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umodsi3.S revision 1.1.1.1 
      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 
     19 	.text
     20 	.p2align 2
     21 DEFINE_COMPILERRT_FUNCTION(__umodsi3)
     22 #if __ARM_ARCH_EXT_IDIV__
     23 	tst     r1, r1
     24 	beq     LOCAL_LABEL(divby0)
     25 	mov 	r3, r0
     26 	udiv	r0, r3, r1
     27 	mls 	r1, r0, r1, r3
     28 	str 	r1, [r2]
     29 	bx  	lr
     30 #else
     31 	cmp	r1, #1
     32 	bcc	LOCAL_LABEL(divby0)
     33 	moveq	r0, #0
     34 	JMPc(lr, eq)
     35 	cmp	r0, r1
     36 	JMPc(lr, cc)
     37 	/*
     38 	 * Implement division using binary long division algorithm.
     39 	 *
     40 	 * r0 is the numerator, r1 the denominator.
     41 	 *
     42 	 * The code before JMP computes the correct shift I, so that
     43 	 * r0 and (r1 << I) have the highest bit set in the same position.
     44 	 * At the time of JMP, ip := .Ldiv0block - 8 * I.
     45 	 * This depends on the fixed instruction size of block.
     46 	 *
     47 	 * block(shift) implements the test-and-update-quotient core.
     48 	 * It assumes (r0 << shift) can be computed without overflow and
     49 	 * that (r0 << shift) < 2 * r1. The quotient is stored in r3.
     50 	 */
     51 
     52 #  ifdef __ARM_FEATURE_CLZ
     53 	clz	ip, r0
     54 	clz	r3, r1
     55 	/* r0 >= r1 implies clz(r0) <= clz(r1), so ip <= r3. */
     56 	sub	r3, r3, ip
     57 	adr	ip, LOCAL_LABEL(div0block)
     58 	sub	ip, ip, r3, lsl #3
     59 	bx	ip
     60 #  else
     61 	mov	r2, r0
     62 	adr	ip, LOCAL_LABEL(div0block)
     63 
     64 	lsr	r3, r2, #16
     65 	cmp	r3, r1
     66 	movhs	r2, r3
     67 	subhs	ip, ip, #(16 * 8)
     68 
     69 	lsr	r3, r2, #8
     70 	cmp	r3, r1
     71 	movhs	r2, r3
     72 	subhs	ip, ip, #(8 * 8)
     73 
     74 	lsr	r3, r2, #4
     75 	cmp	r3, r1
     76 	movhs	r2, r3
     77 	subhs	ip, #(4 * 8)
     78 
     79 	lsr	r3, r2, #2
     80 	cmp	r3, r1
     81 	movhs	r2, r3
     82 	subhs	ip, ip, #(2 * 8)
     83 
     84 	/* Last block, no need to update r2 or r3. */
     85 	cmp	r1, r2, lsr #1
     86 	subls	ip, ip, #(1 * 8)
     87 
     88 	JMP(ip)
     89 #  endif
     90 
     91 #define	IMM	#
     92 
     93 #define block(shift) \
     94 	cmp	r0, r1, lsl IMM shift; \
     95 	subhs	r0, r0, r1, lsl IMM shift
     96 
     97 	block(31)
     98 	block(30)
     99 	block(29)
    100 	block(28)
    101 	block(27)
    102 	block(26)
    103 	block(25)
    104 	block(24)
    105 	block(23)
    106 	block(22)
    107 	block(21)
    108 	block(20)
    109 	block(19)
    110 	block(18)
    111 	block(17)
    112 	block(16)
    113 	block(15)
    114 	block(14)
    115 	block(13)
    116 	block(12)
    117 	block(11)
    118 	block(10)
    119 	block(9)
    120 	block(8)
    121 	block(7)
    122 	block(6)
    123 	block(5)
    124 	block(4)
    125 	block(3)
    126 	block(2)
    127 	block(1)
    128 LOCAL_LABEL(div0block):
    129 	block(0)
    130 	JMP(lr)
    131 #endif /* __ARM_ARCH_EXT_IDIV__ */
    132 
    133 LOCAL_LABEL(divby0):
    134 	mov	r0, #0
    135 #ifdef __ARM_EABI__
    136 	b	__aeabi_idiv0
    137 #else
    138 	JMP(lr)
    139 #endif
    140 
    141 END_COMPILERRT_FUNCTION(__umodsi3)
    142