1da177e4c3
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
195 lines
4.2 KiB
ArmAsm
195 lines
4.2 KiB
ArmAsm
/*
|
|
* arch/alpha/lib/divide.S
|
|
*
|
|
* (C) 1995 Linus Torvalds
|
|
*
|
|
* Alpha division..
|
|
*/
|
|
|
|
/*
|
|
* The alpha chip doesn't provide hardware division, so we have to do it
|
|
* by hand. The compiler expects the functions
|
|
*
|
|
* __divqu: 64-bit unsigned long divide
|
|
* __remqu: 64-bit unsigned long remainder
|
|
* __divqs/__remqs: signed 64-bit
|
|
* __divlu/__remlu: unsigned 32-bit
|
|
* __divls/__remls: signed 32-bit
|
|
*
|
|
* These are not normal C functions: instead of the normal
|
|
* calling sequence, these expect their arguments in registers
|
|
* $24 and $25, and return the result in $27. Register $28 may
|
|
* be clobbered (assembly temporary), anything else must be saved.
|
|
*
|
|
* In short: painful.
|
|
*
|
|
* This is a rather simple bit-at-a-time algorithm: it's very good
|
|
* at dividing random 64-bit numbers, but the more usual case where
|
|
* the divisor is small is handled better by the DEC algorithm
|
|
* using lookup tables. This uses much less memory, though, and is
|
|
* nicer on the cache.. Besides, I don't know the copyright status
|
|
* of the DEC code.
|
|
*/
|
|
|
|
/*
|
|
* My temporaries:
|
|
* $0 - current bit
|
|
* $1 - shifted divisor
|
|
* $2 - modulus/quotient
|
|
*
|
|
* $23 - return address
|
|
* $24 - dividend
|
|
* $25 - divisor
|
|
*
|
|
* $27 - quotient/modulus
|
|
* $28 - compare status
|
|
*/
|
|
|
|
#define halt .long 0
|
|
|
|
/*
|
|
* Select function type and registers
|
|
*/
|
|
#define mask $0
|
|
#define divisor $1
|
|
#define compare $28
|
|
#define tmp1 $3
|
|
#define tmp2 $4
|
|
|
|
#ifdef DIV
|
|
#define DIV_ONLY(x,y...) x,##y
|
|
#define MOD_ONLY(x,y...)
|
|
#define func(x) __div##x
|
|
#define modulus $2
|
|
#define quotient $27
|
|
#define GETSIGN(x) xor $24,$25,x
|
|
#define STACK 48
|
|
#else
|
|
#define DIV_ONLY(x,y...)
|
|
#define MOD_ONLY(x,y...) x,##y
|
|
#define func(x) __rem##x
|
|
#define modulus $27
|
|
#define quotient $2
|
|
#define GETSIGN(x) bis $24,$24,x
|
|
#define STACK 32
|
|
#endif
|
|
|
|
/*
|
|
* For 32-bit operations, we need to extend to 64-bit
|
|
*/
|
|
#ifdef INTSIZE
|
|
#define ufunction func(lu)
|
|
#define sfunction func(l)
|
|
#define LONGIFY(x) zapnot x,15,x
|
|
#define SLONGIFY(x) addl x,0,x
|
|
#else
|
|
#define ufunction func(qu)
|
|
#define sfunction func(q)
|
|
#define LONGIFY(x)
|
|
#define SLONGIFY(x)
|
|
#endif
|
|
|
|
.set noat
|
|
.align 3
|
|
.globl ufunction
|
|
.ent ufunction
|
|
ufunction:
|
|
subq $30,STACK,$30
|
|
.frame $30,STACK,$23
|
|
.prologue 0
|
|
|
|
7: stq $1, 0($30)
|
|
bis $25,$25,divisor
|
|
stq $2, 8($30)
|
|
bis $24,$24,modulus
|
|
stq $0,16($30)
|
|
bis $31,$31,quotient
|
|
LONGIFY(divisor)
|
|
stq tmp1,24($30)
|
|
LONGIFY(modulus)
|
|
bis $31,1,mask
|
|
DIV_ONLY(stq tmp2,32($30))
|
|
beq divisor, 9f /* div by zero */
|
|
|
|
#ifdef INTSIZE
|
|
/*
|
|
* shift divisor left, using 3-bit shifts for
|
|
* 32-bit divides as we can't overflow. Three-bit
|
|
* shifts will result in looping three times less
|
|
* here, but can result in two loops more later.
|
|
* Thus using a large shift isn't worth it (and
|
|
* s8add pairs better than a sll..)
|
|
*/
|
|
1: cmpult divisor,modulus,compare
|
|
s8addq divisor,$31,divisor
|
|
s8addq mask,$31,mask
|
|
bne compare,1b
|
|
#else
|
|
1: cmpult divisor,modulus,compare
|
|
blt divisor, 2f
|
|
addq divisor,divisor,divisor
|
|
addq mask,mask,mask
|
|
bne compare,1b
|
|
unop
|
|
#endif
|
|
|
|
/* ok, start to go right again.. */
|
|
2: DIV_ONLY(addq quotient,mask,tmp2)
|
|
srl mask,1,mask
|
|
cmpule divisor,modulus,compare
|
|
subq modulus,divisor,tmp1
|
|
DIV_ONLY(cmovne compare,tmp2,quotient)
|
|
srl divisor,1,divisor
|
|
cmovne compare,tmp1,modulus
|
|
bne mask,2b
|
|
|
|
9: ldq $1, 0($30)
|
|
ldq $2, 8($30)
|
|
ldq $0,16($30)
|
|
ldq tmp1,24($30)
|
|
DIV_ONLY(ldq tmp2,32($30))
|
|
addq $30,STACK,$30
|
|
ret $31,($23),1
|
|
.end ufunction
|
|
|
|
/*
|
|
* Uhh.. Ugly signed division. I'd rather not have it at all, but
|
|
* it's needed in some circumstances. There are different ways to
|
|
* handle this, really. This does:
|
|
* -a / b = a / -b = -(a / b)
|
|
* -a % b = -(a % b)
|
|
* a % -b = a % b
|
|
* which is probably not the best solution, but at least should
|
|
* have the property that (x/y)*y + (x%y) = x.
|
|
*/
|
|
.align 3
|
|
.globl sfunction
|
|
.ent sfunction
|
|
sfunction:
|
|
subq $30,STACK,$30
|
|
.frame $30,STACK,$23
|
|
.prologue 0
|
|
bis $24,$25,$28
|
|
SLONGIFY($28)
|
|
bge $28,7b
|
|
stq $24,0($30)
|
|
subq $31,$24,$28
|
|
stq $25,8($30)
|
|
cmovlt $24,$28,$24 /* abs($24) */
|
|
stq $23,16($30)
|
|
subq $31,$25,$28
|
|
stq tmp1,24($30)
|
|
cmovlt $25,$28,$25 /* abs($25) */
|
|
unop
|
|
bsr $23,ufunction
|
|
ldq $24,0($30)
|
|
ldq $25,8($30)
|
|
GETSIGN($28)
|
|
subq $31,$27,tmp1
|
|
SLONGIFY($28)
|
|
ldq $23,16($30)
|
|
cmovlt $28,tmp1,$27
|
|
ldq tmp1,24($30)
|
|
addq $30,STACK,$30
|
|
ret $31,($23),1
|
|
.end sfunction
|