1,%3\n"

		      :

		      "=d" (a[MSW128]),

		      "=d"(a[NMSW128]),

		      "=d"(a[NLSW128]),

		      "=d"(a[LSW128])

		      :

		      "0"(a[MSW128]),

		      "1"(a[NMSW128]),

		      "2"(a[NLSW128]),

		      "3"(a[LSW128]));

}



/* Generalized 128-bit shifters:



   These bit-shift to a multiple of 32, then move whole longwords.  */



static inline void lsl128(unsigned int count, int128 a)

{

	int wordcount, i;



	if (count % 32)

		_lsl128(count % 32, a);



	if (0 == (wordcount = count / 32))

		return;



	/* argh, gak, endian-sensitive */

	for (i = 0; i < 4 - wordcount; i++) {

		a[i] = a[i + wordcount];

	}

	for (i = 3; i >= 4 - wordcount; --i) {

		a[i] = 0;

	}

}



static inline void lsr128(unsigned int count, int128 a)

{

	int wordcount, i;



	if (count % 32)

		_lsr128(count % 32, a);



	if (0 == (wordcount = count / 32))

		return;



	for (i = 3; i >= wordcount; --i) {

		a[i] = a[i - wordcount];

	}

	for (i = 0; i < wordcount; i++) {

		a[i] = 0;

	}

}



static inline int orl128(int a, int128 b)

{

	b[LSW128] |= a;

}



static inline int btsthi128(const int128 a)

{

	return a[MSW128] & 0x80000000;

}



/* test bits (numbered from 0 = LSB) up to and including "top" */

static inline int bftestlo128(int top, const int128 a)

{

	int r = 0;



	if (top > 31)

		r |= a[LSW128];

	if (top > 63)

		r |= a[NLSW128];

	if (top > 95)

		r |= a[NMSW128];



	r |= a[3 - (top / 32)] & ((1 << (top % 32 + 1)) - 1);



	return (r != 0);

}



/* Aargh.  We need these because GCC is broken */

/* FIXME: do them in assembly, for goodness' sake! */

static inline void mask64(int pos, unsigned long long *mask)

{

	*mask = 0;



	if (pos < 32) {

		LO_WORD(*mask) = (1 << pos) - 1;

		return;

	}

	LO_WORD(*mask) = -1;

	HI_WORD(*mask) = (1 << (pos - 32)) - 1;

}



static inline void bset64(int pos, unsigned long long *dest)

{

	/* This conditional will be optimized away.  Thanks, GCC! */

	if (pos < 32)

		asm volatile ("bset %1,%0":"=m"

			      (LO_WORD(*dest)):"id"(pos));

	else

		asm volatile ("bset %1,%0":"=m"

			      (HI_WORD(*dest)):"id"(pos - 32));

}



static inline int btst64(int pos, unsigned long long dest)

{

	if (pos < 32)

		return (0 != (LO_WORD(dest) & (1 << pos)));

	else

		return (0 != (HI_WORD(dest) & (1 << (pos - 32))));

}



static inline void lsl64(int count, unsigned long long *dest)

{

	if (count < 32) {

		HI_WORD(*dest) = (HI_WORD(*dest) << count)

		    | (LO_WORD(*dest) >> count);

		LO_WORD(*dest) <<= count;

		return;

	}

	count -= 32;

	HI_WORD(*dest) = LO_WORD(*dest) << count;

	LO_WORD(*dest) = 0;

}



static inline void lsr64(int count, unsigned long long *dest)

{

	if (count < 32) {

		LO_WORD(*dest) = (LO_WORD(*dest) >> count)

		    | (HI_WORD(*dest) << (32 - count));

		HI_WORD(*dest) >>= count;

		return;

	}

	count -= 32;

	LO_WORD(*dest) = HI_WORD(*dest) >> count;

	HI_WORD(*dest) = 0;

}

#endif



static inline void fp_denormalize(struct fp_ext *reg, unsigned int cnt)

{

	reg->exp += cnt;
@@ -481,117 +241,6 @@ static inline void fp_dividemant(union fp_mant128 *dest, struct fp_ext *src, 
	}

}



#if 0

static inline unsigned int fp_fls128(union fp_mant128 *src)

{

	unsigned long data;

	unsigned int res, off;



	if ((data = src->m32[0]))

		off = 0;

	else if ((data = src->m32[1]))

		off = 32;

	else if ((data = src->m32[2]))

		off = 64;

	else if ((data = src->m32[3]))

		off = 96;

	else

		return 128;



	asm ("bfffo %1{#0,#32},%0" : "=d" (res) : "dm" (data));

	return res + off;

}



static inline void fp_shiftmant128(union fp_mant128 *src, int shift)

{

	unsigned long sticky;



	switch (shift) {

	case 0:

		return;

	case 1:

		asm volatile ("lsl.l #1,%0"

			: "=d" (src->m32[3]) : "0" (src->m32[3]));

		asm volatile ("roxl.l #1,%0"

