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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/ppc/lib/div64.S
downloadlinux-dev-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.xz
linux-dev-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.zip
Linux-2.6.12-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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+/*
+ * Divide a 64-bit unsigned number by a 32-bit unsigned number.
+ * This routine assumes that the top 32 bits of the dividend are
+ * non-zero to start with.
+ * On entry, r3 points to the dividend, which get overwritten with
+ * the 64-bit quotient, and r4 contains the divisor.
+ * On exit, r3 contains the remainder.
+ *
+ * Copyright (C) 2002 Paul Mackerras, IBM Corp.
+ *
+ * This program 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 of the License, or (at your option) any later version.
+ */
+#include <asm/ppc_asm.h>
+#include <asm/processor.h>
+
+_GLOBAL(__div64_32)
+ lwz r5,0(r3) # get the dividend into r5/r6
+ lwz r6,4(r3)
+ cmplw r5,r4
+ li r7,0
+ li r8,0
+ blt 1f
+ divwu r7,r5,r4 # if dividend.hi >= divisor,
+ mullw r0,r7,r4 # quotient.hi = dividend.hi / divisor
+ subf. r5,r0,r5 # dividend.hi %= divisor
+ beq 3f
+1: mr r11,r5 # here dividend.hi != 0
+ andis. r0,r5,0xc000
+ bne 2f
+ cntlzw r0,r5 # we are shifting the dividend right
+ li r10,-1 # to make it < 2^32, and shifting
+ srw r10,r10,r0 # the divisor right the same amount,
+ add r9,r4,r10 # rounding up (so the estimate cannot
+ andc r11,r6,r10 # ever be too large, only too small)
+ andc r9,r9,r10
+ or r11,r5,r11
+ rotlw r9,r9,r0
+ rotlw r11,r11,r0
+ divwu r11,r11,r9 # then we divide the shifted quantities
+2: mullw r10,r11,r4 # to get an estimate of the quotient,
+ mulhwu r9,r11,r4 # multiply the estimate by the divisor,
+ subfc r6,r10,r6 # take the product from the divisor,
+ add r8,r8,r11 # and add the estimate to the accumulated
+ subfe. r5,r9,r5 # quotient
+ bne 1b
+3: cmplw r6,r4
+ blt 4f
+ divwu r0,r6,r4 # perform the remaining 32-bit division
+ mullw r10,r0,r4 # and get the remainder
+ add r8,r8,r0
+ subf r6,r10,r6
+4: stw r7,0(r3) # return the quotient in *r3
+ stw r8,4(r3)
+ mr r3,r6 # return the remainder in r3
+ blr