summaryrefslogtreecommitdiffstats
path: root/kernel/arch/powerpc/boot/div64.S
diff options
context:
space:
mode:
Diffstat (limited to 'kernel/arch/powerpc/boot/div64.S')
-rw-r--r--kernel/arch/powerpc/boot/div64.S111
1 files changed, 111 insertions, 0 deletions
diff --git a/kernel/arch/powerpc/boot/div64.S b/kernel/arch/powerpc/boot/div64.S
new file mode 100644
index 000000000..bbcb8a4cc
--- /dev/null
+++ b/kernel/arch/powerpc/boot/div64.S
@@ -0,0 +1,111 @@
+/*
+ * 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 "ppc_asm.h"
+
+ .globl __div64_32
+__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,
+ addc r9,r4,r10 # rounding up (so the estimate cannot
+ andc r11,r6,r10 # ever be too large, only too small)
+ andc r9,r9,r10
+ addze r9,r9
+ 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
+
+/*
+ * Extended precision shifts.
+ *
+ * Updated to be valid for shift counts from 0 to 63 inclusive.
+ * -- Gabriel
+ *
+ * R3/R4 has 64 bit value
+ * R5 has shift count
+ * result in R3/R4
+ *
+ * ashrdi3: arithmetic right shift (sign propagation)
+ * lshrdi3: logical right shift
+ * ashldi3: left shift
+ */
+ .globl __ashrdi3
+__ashrdi3:
+ subfic r6,r5,32
+ srw r4,r4,r5 # LSW = count > 31 ? 0 : LSW >> count
+ addi r7,r5,32 # could be xori, or addi with -32
+ slw r6,r3,r6 # t1 = count > 31 ? 0 : MSW << (32-count)
+ rlwinm r8,r7,0,32 # t3 = (count < 32) ? 32 : 0
+ sraw r7,r3,r7 # t2 = MSW >> (count-32)
+ or r4,r4,r6 # LSW |= t1
+ slw r7,r7,r8 # t2 = (count < 32) ? 0 : t2
+ sraw r3,r3,r5 # MSW = MSW >> count
+ or r4,r4,r7 # LSW |= t2
+ blr
+
+ .globl __ashldi3
+__ashldi3:
+ subfic r6,r5,32
+ slw r3,r3,r5 # MSW = count > 31 ? 0 : MSW << count
+ addi r7,r5,32 # could be xori, or addi with -32
+ srw r6,r4,r6 # t1 = count > 31 ? 0 : LSW >> (32-count)
+ slw r7,r4,r7 # t2 = count < 32 ? 0 : LSW << (count-32)
+ or r3,r3,r6 # MSW |= t1
+ slw r4,r4,r5 # LSW = LSW << count
+ or r3,r3,r7 # MSW |= t2
+ blr
+
+ .globl __lshrdi3
+__lshrdi3:
+ subfic r6,r5,32
+ srw r4,r4,r5 # LSW = count > 31 ? 0 : LSW >> count
+ addi r7,r5,32 # could be xori, or addi with -32
+ slw r6,r3,r6 # t1 = count > 31 ? 0 : MSW << (32-count)
+ srw r7,r3,r7 # t2 = count < 32 ? 0 : MSW >> (count-32)
+ or r4,r4,r6 # LSW |= t1
+ srw r3,r3,r5 # MSW = MSW >> count
+ or r4,r4,r7 # LSW |= t2
+ blr