/*
   * linux/arch/arm/lib/lib1funcs.S: Optimized ARM division routines
   *
   * Author: Nicolas Pitre <nico@fluxnic.net>
   *   - contributed to gcc-3.4 on Sep 30, 2003
   *   - adapted for the Linux kernel on Oct 2, 2003
   */
  
  /* Copyright 1995, 1996, 1998, 1999, 2000, 2003 Free Software Foundation, Inc.
  
  This file is free software; you can redistribute it and/or modify it
  under the terms of the GNU General Public License as published by the
  Free Software Foundation; either version 2, or (at your option) any
  later version.
  
  In addition to the permissions in the GNU General Public License, the
  Free Software Foundation gives you unlimited permission to link the
  compiled version of this file into combinations with other programs,
  and to distribute those combinations without any restriction coming
  from the use of this file.  (The General Public License restrictions
  do apply in other respects; for example, they cover modification of
  the file, and distribution when not linked into a combine
  executable.)
  
  This file is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  General Public License for more details.
  
  You should have received a copy of the GNU General Public License
  along with this program; see the file COPYING.  If not, write to
  the Free Software Foundation, 59 Temple Place - Suite 330,
  Boston, MA 02111-1307, USA.  */
  
  
  #include <linux/linkage.h>
  #include <asm/assembler.h>
  #include <asm/unwind.h>
  
  .macro ARM_DIV_BODY dividend, divisor, result, curbit
  
  #if __LINUX_ARM_ARCH__ >= 5
  
  	clz	\curbit, \divisor
  	clz	\result, \dividend
  	sub	\result, \curbit, \result
  	mov	\curbit, #1
  	mov	\divisor, \divisor, lsl \result
  	mov	\curbit, \curbit, lsl \result
  	mov	\result, #0
  	
  #else
  
  	@ Initially shift the divisor left 3 bits if possible,
  	@ set curbit accordingly.  This allows for curbit to be located
  	@ at the left end of each 4 bit nibbles in the division loop
  	@ to save one loop in most cases.
  	tst	\divisor, #0xe0000000
  	moveq	\divisor, \divisor, lsl #3
  	moveq	\curbit, #8
  	movne	\curbit, #1
  
  	@ Unless the divisor is very big, shift it up in multiples of
  	@ four bits, since this is the amount of unwinding in the main
  	@ division loop.  Continue shifting until the divisor is 
  	@ larger than the dividend.
  1:	cmp	\divisor, #0x10000000
  	cmplo	\divisor, \dividend
  	movlo	\divisor, \divisor, lsl #4
  	movlo	\curbit, \curbit, lsl #4
  	blo	1b
  
  	@ For very big divisors, we must shift it a bit at a time, or
  	@ we will be in danger of overflowing.
  1:	cmp	\divisor, #0x80000000
  	cmplo	\divisor, \dividend
  	movlo	\divisor, \divisor, lsl #1
  	movlo	\curbit, \curbit, lsl #1
  	blo	1b
  
  	mov	\result, #0
  
  #endif
  
  	@ Division loop
  1:	cmp	\dividend, \divisor
  	subhs	\dividend, \dividend, \divisor
  	orrhs	\result,   \result,   \curbit
  	cmp	\dividend, \divisor,  lsr #1
  	subhs	\dividend, \dividend, \divisor, lsr #1
  	orrhs	\result,   \result,   \curbit,  lsr #1
  	cmp	\dividend, \divisor,  lsr #2
  	subhs	\dividend, \dividend, \divisor, lsr #2
  	orrhs	\result,   \result,   \curbit,  lsr #2
  	cmp	\dividend, \divisor,  lsr #3
  	subhs	\dividend, \dividend, \divisor, lsr #3
  	orrhs	\result,   \result,   \curbit,  lsr #3
  	cmp	\dividend, #0			@ Early termination?
  	movnes	\curbit,   \curbit,  lsr #4	@ No, any more bits to do?
  	movne	\divisor,  \divisor, lsr #4
  	bne	1b
  
