1 #include <linux/linkage.h>
3 .macro ARM_DIV_BODY dividend, divisor, result, curbit
5 #if __LINUX_ARM_ARCH__ >= 5
9 sub \result, \curbit, \result
11 mov \divisor, \divisor, lsl \result
12 mov \curbit, \curbit, lsl \result
17 @ Initially shift the divisor left 3 bits if possible,
18 @ set curbit accordingly. This allows for curbit to be located
19 @ at the left end of each 4 bit nibbles in the division loop
20 @ to save one loop in most cases.
21 tst \divisor, #0xe0000000
22 moveq \divisor, \divisor, lsl #3
26 @ Unless the divisor is very big, shift it up in multiples of
27 @ four bits, since this is the amount of unwinding in the main
28 @ division loop. Continue shifting until the divisor is
29 @ larger than the dividend.
30 1: cmp \divisor, #0x10000000
31 cmplo \divisor, \dividend
32 movlo \divisor, \divisor, lsl #4
33 movlo \curbit, \curbit, lsl #4
36 @ For very big divisors, we must shift it a bit at a time, or
37 @ we will be in danger of overflowing.
38 1: cmp \divisor, #0x80000000
39 cmplo \divisor, \dividend
40 movlo \divisor, \divisor, lsl #1
41 movlo \curbit, \curbit, lsl #1
49 1: cmp \dividend, \divisor
50 subhs \dividend, \dividend, \divisor
51 orrhs \result, \result, \curbit
52 cmp \dividend, \divisor, lsr #1
53 subhs \dividend, \dividend, \divisor, lsr #1
54 orrhs \result, \result, \curbit, lsr #1
55 cmp \dividend, \divisor, lsr #2
56 subhs \dividend, \dividend, \divisor, lsr #2
57 orrhs \result, \result, \curbit, lsr #2
58 cmp \dividend, \divisor, lsr #3
59 subhs \dividend, \dividend, \divisor, lsr #3
60 orrhs \result, \result, \curbit, lsr #3
61 cmp \dividend, #0 @ Early termination?
62 movnes \curbit, \curbit, lsr #4 @ No, any more bits to do?
63 movne \divisor, \divisor, lsr #4
68 .macro ARM_DIV2_ORDER divisor, order
70 #if __LINUX_ARM_ARCH__ >= 5
73 rsb \order, \order, #31
77 cmp \divisor, #(1 << 16)
78 movhs \divisor, \divisor, lsr #16
82 cmp \divisor, #(1 << 8)
83 movhs \divisor, \divisor, lsr #8
84 addhs \order, \order, #8
86 cmp \divisor, #(1 << 4)
87 movhs \divisor, \divisor, lsr #4
88 addhs \order, \order, #4
90 cmp \divisor, #(1 << 2)
91 addhi \order, \order, #3
92 addls \order, \order, \divisor, lsr #1
103 eor ip, r0, r1 @ save the sign of the result.
105 rsbmi r1, r1, #0 @ loops below use unsigned.
106 subs r2, r1, #1 @ division by 1 or -1 ?
109 rsbmi r3, r0, #0 @ positive dividend value
112 tst r1, r2 @ divisor is power of 2 ?
115 ARM_DIV_BODY r3, r1, r0, r2
121 10: teq ip, r0 @ same sign ?
126 moveq r0, ip, asr #31
130 12: ARM_DIV2_ORDER r1, r2
141 mov r0, #0 @ About as wrong as it could be.
143 ENDPROC(__aeabi_idiv)