gem5 / arm / linux / 529b3ca8323e282485b7c880e4cd26eaba15934f / . / arch / m68k / fpsp040 / binstr.S

| | |

| binstr.sa 3.3 12/19/90 | |

| | |

| | |

| Description: Converts a 64-bit binary integer to bcd. | |

| | |

| Input: 64-bit binary integer in d2:d3, desired length (LEN) in | |

| d0, and a pointer to start in memory for bcd characters | |

| in d0. (This pointer must point to byte 4 of the first | |

| lword of the packed decimal memory string.) | |

| | |

| Output: LEN bcd digits representing the 64-bit integer. | |

| | |

| Algorithm: | |

| The 64-bit binary is assumed to have a decimal point before | |

| bit 63. The fraction is multiplied by 10 using a mul by 2 | |

| shift and a mul by 8 shift. The bits shifted out of the | |

| msb form a decimal digit. This process is iterated until | |

| LEN digits are formed. | |

| | |

| A1. Init d7 to 1. D7 is the byte digit counter, and if 1, the | |

| digit formed will be assumed the least significant. This is | |

| to force the first byte formed to have a 0 in the upper 4 bits. | |

| | |

| A2. Beginning of the loop: | |

| Copy the fraction in d2:d3 to d4:d5. | |

| | |

| A3. Multiply the fraction in d2:d3 by 8 using bit-field | |

| extracts and shifts. The three msbs from d2 will go into | |

| d1. | |

| | |

| A4. Multiply the fraction in d4:d5 by 2 using shifts. The msb | |

| will be collected by the carry. | |

| | |

| A5. Add using the carry the 64-bit quantities in d2:d3 and d4:d5 | |

| into d2:d3. D1 will contain the bcd digit formed. | |

| | |

| A6. Test d7. If zero, the digit formed is the ms digit. If non- | |

| zero, it is the ls digit. Put the digit in its place in the | |

| upper word of d0. If it is the ls digit, write the word | |

| from d0 to memory. | |

| | |

| A7. Decrement d6 (LEN counter) and repeat the loop until zero. | |

| | |

| Implementation Notes: | |

| | |

| The registers are used as follows: | |

| | |

| d0: LEN counter | |

| d1: temp used to form the digit | |

| d2: upper 32-bits of fraction for mul by 8 | |

| d3: lower 32-bits of fraction for mul by 8 | |

| d4: upper 32-bits of fraction for mul by 2 | |

| d5: lower 32-bits of fraction for mul by 2 | |

| d6: temp for bit-field extracts | |

| d7: byte digit formation word;digit count {0,1} | |

| a0: pointer into memory for packed bcd string formation | |

| | |

| Copyright (C) Motorola, Inc. 1990 | |

| All Rights Reserved | |

| | |

| For details on the license for this file, please see the | |

| file, README, in this same directory. | |

|BINSTR idnt 2,1 | Motorola 040 Floating Point Software Package | |

|section 8 | |

#include "fpsp.h" | |

.global binstr | |

binstr: | |

moveml %d0-%d7,-(%a7) | |

| | |

| A1: Init d7 | |

| | |

moveql #1,%d7 |init d7 for second digit | |

subql #1,%d0 |for dbf d0 would have LEN+1 passes | |

| | |

| A2. Copy d2:d3 to d4:d5. Start loop. | |

| | |

loop: | |

movel %d2,%d4 |copy the fraction before muls | |

movel %d3,%d5 |to d4:d5 | |

| | |

| A3. Multiply d2:d3 by 8; extract msbs into d1. | |

| | |

bfextu %d2{#0:#3},%d1 |copy 3 msbs of d2 into d1 | |

asll #3,%d2 |shift d2 left by 3 places | |

bfextu %d3{#0:#3},%d6 |copy 3 msbs of d3 into d6 | |

asll #3,%d3 |shift d3 left by 3 places | |

orl %d6,%d2 |or in msbs from d3 into d2 | |

| | |

| A4. Multiply d4:d5 by 2; add carry out to d1. | |

| | |

asll #1,%d5 |mul d5 by 2 | |

roxll #1,%d4 |mul d4 by 2 | |

swap %d6 |put 0 in d6 lower word | |

addxw %d6,%d1 |add in extend from mul by 2 | |

| | |

| A5. Add mul by 8 to mul by 2. D1 contains the digit formed. | |

| | |

addl %d5,%d3 |add lower 32 bits | |

nop |ERRATA ; FIX #13 (Rev. 1.2 6/6/90) | |

addxl %d4,%d2 |add with extend upper 32 bits | |

nop |ERRATA ; FIX #13 (Rev. 1.2 6/6/90) | |

addxw %d6,%d1 |add in extend from add to d1 | |

swap %d6 |with d6 = 0; put 0 in upper word | |

| | |

| A6. Test d7 and branch. | |

| | |

tstw %d7 |if zero, store digit & to loop | |

beqs first_d |if non-zero, form byte & write | |

sec_d: | |

swap %d7 |bring first digit to word d7b | |

aslw #4,%d7 |first digit in upper 4 bits d7b | |

addw %d1,%d7 |add in ls digit to d7b | |

moveb %d7,(%a0)+ |store d7b byte in memory | |

swap %d7 |put LEN counter in word d7a | |

clrw %d7 |set d7a to signal no digits done | |

dbf %d0,loop |do loop some more! | |

bras end_bstr |finished, so exit | |

first_d: | |

swap %d7 |put digit word in d7b | |

movew %d1,%d7 |put new digit in d7b | |

swap %d7 |put LEN counter in word d7a | |

addqw #1,%d7 |set d7a to signal first digit done | |

dbf %d0,loop |do loop some more! | |

swap %d7 |put last digit in string | |

lslw #4,%d7 |move it to upper 4 bits | |

moveb %d7,(%a0)+ |store it in memory string | |

| | |

| Clean up and return with result in fp0. | |

| | |

end_bstr: | |

moveml (%a7)+,%d0-%d7 | |

rts | |

|end |