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Diffstat (limited to 'pk/ppe42/div64.S')
| -rw-r--r-- | pk/ppe42/div64.S | 248 |
1 files changed, 0 insertions, 248 deletions
diff --git a/pk/ppe42/div64.S b/pk/ppe42/div64.S deleted file mode 100644 index 7d4b1ffa..00000000 --- a/pk/ppe42/div64.S +++ /dev/null @@ -1,248 +0,0 @@ -//----------------------------------------------------------------------------- -// *! (C) Copyright International Business Machines Corp. 2014 -// *! All Rights Reserved -- Property of IBM -// *! *** IBM Confidential *** -//----------------------------------------------------------------------------- - -/// \file div64.S -/// \brief Unsigned 64/64 bit division -/// -/// This is IBM code, originally part of OS Open. The code has been slightly -/// modified from its original form, both to be compatible with PK and to -/// change the function prototype slightly. -/// -/// The code was provided by Matt Tyrlik in Raleigh. - -/* @#START#@ -** -** PSCN (Power Service and Control Network) -** Cage Controller OS Open Code -** -** (C) Copyright International Business Machines Corporation 2002 -** All Rights Reserved -** Licensed Material - Program Property of I B M -** Refer to copyright instructions: Form G120-2083 -** -** Module: -** div64.s -** -** Description: -** Divide 64 bit unsigned values on 32 bit CPU -** div64(uint64_t dividen, uint64_t divisor, -** uint64_t *quotient, uint64_t *remainder) -** -** Original source from: -** "The PowerPC Compiler Writer's Guide", pp62-65 by -** Steve Hoxey, Faraydon Karim, Bill Hay, Hank Warray, -** published by Warthman Associates, 240 Hamilton Avenue, -** Palo Alto, CA 94301, USA, 1996 for IBM. -** ISBN 0-9649654-0-2. -** -** This version checks for divisor equal to zero. -** -** Environment: -** OS Open (XCOFF) -** -** Linkage: -** AIX 4.3.3 -** -** @author -** Thomas Richter -** -** History: -** Date Author Description -** ----------------------------------------------------------------------------- -** 23-Sep-02 Richter Created -** -** @#END#@*/ - - .nolist -#include "pk.h" - .list - - .global_function __ppe42_udiv64 - - /* - ** Code comment notation: - ** msw = most-significant (high-order) word, i.e. bits 0..31 - ** lsw = least-significant (low-order) word, i.e. bits 32..63 - ** LZ = Leading Zeroes - ** SD = Significant Digits - ** - ** R3:R4 = Input parameter, dividend. - ** R5:R6 = Input parameter, divisor. - ** R7 = Output parameter, pointer to quotient. - ** R8 = Output parameter, pointer to remainder. - ** - ** Pointer arguments point to a uint64_t. - ** - ** Division is achieved using a shift/rotate/substract algorithsm - ** described above. - ** The registers are used as follows: - ** R3:R4 = dividend (upper 32bits:lower 32bits) - ** R5:R6 = divisor (upper 32bits:lower 32bits) - ** - ** R7:R8 = temporary 64 bit register (upper 32bits:lower 32bits) - ** count the number of leading 0s in the dividend - ** - ** Here is the description from the book. The dividend is placed - ** in the low order part of a 4 (32bit) register sequence named - ** tmp-high:tmp-low:dividend-high:dividend:low or tmp:dvd for short. - ** - ** Each iteration includes the following steps: - ** 1. Shift tmp:dvd by one bit to the left. - ** 2. Subtract the divisor from tmp. This is a 64 bit operation. - ** 3. If result is greater than or equal, place result in tmp and - ** set the low order bit of dividend - ** 4. If result is negative, do not modify tmp and - ** clear the low order bit of dividend - ** 5. If the number of iterations is less than the width of the - ** dividend, goto step 1. - ** - ** Now the algorithm can be improved by reducing the number of - ** iterations to be executed. - ** 1. Calculate the leading zeroes of the dividend. - ** 2. Calculate the leading zeroes of the divisor. - ** 3. Calculate the significant ones of the dividend. - ** 4. Calculate the significant ones of the divisor. - ** - ** Initial tmp := dvd >> (dvd.SD - dvs.SD) - ** Initial dvd := dvd << (dvd.LZ + dvs.SD) - ** Loops: dvd.SD - dvs.SD. - ** - ** Warning: Special care must be taken if dvd.LZ == dvs.LZ. The code - ** below does so by reducing the number of dvs.SD by one. This leads - ** to the loop being executed 1 more time than really