1//===-- umodsi3.S - 32-bit unsigned integer modulus -----------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements the __umodsi3 (32-bit unsigned integer modulus)
10// function for the ARM 32-bit architecture.
11//
12//===----------------------------------------------------------------------===//
13
14#include "../assembly.h"
15
16 .syntax unified
17 .text
18 DEFINE_CODE_STATE
19
20@ unsigned int __umodsi3(unsigned int divident, unsigned int divisor)
21@ Calculate and return the remainder of the (unsigned) division.
22
23 .p2align 2
24DEFINE_COMPILERRT_FUNCTION(__umodsi3)
25#if __ARM_ARCH_EXT_IDIV__
26 tst r1, r1
27 beq LOCAL_LABEL(divby0)
28 udiv r2, r0, r1
29 mls r0, r2, r1, r0
30 bx lr
31#else
32 cmp r1, #1
33 bcc LOCAL_LABEL(divby0)
34 ITT(eq)
35 moveq r0, #0
36 JMPc(lr, eq)
37 cmp r0, r1
38 IT(cc)
39 JMPc(lr, cc)
40
41 // Implement division using binary long division algorithm.
42 //
43 // r0 is the numerator, r1 the denominator.
44 //
45 // The code before JMP computes the correct shift I, so that
46 // r0 and (r1 << I) have the highest bit set in the same position.
47 // At the time of JMP, ip := .Ldiv0block - 8 * I.
48 // This depends on the fixed instruction size of block.
49 // For ARM mode, this is 8 Bytes, for THUMB mode 10 Bytes.
50 //
51 // block(shift) implements the test-and-update-quotient core.
52 // It assumes (r0 << shift) can be computed without overflow and
53 // that (r0 << shift) < 2 * r1. The quotient is stored in r3.
54
55# ifdef __ARM_FEATURE_CLZ
56 clz ip, r0
57 clz r3, r1
58 // r0 >= r1 implies clz(r0) <= clz(r1), so ip <= r3.
59 sub r3, r3, ip
60# if defined(USE_THUMB_2)
61 adr ip, LOCAL_LABEL(div0block) + 1
62 sub ip, ip, r3, lsl #1
63# else
64 adr ip, LOCAL_LABEL(div0block)
65# endif
66 sub ip, ip, r3, lsl #3
67 bx ip
68# else
69# if defined(USE_THUMB_2)
70# error THUMB mode requires CLZ or UDIV
71# endif
72 mov r2, r0
73 adr ip, LOCAL_LABEL(div0block)
74
75 lsr r3, r2, #16
76 cmp r3, r1
77 movhs r2, r3
78 subhs ip, ip, #(16 * 8)
79
80 lsr r3, r2, #8
81 cmp r3, r1
82 movhs r2, r3
83 subhs ip, ip, #(8 * 8)
84
85 lsr r3, r2, #4
86 cmp r3, r1
87 movhs r2, r3
88 subhs ip, #(4 * 8)
89
90 lsr r3, r2, #2
91 cmp r3, r1
92 movhs r2, r3
93 subhs ip, ip, #(2 * 8)
94
95 // Last block, no need to update r2 or r3.
96 cmp r1, r2, lsr #1
97 subls ip, ip, #(1 * 8)
98
99 JMP(ip)
100# endif
101
102#define IMM #
103
104#define block(shift) \
105 cmp r0, r1, lsl IMM shift; \
106 IT(hs); \
107 WIDE(subhs) r0, r0, r1, lsl IMM shift
108
109 block(31)
110 block(30)
111 block(29)
112 block(28)
113 block(27)
114 block(26)
115 block(25)
116 block(24)
117 block(23)
118 block(22)
119 block(21)
120 block(20)
121 block(19)
122 block(18)
123 block(17)
124 block(16)
125 block(15)
126 block(14)
127 block(13)
128 block(12)
129 block(11)
130 block(10)
131 block(9)
132 block(8)
133 block(7)
134 block(6)
135 block(5)
136 block(4)
137 block(3)
138 block(2)
139 block(1)
140LOCAL_LABEL(div0block):
141 block(0)
142 JMP(lr)
143#endif // __ARM_ARCH_EXT_IDIV__
144
145LOCAL_LABEL(divby0):
146 mov r0, #0
147#ifdef __ARM_EABI__
148 b __aeabi_idiv0
149#else
150 JMP(lr)
151#endif
152
153END_COMPILERRT_FUNCTION(__umodsi3)
154
155NO_EXEC_STACK_DIRECTIVE
156
157

source code of compiler-rt/lib/builtins/arm/umodsi3.S