			: "=d" (src->m32[2]) : "0" (src->m32[2]));

		asm volatile ("roxl.l #1,%0"

			: "=d" (src->m32[1]) : "0" (src->m32[1]));

		asm volatile ("roxl.l #1,%0"

			: "=d" (src->m32[0]) : "0" (src->m32[0]));

		return;

	case 2 ... 31:

		src->m32[0] = (src->m32[0] << shift) | (src->m32[1] >> (32 - shift));

		src->m32[1] = (src->m32[1] << shift) | (src->m32[2] >> (32 - shift));

		src->m32[2] = (src->m32[2] << shift) | (src->m32[3] >> (32 - shift));

		src->m32[3] = (src->m32[3] << shift);

		return;

	case 32 ... 63:

		shift -= 32;

		src->m32[0] = (src->m32[1] << shift) | (src->m32[2] >> (32 - shift));

		src->m32[1] = (src->m32[2] << shift) | (src->m32[3] >> (32 - shift));

		src->m32[2] = (src->m32[3] << shift);

		src->m32[3] = 0;

		return;

	case 64 ... 95:

		shift -= 64;

		src->m32[0] = (src->m32[2] << shift) | (src->m32[3] >> (32 - shift));

		src->m32[1] = (src->m32[3] << shift);

		src->m32[2] = src->m32[3] = 0;

		return;

	case 96 ... 127:

		shift -= 96;

		src->m32[0] = (src->m32[3] << shift);

		src->m32[1] = src->m32[2] = src->m32[3] = 0;

		return;

	case -31 ... -1:

		shift = -shift;

		sticky = 0;

		if (src->m32[3] << (32 - shift))

			sticky = 1;

		src->m32[3] = (src->m32[3] >> shift) | (src->m32[2] << (32 - shift)) | sticky;

		src->m32[2] = (src->m32[2] >> shift) | (src->m32[1] << (32 - shift));

		src->m32[1] = (src->m32[1] >> shift) | (src->m32[0] << (32 - shift));

		src->m32[0] = (src->m32[0] >> shift);

		return;

	case -63 ... -32:

		shift = -shift - 32;

		sticky = 0;

		if ((src->m32[2] << (32 - shift)) || src->m32[3])

			sticky = 1;

		src->m32[3] = (src->m32[2] >> shift) | (src->m32[1] << (32 - shift)) | sticky;

		src->m32[2] = (src->m32[1] >> shift) | (src->m32[0] << (32 - shift));

		src->m32[1] = (src->m32[0] >> shift);

		src->m32[0] = 0;

		return;

	case -95 ... -64:

		shift = -shift - 64;

		sticky = 0;

		if ((src->m32[1] << (32 - shift)) || src->m32[2] || src->m32[3])

			sticky = 1;

		src->m32[3] = (src->m32[1] >> shift) | (src->m32[0] << (32 - shift)) | sticky;

		src->m32[2] = (src->m32[0] >> shift);

		src->m32[1] = src->m32[0] = 0;

		return;

	case -127 ... -96:

		shift = -shift - 96;

		sticky = 0;

		if ((src->m32[0] << (32 - shift)) || src->m32[1] || src->m32[2] || src->m32[3])

			sticky = 1;

		src->m32[3] = (src->m32[0] >> shift) | sticky;

		src->m32[2] = src->m32[1] = src->m32[0] = 0;

		return;

	}



	if (shift < 0 && (src->m32[0] || src->m32[1] || src->m32[2] || src->m32[3]))

		src->m32[3] = 1;

	else

		src->m32[3] = 0;

	src->m32[2] = 0;

	src->m32[1] = 0;

	src->m32[0] = 0;

}

#endif



static inline void fp_putmant128(struct fp_ext *dest, union fp_mant128 *src,

				 int shift)

{
@@ -637,183 +286,4 @@ static inline void fp_putmant128(struct fp_ext *dest, union fp_mant128 *src, 
	}

}



#if 0 /* old code... */

static inline int fls(unsigned int a)

{

	int r;



	asm volatile ("bfffo %1{#0,#32},%0"

		      : "=d" (r) : "md" (a));

	return r;

}



/* fls = "find last set" (cf. ffs(3)) */

static inline int fls128(const int128 a)

{

	if (a[MSW128])

		return fls(a[MSW128]);

	if (a[NMSW128])

		return fls(a[NMSW128]) + 32;

	/* XXX: it probably never gets beyond this point in actual

	   use, but that's indicative of a more general problem in the

	   algorithm (i.e. as per the actual 68881 implementation, we

	   really only need at most 67 bits of precision [plus

	   overflow]) so I'm not going to fix it. */

	if (a[NLSW128])

		return fls(a[NLSW128]) + 64;

	if (a[LSW128])

		return fls(a[LSW128]) + 96;

	else

		return -1;

}



static inline int zerop128(const int128 a)

{

	return !(a[LSW128] | a[NLSW128] | a[NMSW128] | a[MSW128]);