necessary, - ** but avoids to check for the case when dvd.LZ == dvs.LZ. - ** This case (dvd.LZ == dvs.LZ) only checks for the number of leading - ** zeroes, but does not check if dividend is really greater than the - ** divisor. - ** Consider 16/17, both have an LZ value of 59. The code sets dvs.LZ - ** 60. This resutls in dvs.SD to 4, thus one iteration after which - ** tmp is the remainder 16. - */ - -__ppe42_udiv64: // PK - - /* push R30 & R31 onto the stack */ - stwu r1, -16(r1) - stvd r30, 8(r1) - - /* Save result pointers on volatile spare registers */ - ori r31, r8, 0 /* Save remainder address */ - ori r30, r7, 0 /* Save quotient address */ - - /* count the number of leading 0s in the dividend */ - cmpwi cr0, r3, 0 /* dvd.msw == 0? */ - cntlzw r0, r3 /* R0 = dvd.msw.LZ */ - cntlzw r9, r4 /* R9 = dvd.lsw.LZ */ - bne cr0, lab1 /* if(dvd.msw == 0) dvd.LZ = dvd.msw.LZ */ - addi r0, r9, 32 /* dvd.LZ = dvd.lsw.LZ + 32 */ -lab1: - /* count the number of leading 0s in the divisor */ - cmpwi cr0, r5, 0 /* dvd.msw == 0? */ - cntlzw r9, r5 /* R9 = dvs.msw.LZ */ - cntlzw r10, r6 /* R10 = dvs.lsw.LZ */ - bne cr0, lab2 /* if(dvs.msw == 0) dvs.LZ = dvs.msw.LZ */ - cmpwi cr0, r6, 0 /* dvd.lsw == 0? */ - beq cr0, lab10 /* dvs.msw == 0 */ - addi r9, r10, 32 /* dvs.LZ = dvs.lsw.LZ + 32 */ - -lab2: - /* Determine shift amounts to minimize the number of iterations */ - cmpw cr0, r0, r9 /* Compare dvd.LZ to dvs.LZ */ - subfic r10, r0, 64 /* R10 = dvd.SD */ - bgt cr0, lab9 /* if(dvs > dvd) quotient = 0 */ - addi r9, r9, 1 /* See comment above. ++dvs.LZ (or --dvs.SD) */ - subfic r9, r9, 64 /* R9 = dvs.SD */ - add r0, r0, r9 /* (dvd.LZ + dvs.SD) = left shift of dvd for */ - /* initial dvd */ - subf r9, r9, r10 /* (dvd.SD - dvs.SD) = right shift of dvd for */ - /* initial tmp */ - mtctr r9 /* Number of iterations = dvd.SD - dvs.SD */ - - /* R7:R8 = R3:R4 >> R9 */ - cmpwi cr0, r9, 32 /* compare R9 to 32 */ - addi r7, r9, -32 - blt cr0, lab3 /* if(R9 < 32) jump to lab3 */ - srw r8, r3, r7 /* tmp.lsw = dvd.msw >> (R9 - 32) */ - addi r7, r0, 0 /* tmp.msw = 0 */ - b lab4 - -lab3: - srw r8, r4, r9 /* R8 = dvd.lsw >> R9 */ - subfic r7, r9, 32 - slw r7,r3,r7 /* R7 = dvd.msw << 32 - R9 */ - or r8, r8,r7 /* tmp.lsw = R8 | R7 */ - srw r7,r3,r9 /* tmp.msw = dvd.msw >> R9 */ -lab4: - /* R3:R4 = R3:R4 << R0 */ - cmpwi cr0, r0, 32 /* Compare R0 to 32 */ - addic r9, r0, -32 - blt cr0, lab5 /* if(R0 < 32) jump to lab5 */ - slw r3, r4, r9 /* dvd.msw = dvd.lsw << R9 */ - addi r4, r0, 0 /* dvd.lsw = 0 */ - b lab6 - -lab5: - slw r3, r3, r0 /* r3 = dvd.msw << r0 */ - subfic r9, r0, 32 - srw r9, r4, r9 /* r9 = dvd.lsw >> 32 - r0 */ - or r3, r3, r9 /* dvd.msw = r3 | r9 */ - slw r4, r4, r0 /* dvd.lsw = dvd.lsw << r0 */ -lab6: - /* Restoring division shift and subtract loop */ - addi r10, r0, -1 /* r10 = -1 */ - addic r7, r7, 0 /* Clear carry bit before loop starts */ -lab7: - /* - ** tmp:dvd is considered one large register - ** each portion is shifted left 1 bit by adding it to itself - ** adde sums the carry from the previous and creates a new carry - */ - adde r4, r4, r4 /* Shift dvd.lsw left 1 bit */ - adde r3, r3, r3 /* Shift dvd.msw to left 1 bit */ - adde r8, r8, r8 /* Shift tmp.lsw to left 1 bit */ - adde r7, r7, r7 /* Shift tmp.msw to left 1 bit */ - subfc r0, r6, r8 /* tmp.lsw - dvs.lsw */ - subfe. r9, r5, r7 /* tmp.msw - dvs.msw */ - blt cr0, lab8 /* if(result < 0) clear carry bit */ - or r8, r0, r0 /* Move lsw */ - or r7, r9, r9 /* Move msw */ - addic r0, r10, 1 /* Set carry bit */ - -lab8: - bdnz lab7 - - /* Write quotient and remainder */ - adde r4, r4, r4 /* quo.lsw (lsb = CA) */ - adde r3, r3, r3 /* quo.msw (lsb from lsw) */ - stw r4, 4(r30) - stw r3, 0(r30) - stw r8, 4(r31) /* rem.lsw */ - stw r7, 0(r31) /* rem.msw */ - b lab11 - -lab9: - /* Qoutient is 0, divisor > dividend */ - addi r0, r0, 0 - stw r3, 0(r31) /* Store remainder */ - stw r4, 4(r31) - stw r0, 0(r30) /* Set quotient to zero */ - stw r0, 4(r30) - b lab11 - -lab10: - /* Divisor is 0 */ - addi r0, r0, -1 - stw r0, 0(r31) /* Set remainder to zero */ - stw r0, 4(r31) - stw r0, 0(r30) /* Set quotient to zero */ - stw r0, 4(r30) - -lab11: - //pop r30 & r31 from stack - lvd r30, 8(r1) - lwz r1, 0(r1) - blr - .epilogue __ppe42_udiv64 |
