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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /arch/arm/lib/lib1funcs.S
downloadlinux-linaro-stable-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.gz
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
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+/*
+ * linux/arch/arm/lib/lib1funcs.S: Optimized ARM division routines
+ *
+ * Author: Nicolas Pitre <nico@cam.org>
+ * - 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)
+
+ 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
+
+
+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
+
+
+ENTRY(__divsi3)
+
+ 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
+
+
+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
+
+
+Ldiv0:
+
+ str lr, [sp, #-4]!
+ bl __div0
+ mov r0, #0 @ About as wrong as it could be.
+ ldr pc, [sp], #4
+
+