[openwrt.git] / target / linux / omap24xx / patches-2.6.37 / 100-optimized-arm-div.patch

---
 arch/arm/boot/compressed/lib1funcs.S |  348 +++++++++++++++++++++++++++++++++++
 1 file changed, 348 insertions(+)

--- /dev/null
+++ linux-2.6.35/arch/arm/boot/compressed/lib1funcs.S
@@ -0,0 +1,348 @@
+/*
+ * 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>
+
+
+.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)
+
+       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
+
+ENDPROC(__udivsi3)
+ENDPROC(__aeabi_uidiv)
+
+ENTRY(__umodsi3)
+
+       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
+
+ENDPROC(__umodsi3)
+
+ENTRY(__divsi3)
+ENTRY(__aeabi_idiv)
+
+       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
+
+ENDPROC(__divsi3)
+ENDPROC(__aeabi_idiv)
+
+ENTRY(__modsi3)
+
+       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
+
+ENDPROC(__modsi3)
+
+#ifdef CONFIG_AEABI
+
+ENTRY(__aeabi_uidivmod)
+
+       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
+
+ENDPROC(__aeabi_uidivmod)
+
+ENTRY(__aeabi_idivmod)
+
+       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
+
+ENDPROC(__aeabi_idivmod)
+
+#endif
+
+Ldiv0:
+
+       str     lr, [sp, #-8]!
+       bl      __div0
+       mov     r0, #0                  @ About as wrong as it could be.
+       ldr     pc, [sp], #8
+
+