  .endm
  
  
  .macro ARM_DIV2_ORDER divisor, order
  
  #if __LINUX_ARM_ARCH__ >= 5
  
  	clz	\order, \divisor
  	rsb	\order, \order, #31
  
  #else
  
  	cmp	\divisor, #(1 << 16)
  	movhs	\divisor, \divisor, lsr #16
  	movhs	\order, #16
  	movlo	\order, #0
  
  	cmp	\divisor, #(1 << 8)
  	movhs	\divisor, \divisor, lsr #8
  	addhs	\order, \order, #8
  
  	cmp	\divisor, #(1 << 4)
  	movhs	\divisor, \divisor, lsr #4
  	addhs	\order, \order, #4
  
  	cmp	\divisor, #(1 << 2)
  	addhi	\order, \order, #3
  	addls	\order, \order, \divisor, lsr #1
  
  #endif
  
  .endm
  
  
  .macro ARM_MOD_BODY dividend, divisor, order, spare
  
  #if __LINUX_ARM_ARCH__ >= 5
  
  	clz	\order, \divisor
  	clz	\spare, \dividend
  	sub	\order, \order, \spare
  	mov	\divisor, \divisor, lsl \order
  
  #else
  
  	mov	\order, #0
  
  	@ Unless the divisor is very big, shift it up in multiples of
  	@ four bits, since this is the amount of unwinding in the main
  	@ division loop.  Continue shifting until the divisor is 
  	@ larger than the dividend.
  1:	cmp	\divisor, #0x10000000
  	cmplo	\divisor, \dividend
  	movlo	\divisor, \divisor, lsl #4
  	addlo	\order, \order, #4
  	blo	1b
  
  	@ For very big divisors, we must shift it a bit at a time, or
  	@ we will be in danger of overflowing.
  1:	cmp	\divisor, #0x80000000
  	cmplo	\divisor, \dividend
  	movlo	\divisor, \divisor, lsl #1
  	addlo	\order, \order, #1
  	blo	1b
  
  #endif
  
  	@ Perform all needed substractions to keep only the reminder.
  	@ Do comparisons in batch of 4 first.
  	subs	\order, \order, #3		@ yes, 3 is intended here
  	blt	2f
  
  1:	cmp	\dividend, \divisor
  	subhs	\dividend, \dividend, \divisor
  	cmp	\dividend, \divisor,  lsr #1
  	subhs	\dividend, \dividend, \divisor, lsr #1
  	cmp	\dividend, \divisor,  lsr #2
  	subhs	\dividend, \dividend, \divisor, lsr #2
  	cmp	\dividend, \divisor,  lsr #3
  	subhs	\dividend, \dividend, \divisor, lsr #3
  	cmp	\dividend, #1
  	mov	\divisor, \divisor, lsr #4
  	subges	\order, \order, #4
  	bge	1b
  
  	tst	\order, #3
  	teqne	\dividend, #0
  	beq	5f
  
  	@ Either 1, 2 or 3 comparison/substractions are left.
  2:	cmn	\order, #2
  	blt	4f
  	beq	3f
  	cmp	\dividend, \divisor
  	subhs	\dividend, \dividend, \divisor
  	mov	\divisor,  \divisor,  lsr #1
  3:	cmp	\dividend, \divisor
  	subhs	\dividend, \dividend, \divisor
  	mov	\divisor,  \divisor,  lsr #1
  4:	cmp	\dividend, \divisor
  	subhs	\dividend, \dividend, \divisor
  5:
  .endm
  
  
  ENTRY(__udivsi3)
  ENTRY(__aeabi_uidiv)
  UNWIND(.fnstart)
  
  	subs	r2, r1, #1
  	moveq	pc, lr
  	bcc	Ldiv0
  	cmp	r0, r1
  	bls	11f
  	tst	r1, r2
  	beq	12f
  
  	ARM_DIV_BODY r0, r1, r2, r3
  
  	mov	r0, r2
  	mov	pc, lr
  
  11:	moveq	r0, #1
  	movne	r0, #0
  	mov	pc, lr
  
  12:	ARM_DIV2_ORDER r1, r2
  
  	mov	r0, r0, lsr r2
  	mov	pc, lr
  
  UNWIND(.fnend)
  ENDPROC(__udivsi3)
  ENDPROC(__aeabi_uidiv)
  