}



static inline int nonzerop128(const int128 a)

{

	return (a[LSW128] | a[NLSW128] | a[NMSW128] | a[MSW128]);

}



/* Addition and subtraction */

/* Do these in "pure" assembly, because "extended" asm is unmanageable

   here */

static inline void add128(const int128 a, int128 b)

{

	/* rotating carry flags */

	unsigned int carry[2];



	carry[0] = a[LSW128] > (0xffffffff - b[LSW128]);

	b[LSW128] += a[LSW128];



	carry[1] = a[NLSW128] > (0xffffffff - b[NLSW128] - carry[0]);

	b[NLSW128] = a[NLSW128] + b[NLSW128] + carry[0];



	carry[0] = a[NMSW128] > (0xffffffff - b[NMSW128] - carry[1]);

	b[NMSW128] = a[NMSW128] + b[NMSW128] + carry[1];



	b[MSW128] = a[MSW128] + b[MSW128] + carry[0];

}



/* Note: assembler semantics: "b -= a" */

static inline void sub128(const int128 a, int128 b)

{

	/* rotating borrow flags */

	unsigned int borrow[2];



	borrow[0] = b[LSW128] < a[LSW128];

	b[LSW128] -= a[LSW128];



	borrow[1] = b[NLSW128] < a[NLSW128] + borrow[0];

	b[NLSW128] = b[NLSW128] - a[NLSW128] - borrow[0];



	borrow[0] = b[NMSW128] < a[NMSW128] + borrow[1];

	b[NMSW128] = b[NMSW128] - a[NMSW128] - borrow[1];



	b[MSW128] = b[MSW128] - a[MSW128] - borrow[0];

}



/* Poor man's 64-bit expanding multiply */

static inline void mul64(unsigned long long a, unsigned long long b, int128 c)

{

	unsigned long long acc;

	int128 acc128;



	zero128(acc128);

	zero128(c);



	/* first the low words */

	if (LO_WORD(a) && LO_WORD(b)) {

		acc = (long long) LO_WORD(a) * LO_WORD(b);

		c[NLSW128] = HI_WORD(acc);

		c[LSW128] = LO_WORD(acc);

	}

	/* Next the high words */

	if (HI_WORD(a) && HI_WORD(b)) {

		acc = (long long) HI_WORD(a) * HI_WORD(b);

		c[MSW128] = HI_WORD(acc);

		c[NMSW128] = LO_WORD(acc);

	}

	/* The middle words */

	if (LO_WORD(a) && HI_WORD(b)) {

		acc = (long long) LO_WORD(a) * HI_WORD(b);

		acc128[NMSW128] = HI_WORD(acc);

		acc128[NLSW128] = LO_WORD(acc);

		add128(acc128, c);

	}

	/* The first and last words */

	if (HI_WORD(a) && LO_WORD(b)) {

		acc = (long long) HI_WORD(a) * LO_WORD(b);

		acc128[NMSW128] = HI_WORD(acc);

		acc128[NLSW128] = LO_WORD(acc);

		add128(acc128, c);

	}

}



/* Note: unsigned */

static inline int cmp128(int128 a, int128 b)

{

	if (a[MSW128] < b[MSW128])

		return -1;

	if (a[MSW128] > b[MSW128])

		return 1;

	if (a[NMSW128] < b[NMSW128])

		return -1;

	if (a[NMSW128] > b[NMSW128])

		return 1;

	if (a[NLSW128] < b[NLSW128])

		return -1;

	if (a[NLSW128] > b[NLSW128])

		return 1;



	return (signed) a[LSW128] - b[LSW128];

}



inline void div128(int128 a, int128 b, int128 c)

{

	int128 mask;



	/* Algorithm:



	   Shift the divisor until it's at least as big as the

	   dividend, keeping track of the position to which we've

	   shifted it, i.e. the power of 2 which we've multiplied it

	   by.



	   Then, for this power of 2 (the mask), and every one smaller

	   than it, subtract the mask from the dividend and add it to

	   the quotient until the dividend is smaller than the raised

	   divisor.  At this point, divide the dividend and the mask

	   by 2 (i.e. shift one place to the right).  Lather, rinse,

	   and repeat, until there are no more powers of 2 left. */



	/* FIXME: needless to say, there's room for improvement here too. */



	/* Shift up */

	/* XXX: since it just has to be "at least as big", we can

	   probably eliminate this horribly wasteful loop.  I will

	   have to prove this first, though */

	set128(0, 0, 0, 1, mask);

	while (cmp128(b, a) < 0 && !btsthi128(b)) {

		lslone128(b);

		lslone128(mask);

	}



	/* Shift down */

	zero128(c);

	do {

		if (cmp128(a, b) >= 0) {

			sub128(b, a);

			add128(mask, c);

		}

		lsrone128(mask);

		lsrone128(b);

	} while (nonzerop128(mask));



	/* The remainder is in a... */

}

#endif



#endif	/* MULTI_ARITH_H */