ref: 518fd3ec8350a010e5ed6490e1106c66af8f4d02
dir: /sys/src/libc/alpha/divl.s/
/*
* ulong
* _udiv(ulong num, ulong den)
* {
* int i;
* ulong quo;
*
* if(den == 0)
* *(ulong*)-1 = 0;
* quo = num;
* if(quo > 1<<(32-1))
* quo = 1<<(32-1);
* for(i=0; den<quo; i++)
* den <<= 1;
* quo = 0;
* for(; i>=0; i--) {
* quo <<= 1;
* if(num >= den) {
* num -= den;
* quo |= 1;
* }
* den >>= 1;
* }
* return quo::num;
* }
*/
#define NOPROF 1
/*
* calling sequence:
* num: 8(R30)
* den: 12(R30)
* returns
* quo: 8(R30)
* rem: 12(R30)
*/
TEXT _udivmodl(SB), NOPROF, $-8
MOVQ $-1, R11
SLLQ $31, R11 /* (1<<31) in canonical form */
MOVL 8(R30), R23 /* numerator */
MOVL 12(R30), R10 /* denominator */
BNE R10, udm20
MOVQ R31, -1(R31) /* fault -- divide by zero; todo: use gentrap? */
udm20:
MOVQ R23, R12
BGE R12, udm34
MOVQ R11, R12
udm34:
MOVQ R31, R11
udm38:
CMPUGE R10, R12, R24
BNE R24, udm54
SLLL $1, R10
ADDQ $1, R11
JMP udm38
udm54:
MOVQ R31, R12
udm58:
BLT R11, udm8c
SLLL $1, R12
CMPUGE R23, R10, R24
BEQ R24, udm7c
SUBL R10, R23
OR $1, R12
udm7c:
SRLL $1, R10
SUBQ $1, R11
JMP udm58
udm8c:
MOVL R12, 8(R30) /* quotient */
MOVL R23, 12(R30) /* remainder */
RET
/*
* save working registers
* and bring in num/den parameters
*/
TEXT _unsargl(SB), NOPROF, $-8
MOVQ R10, 24(R30)
MOVQ R11, 32(R30)
MOVQ R12, 40(R30)
MOVQ R23, 48(R30)
MOVQ R24, 56(R30)
MOVL R27, 8(R30)
MOVL 72(R30), R27
MOVL R27, 12(R30)
RET
/*
* save working registers
* and bring in absolute value
* of num/den parameters
*/
TEXT _absargl(SB), NOPROF, $-8
MOVQ R10, 24(R30)
MOVQ R11, 32(R30)
MOVQ R12, 40(R30)
MOVQ R23, 48(R30)
MOVQ R24, 56(R30)
MOVL R27, 64(R30)
BGE R27, ab1
SUBL R27, R31, R27
ab1:
MOVL R27, 8(R30) /* numerator */
MOVL 72(R30), R27
BGE R27, ab2
SUBL R27, R31, R27
ab2:
MOVL R27, 12(R30) /* denominator */
RET
/*
* restore registers and
* return to original caller
* answer is in R27
*/
TEXT _retargl(SB), NOPROF, $-8
MOVQ 24(R30), R10
MOVQ 32(R30), R11
MOVQ 40(R30), R12
MOVQ 48(R30), R23
MOVQ 56(R30), R24
MOVL 0(R30), R26
ADDQ $64, R30
RET /* back to main sequence */
TEXT _divl(SB), NOPROF, $-8
SUBQ $64, R30 /* 5 reg save, 2 parameters, link */
MOVL R26, 0(R30)
JSR _absargl(SB)
JSR _udivmodl(SB)
MOVL 8(R30), R27
MOVL 64(R30), R10 /* clean up the sign */
MOVL 72(R30), R11
XOR R11, R10
BGE R10, div1
SUBL R27, R31, R27
div1:
JSR _retargl(SB)
RET /* not executed */
TEXT _divlu(SB), NOPROF, $-8
SUBQ $64, R30 /* 5 reg save, 2 parameters, link */
MOVL R26, 0(R30)
JSR _unsargl(SB)
JSR _udivmodl(SB)
MOVL 8(R30), R27
JSR _retargl(SB)
RET /* not executed */
TEXT _modl(SB), NOPROF, $-8
SUBQ $64, R30 /* 5 reg save, 2 parameters, link */
MOVL R26, 0(R30)
JSR _absargl(SB)
JSR _udivmodl(SB)
MOVL 12(R30), R27
MOVL 64(R30), R10 /* clean up the sign */
BGE R10, div2
SUBL R27, R31, R27
div2:
JSR _retargl(SB)
RET /* not executed */
TEXT _modlu(SB), NOPROF, $-8
SUBQ $64, R30 /* 5 reg save, 2 parameters, link */
MOVL R26, 0(R30)
JSR _unsargl(SB)
JSR _udivmodl(SB)
MOVL 12(R30), R27
JSR _retargl(SB)
RET /* not executed */