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/*
* Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*
* Alternatively, this software may be distributed under the terms of the
* GNU General Public License ("GPL") version 2 as published by the Free
* Software Foundation.
*/
/*
* A, Q = r0 + (r1 << 32)
* B, R = r2 + (r3 << 32)
* A / B = Q ... R
*/
.text
.global __aeabi_uldivmod
.type __aeabi_uldivmod, function
.align 0
A_0 .req r0
A_1 .req r1
B_0 .req r2
B_1 .req r3
C_0 .req r4
C_1 .req r5
D_0 .req r6
D_1 .req r7
Q_0 .req r0
Q_1 .req r1
R_0 .req r2
R_1 .req r3
__aeabi_uldivmod:
stmfd sp!, {r4, r5, r6, r7, lr}
@ Test if B == 0
orrs ip, B_0, B_1 @ Z set -> B == 0
beq L_div_by_0
@ Test if B is power of 2: (B & (B - 1)) == 0
subs C_0, B_0, #1
sbc C_1, B_1, #0
tst C_0, B_0
tsteq B_1, C_1
beq L_pow2
@ Test if A_1 == B_1 == 0
orrs ip, A_1, B_1
beq L_div_32_32
L_div_64_64:
mov C_0, #1
mov C_1, #0
@ D_0 = clz A
teq A_1, #0
clz D_0, A_1
clzeq ip, A_0
addeq D_0, D_0, ip
@ D_1 = clz B
teq B_1, #0
clz D_1, B_1
clzeq ip, B_0
addeq D_1, D_1, ip
@ if clz B - clz A > 0
subs D_0, D_1, D_0
bls L_done_shift
@ B <<= (clz B - clz A)
subs D_1, D_0, #32
rsb ip, D_0, #32
movmi B_1, B_1, lsl D_0
orrmi B_1, B_1, B_0, lsr ip
movpl B_1, B_0, lsl D_1
mov B_0, B_0, lsl D_0
@ C = 1 << (clz B - clz A)
movmi C_1, C_1, lsl D_0
orrmi C_1, C_1, C_0, lsr ip
movpl C_1, C_0, lsl D_1
mov C_0, C_0, lsl D_0
L_done_shift:
mov D_0, #0
mov D_1, #0
@ C: current bit; D: result
L_subtract:
@ if A >= B
cmp A_1, B_1
cmpeq A_0, B_0
bcc L_update
@ A -= B
subs A_0, A_0, B_0
sbc A_1, A_1, B_1
@ D |= C
orr D_0, D_0, C_0
orr D_1, D_1, C_1
L_update:
@ if A == 0: break
orrs ip, A_1, A_0
beq L_exit
@ C >>= 1
movs C_1, C_1, lsr #1
movs C_0, C_0, rrx
@ if C == 0: break
orrs ip, C_1, C_0
beq L_exit
@ B >>= 1
movs B_1, B_1, lsr #1
mov B_0, B_0, rrx
b L_subtract
L_exit:
@ Note: A, B & Q, R are aliases
mov R_0, A_0
mov R_1, A_1
mov Q_0, D_0
mov Q_1, D_1
ldmfd sp!, {r4, r5, r6, r7, pc}
L_div_32_32:
@ Note: A_0 & r0 are aliases
@ Q_1 r1
mov r1, B_0
bl __aeabi_uidivmod
mov R_0, r1
mov R_1, #0
mov Q_1, #0
ldmfd sp!, {r4, r5, r6, r7, pc}
L_pow2:
@ Note: A, B and Q, R are aliases
@ R = A & (B - 1)
and C_0, A_0, C_0
and C_1, A_1, C_1
@ Q = A >> log2(B)
@ Note: B must not be 0 here!
clz D_0, B_0
add D_1, D_0, #1
rsbs D_0, D_0, #31
bpl L_1
clz D_0, B_1
rsb D_0, D_0, #31
mov A_0, A_1, lsr D_0
add D_0, D_0, #32
L_1:
movpl A_0, A_0, lsr D_0
orrpl A_0, A_0, A_1, lsl D_1
mov A_1, A_1, lsr D_0
@ Mov back C to R
mov R_0, C_0
mov R_1, C_1
ldmfd sp!, {r4, r5, r6, r7, pc}
L_div_by_0:
bl __div0
@ As wrong as it could be
mov Q_0, #0
mov Q_1, #0
mov R_0, #0
mov R_1, #0
ldmfd sp!, {r4, r5, r6, r7, pc}
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