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/*
* Copyright 2010, Google Inc.
*
* Brought in from coreboot uldivmod.S
*
* SPDX-License-Identifier: GPL-2.0
*/
#include <linux/linkage.h>
#include <asm/assembler.h>
/* We don't use Thumb instructions for now */
#define ARM(x...) x
#define THUMB(x...)
/*
* A, Q = r0 + (r1 << 32)
* B, R = r2 + (r3 << 32)
* A / B = Q ... R
*/
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
THUMB(
TMP .req r8
)
ENTRY(__aeabi_uldivmod)
stmfd sp!, {r4, r5, r6, r7, THUMB(TMP,) 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:
/* CLZ only exists in ARM architecture version 5 and above. */
#ifdef HAVE_CLZ
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
ARM( orrmi B_1, B_1, B_0, lsr ip )
THUMB( lsrmi TMP, B_0, ip )
THUMB( orrmi B_1, B_1, TMP )
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
ARM( orrmi C_1, C_1, C_0, lsr ip )
THUMB( lsrmi TMP, C_0, ip )
THUMB( orrmi C_1, C_1, TMP )
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
#else
@ C: current bit; D: result
mov C_0, #1
mov C_1, #0
mov D_0, #0
mov D_1, #0
L_lsl_4:
cmp B_1, #0x10000000
cmpcc B_1, A_1
cmpeq B_0, A_0
bcs L_lsl_1
@ B <<= 4
mov B_1, B_1, lsl #4
orr B_1, B_1, B_0, lsr #28
mov B_0, B_0, lsl #4
@ C <<= 4
mov C_1, C_1, lsl #4
orr C_1, C_1, C_0, lsr #28
mov C_0, C_0, lsl #4
b L_lsl_4
L_lsl_1:
cmp B_1, #0x80000000
cmpcc B_1, A_1
cmpeq B_0, A_0
bcs L_subtract
@ B <<= 1
mov B_1, B_1, lsl #1
orr B_1, B_1, B_0, lsr #31
mov B_0, B_0, lsl #1
@ C <<= 1
mov C_1, C_1, lsl #1
orr C_1, C_1, C_0, lsr #31
mov C_0, C_0, lsl #1
b L_lsl_1
#endif
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, THUMB(TMP,) 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, THUMB(TMP,) pc}
L_pow2:
#ifdef HAVE_CLZ
@ 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
ARM( orrpl A_0, A_0, A_1, lsl D_1 )
THUMB( lslpl TMP, A_1, D_1 )
THUMB( orrpl A_0, A_0, TMP )
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, THUMB(TMP,) pc}
#else
@ 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!
@ Count the leading zeroes in B.
mov D_0, #0
orrs B_0, B_0, B_0
@ If B is greater than 1 << 31, divide A and B by 1 << 32.
moveq A_0, A_1
moveq A_1, #0
moveq B_0, B_1
@ Count the remaining leading zeroes in B.
movs B_1, B_0, lsl #16
addeq D_0, #16
moveq B_0, B_0, lsr #16
tst B_0, #0xff
addeq D_0, #8
moveq B_0, B_0, lsr #8
tst B_0, #0xf
addeq D_0, #4
moveq B_0, B_0, lsr #4
tst B_0, #0x3
addeq D_0, #2
moveq B_0, B_0, lsr #2
tst B_0, #0x1
addeq D_0, #1
@ Shift A to the right by the appropriate amount.
rsb D_1, D_0, #32
mov Q_0, A_0, lsr D_0
orr Q_0, A_1, lsl D_1
mov Q_1, A_1, lsr D_0
@ Move C to R
mov R_0, C_0
mov R_1, C_1
ldmfd sp!, {r4, r5, r6, r7, THUMB(TMP,) pc}
#endif
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, THUMB(TMP,) pc}
ENDPROC(__aeabi_uldivmod)
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