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umodsi3.S revision 1.1.1.3 
      1 /*===-- umodsi3.S - 32-bit unsigned integer 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 __umodsi3 (32-bit unsigned integer modulus)
     11  * function for the ARM 32-bit architecture.
     12  *
     13  *===----------------------------------------------------------------------===*/
     14 
     15 #include "../assembly.h"
     16 
     17 	.syntax unified
     18 	.text
     19 #if __ARM_ARCH_ISA_THUMB == 2
     20 	.thumb
     21 #endif
     22 
     23 @ unsigned int __umodsi3(unsigned int divident, unsigned int divisor)
     24 @   Calculate and return the remainder of the (unsigned) division.
     25 
     26 	.p2align 2
     27 #if __ARM_ARCH_ISA_THUMB == 2
     28 DEFINE_COMPILERRT_THUMB_FUNCTION(__umodsi3)
     29 #else
     30 DEFINE_COMPILERRT_FUNCTION(__umodsi3)
     31 #endif
     32 #if __ARM_ARCH_EXT_IDIV__
     33 	tst     r1, r1
     34 	beq     LOCAL_LABEL(divby0)
     35 	udiv	r2, r0, r1
     36 	mls 	r0, r2, r1, r0
     37 	bx  	lr
     38 #else
     39 	cmp	r1, #1
     40 	bcc	LOCAL_LABEL(divby0)
     41 	ITT(eq)
     42 	moveq	r0, #0
     43 	JMPc(lr, eq)
     44 	cmp	r0, r1
     45 	IT(cc)
     46 	JMPc(lr, cc)
     47 	/*
     48 	 * Implement division using binary long division algorithm.
     49 	 *
     50 	 * r0 is the numerator, r1 the denominator.
     51 	 *
     52 	 * The code before JMP computes the correct shift I, so that
     53 	 * r0 and (r1 << I) have the highest bit set in the same position.
     54 	 * At the time of JMP, ip := .Ldiv0block - 8 * I.
     55 	 * This depends on the fixed instruction size of block.
     56 	 * For ARM mode, this is 8 Bytes, for THUMB mode 10 Bytes.
     57 	 *
     58 	 * block(shift) implements the test-and-update-quotient core.
     59 	 * It assumes (r0 << shift) can be computed without overflow and
     60 	 * that (r0 << shift) < 2 * r1. The quotient is stored in r3.
     61 	 */
     62 
     63 #  ifdef __ARM_FEATURE_CLZ
     64 	clz	ip, r0
     65 	clz	r3, r1
     66 	/* r0 >= r1 implies clz(r0) <= clz(r1), so ip <= r3. */
     67 	sub	r3, r3, ip
     68 #    if __ARM_ARCH_ISA_THUMB == 2
     69 	adr	ip, LOCAL_LABEL(div0block) + 1
     70 	sub	ip, ip, r3, lsl #1
     71 #    else
     72 	adr	ip, LOCAL_LABEL(div0block)
     73 #    endif
     74 	sub	ip, ip, r3, lsl #3
     75 	bx	ip
     76 #  else
     77 #    if __ARM_ARCH_ISA_THUMB == 2
     78 #    error THUMB mode requires CLZ or UDIV
     79 #    endif
     80 	mov	r2, r0
     81 	adr	ip, LOCAL_LABEL(div0block)
     82 
     83 	lsr	r3, r2, #16
     84 	cmp	r3, r1
     85 	movhs	r2, r3
     86 	subhs	ip, ip, #(16 * 8)
     87 
     88 	lsr	r3, r2, #8
     89 	cmp	r3, r1
     90 	movhs	r2, r3
     91 	subhs	ip, ip, #(8 * 8)
     92 
     93 	lsr	r3, r2, #4
     94 	cmp	r3, r1
     95 	movhs	r2, r3
     96 	subhs	ip, #(4 * 8)
     97 
     98 	lsr	r3, r2, #2
     99 	cmp	r3, r1
    100 	movhs	r2, r3
    101 	subhs	ip, ip, #(2 * 8)
    102 
    103 	/* Last block, no need to update r2 or r3. */
    104 	cmp	r1, r2, lsr #1
    105 	subls	ip, ip, #(1 * 8)
    106 
    107 	JMP(ip)
    108 #  endif
    109 
    110 #define	IMM	#
    111 
    112 #define block(shift)                                                           \
    113 	cmp	r0, r1, lsl IMM shift;                                         \
    114 	IT(hs);                                                                \
    115 	WIDE(subhs)	r0, r0, r1, lsl IMM shift
    116 
    117 	block(31)
    118 	block(30)
    119 	block(29)
    120 	block(28)
    121 	block(27)
    122 	block(26)
    123 	block(25)
    124 	block(24)
    125 	block(23)
    126 	block(22)
    127 	block(21)
    128 	block(20)
    129 	block(19)
    130 	block(18)
    131 	block(17)
    132 	block(16)
    133 	block(15)
    134 	block(14)
    135 	block(13)
    136 	block(12)
    137 	block(11)
    138 	block(10)
    139 	block(9)
    140 	block(8)
    141 	block(7)
    142 	block(6)
    143 	block(5)
    144 	block(4)
    145 	block(3)
    146 	block(2)
    147 	block(1)
    148 LOCAL_LABEL(div0block):
    149 	block(0)
    150 	JMP(lr)
    151 #endif /* __ARM_ARCH_EXT_IDIV__ */
    152 
    153 LOCAL_LABEL(divby0):
    154 	mov	r0, #0
    155 #ifdef __ARM_EABI__
    156 	b	__aeabi_idiv0
    157 #else
    158 	JMP(lr)
    159 #endif
    160 
    161 END_COMPILERRT_FUNCTION(__umodsi3)
    162