100 lines
2.3 KiB
ArmAsm
100 lines
2.3 KiB
ArmAsm
#include <linux/linkage.h>
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.macro ARM_MOD_BODY dividend, divisor, order, spare
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#if __LINUX_ARM_ARCH__ >= 5
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clz \order, \divisor
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clz \spare, \dividend
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sub \order, \order, \spare
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mov \divisor, \divisor, lsl \order
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#else
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mov \order, #0
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@ Unless the divisor is very big, shift it up in multiples of
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@ four bits, since this is the amount of unwinding in the main
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@ division loop. Continue shifting until the divisor is
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@ larger than the dividend.
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1: cmp \divisor, #0x10000000
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cmplo \divisor, \dividend
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movlo \divisor, \divisor, lsl #4
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addlo \order, \order, #4
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blo 1b
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@ For very big divisors, we must shift it a bit at a time, or
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@ we will be in danger of overflowing.
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1: cmp \divisor, #0x80000000
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cmplo \divisor, \dividend
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movlo \divisor, \divisor, lsl #1
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addlo \order, \order, #1
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blo 1b
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#endif
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@ Perform all needed substractions to keep only the reminder.
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@ Do comparisons in batch of 4 first.
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subs \order, \order, #3 @ yes, 3 is intended here
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blt 2f
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1: cmp \dividend, \divisor
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subhs \dividend, \dividend, \divisor
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cmp \dividend, \divisor, lsr #1
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subhs \dividend, \dividend, \divisor, lsr #1
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cmp \dividend, \divisor, lsr #2
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subhs \dividend, \dividend, \divisor, lsr #2
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cmp \dividend, \divisor, lsr #3
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subhs \dividend, \dividend, \divisor, lsr #3
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cmp \dividend, #1
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mov \divisor, \divisor, lsr #4
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subges \order, \order, #4
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bge 1b
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tst \order, #3
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teqne \dividend, #0
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beq 5f
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@ Either 1, 2 or 3 comparison/substractions are left.
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2: cmn \order, #2
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blt 4f
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beq 3f
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cmp \dividend, \divisor
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subhs \dividend, \dividend, \divisor
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mov \divisor, \divisor, lsr #1
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3: cmp \dividend, \divisor
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subhs \dividend, \dividend, \divisor
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mov \divisor, \divisor, lsr #1
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4: cmp \dividend, \divisor
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subhs \dividend, \dividend, \divisor
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5:
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.endm
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.align 5
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ENTRY(__modsi3)
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cmp r1, #0
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beq Ldiv0
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rsbmi r1, r1, #0 @ loops below use unsigned.
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movs ip, r0 @ preserve sign of dividend
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rsbmi r0, r0, #0 @ if negative make positive
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subs r2, r1, #1 @ compare divisor with 1
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cmpne r0, r1 @ compare dividend with divisor
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moveq r0, #0
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tsthi r1, r2 @ see if divisor is power of 2
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andeq r0, r0, r2
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bls 10f
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ARM_MOD_BODY r0, r1, r2, r3
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10: cmp ip, #0
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rsbmi r0, r0, #0
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mov pc, lr
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ENDPROC(__modsi3)
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Ldiv0:
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str lr, [sp, #-4]!
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bl __div0
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mov r0, #0 @ About as wrong as it could be.
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ldr pc, [sp], #4
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