1 /*===-- udivmodsi4.S - 32-bit unsigned integer divide and modulus ---------===// 2 * 3 * The LLVM Compiler Infrastructure 4 * 5 * This file is dual licensed under the MIT and the University of Illinois Open 6 * Source Licenses. See LICENSE.TXT for details. 7 * 8 *===----------------------------------------------------------------------===// 9 * 10 * This file implements the __udivmodsi4 (32-bit unsigned integer divide and 11 * modulus) function for the ARM 32-bit architecture. 12 * 13 *===----------------------------------------------------------------------===*/ 14 15 #include "../assembly.h" 16 17 .syntax unified 18 .text 19 20 #if __ARM_ARCH_ISA_THUMB == 2 21 .thumb 22 #endif 23 24 @ unsigned int __udivmodsi4(unsigned int divident, unsigned int divisor, 25 @ unsigned int *remainder) 26 @ Calculate the quotient and remainder of the (unsigned) division. The return 27 @ value is the quotient, the remainder is placed in the variable. 28 29 .p2align 2 30 #if __ARM_ARCH_ISA_THUMB == 2 31 DEFINE_COMPILERRT_THUMB_FUNCTION(__udivmodsi4) 32 #else 33 DEFINE_COMPILERRT_FUNCTION(__udivmodsi4) 34 #endif 35 #if __ARM_ARCH_EXT_IDIV__ 36 tst r1, r1 37 beq LOCAL_LABEL(divby0) 38 mov r3, r0 39 udiv r0, r3, r1 40 mls r1, r0, r1, r3 41 str r1, [r2] 42 bx lr 43 #else 44 cmp r1, #1 45 bcc LOCAL_LABEL(divby0) 46 beq LOCAL_LABEL(divby1) 47 cmp r0, r1 48 bcc LOCAL_LABEL(quotient0) 49 /* 50 * Implement division using binary long division algorithm. 51 * 52 * r0 is the numerator, r1 the denominator. 53 * 54 * The code before JMP computes the correct shift I, so that 55 * r0 and (r1 << I) have the highest bit set in the same position. 56 * At the time of JMP, ip := .Ldiv0block - 12 * I. 57 * This depends on the fixed instruction size of block. 58 * For ARM mode, this is 12 Bytes, for THUMB mode 14 Bytes. 59 * 60 * block(shift) implements the test-and-update-quotient core. 61 * It assumes (r0 << shift) can be computed without overflow and 62 * that (r0 << shift) < 2 * r1. The quotient is stored in r3. 63 */ 64 65 # ifdef __ARM_FEATURE_CLZ 66 clz ip, r0 67 clz r3, r1 68 /* r0 >= r1 implies clz(r0) <= clz(r1), so ip <= r3. */ 69 sub r3, r3, ip 70 # if __ARM_ARCH_ISA_THUMB == 2 71 adr ip, LOCAL_LABEL(div0block) + 1 72 sub ip, ip, r3, lsl #1 73 # else 74 adr ip, LOCAL_LABEL(div0block) 75 # endif 76 sub ip, ip, r3, lsl #2 77 sub ip, ip, r3, lsl #3 78 mov r3, #0 79 bx ip 80 # else 81 # if __ARM_ARCH_ISA_THUMB == 2 82 # error THUMB mode requires CLZ or UDIV 83 # endif 84 str r4, [sp, #-8]! 85 86 mov r4, r0 87 adr ip, LOCAL_LABEL(div0block) 88 89 lsr r3, r4, #16 90 cmp r3, r1 91 movhs r4, r3 92 subhs ip, ip, #(16 * 12) 93 94 lsr r3, r4, #8 95 cmp r3, r1 96 movhs r4, r3 97 subhs ip, ip, #(8 * 12) 98 99 lsr r3, r4, #4 100 cmp r3, r1 101 movhs r4, r3 102 subhs ip, #(4 * 12) 103 104 lsr r3, r4, #2 105 cmp r3, r1 106 movhs r4, r3 107 subhs ip, ip, #(2 * 12) 108 109 /* Last block, no need to update r3 or r4. */ 110 cmp r1, r4, lsr #1 111 subls ip, ip, #(1 * 12) 112 113 ldr r4, [sp], #8 /* restore r4, we are done with it. */ 114 mov r3, #0 115 116 JMP(ip) 117 # endif 118 119 #define IMM # 120 121 #define block(shift) \ 122 cmp r0, r1, lsl IMM shift; \ 123 ITT(hs); \ 124 WIDE(addhs) r3, r3, IMM (1 << shift); \ 125 WIDE(subhs) r0, r0, r1, lsl IMM shift 126 127 block(31) 128 block(30) 129 block(29) 130 block(28) 131 block(27) 132 block(26) 133 block(25) 134 block(24) 135 block(23) 136 block(22) 137 block(21) 138 block(20) 139 block(19) 140 block(18) 141 block(17) 142 block(16) 143 block(15) 144 block(14) 145 block(13) 146 block(12) 147 block(11) 148 block(10) 149 block(9) 150 block(8) 151 block(7) 152 block(6) 153 block(5) 154 block(4) 155 block(3) 156 block(2) 157 block(1) 158 LOCAL_LABEL(div0block): 159 block(0) 160 161 str r0, [r2] 162 mov r0, r3 163 JMP(lr) 164 165 LOCAL_LABEL(quotient0): 166 str r0, [r2] 167 mov r0, #0 168 JMP(lr) 169 170 LOCAL_LABEL(divby1): 171 mov r3, #0 172 str r3, [r2] 173 JMP(lr) 174 #endif /* __ARM_ARCH_EXT_IDIV__ */ 175 176 LOCAL_LABEL(divby0): 177 mov r0, #0 178 #ifdef __ARM_EABI__ 179 b __aeabi_idiv0 180 #else 181 JMP(lr) 182 #endif 183 184 END_COMPILERRT_FUNCTION(__udivmodsi4) 185