  ENTRY(__umodsi3)
  UNWIND(.fnstart)
  
  	subs	r2, r1, #1			@ compare divisor with 1
  	bcc	Ldiv0
  	cmpne	r0, r1				@ compare dividend with divisor
  	moveq   r0, #0
  	tsthi	r1, r2				@ see if divisor is power of 2
  	andeq	r0, r0, r2
  	movls	pc, lr
  
  	ARM_MOD_BODY r0, r1, r2, r3
  
  	mov	pc, lr
  
  UNWIND(.fnend)
  ENDPROC(__umodsi3)
  
  ENTRY(__divsi3)
  ENTRY(__aeabi_idiv)
  UNWIND(.fnstart)
  
  	cmp	r1, #0
  	eor	ip, r0, r1			@ save the sign of the result.
  	beq	Ldiv0
  	rsbmi	r1, r1, #0			@ loops below use unsigned.
  	subs	r2, r1, #1			@ division by 1 or -1 ?
  	beq	10f
  	movs	r3, r0
  	rsbmi	r3, r0, #0			@ positive dividend value
  	cmp	r3, r1
  	bls	11f
  	tst	r1, r2				@ divisor is power of 2 ?
  	beq	12f
  
  	ARM_DIV_BODY r3, r1, r0, r2
  
  	cmp	ip, #0
  	rsbmi	r0, r0, #0
  	mov	pc, lr
  
  10:	teq	ip, r0				@ same sign ?
  	rsbmi	r0, r0, #0
  	mov	pc, lr
  
  11:	movlo	r0, #0
  	moveq	r0, ip, asr #31
  	orreq	r0, r0, #1
  	mov	pc, lr
  
  12:	ARM_DIV2_ORDER r1, r2
  
  	cmp	ip, #0
  	mov	r0, r3, lsr r2
  	rsbmi	r0, r0, #0
  	mov	pc, lr
  
  UNWIND(.fnend)
  ENDPROC(__divsi3)
  ENDPROC(__aeabi_idiv)
  
  ENTRY(__modsi3)
  UNWIND(.fnstart)
  
  	cmp	r1, #0
  	beq	Ldiv0
  	rsbmi	r1, r1, #0			@ loops below use unsigned.
  	movs	ip, r0				@ preserve sign of dividend
  	rsbmi	r0, r0, #0			@ if negative make positive
  	subs	r2, r1, #1			@ compare divisor with 1
  	cmpne	r0, r1				@ compare dividend with divisor
  	moveq	r0, #0
  	tsthi	r1, r2				@ see if divisor is power of 2
  	andeq	r0, r0, r2
  	bls	10f
  
  	ARM_MOD_BODY r0, r1, r2, r3
  
  10:	cmp	ip, #0
  	rsbmi	r0, r0, #0
  	mov	pc, lr
  
  UNWIND(.fnend)
  ENDPROC(__modsi3)
  
  #ifdef CONFIG_AEABI
  
  ENTRY(__aeabi_uidivmod)
  UNWIND(.fnstart)
  UNWIND(.save {r0, r1, ip, lr}	)
  
  	stmfd	sp!, {r0, r1, ip, lr}
  	bl	__aeabi_uidiv
  	ldmfd	sp!, {r1, r2, ip, lr}
  	mul	r3, r0, r2
  	sub	r1, r1, r3
  	mov	pc, lr
  
  UNWIND(.fnend)
  ENDPROC(__aeabi_uidivmod)
  
  ENTRY(__aeabi_idivmod)
  UNWIND(.fnstart)
  UNWIND(.save {r0, r1, ip, lr}	)
  	stmfd	sp!, {r0, r1, ip, lr}
  	bl	__aeabi_idiv
  	ldmfd	sp!, {r1, r2, ip, lr}
  	mul	r3, r0, r2
  	sub	r1, r1, r3
  	mov	pc, lr
  
  UNWIND(.fnend)
  ENDPROC(__aeabi_idivmod)
  
  #endif
  
  Ldiv0:
  UNWIND(.fnstart)
  UNWIND(.pad #4)
  UNWIND(.save {lr})
  	str	lr, [sp, #-8]!
  	bl	__div0
  	mov	r0, #0			@ About as wrong as it could be.
  	ldr	pc, [sp], #8
  UNWIND(.fnend)
  ENDPROC(Ldiv0)