reduce stage0_monitor size by 6 bytes (toggle default zero, use mux)

The toggle can have default state of zero, and then non-zero means
second nybble is processed. That allows to skip initialization of
toggle, and save 4 bytes.

But then we cannot create value 1 with 4-byte instruction.

But we can get something out of this situation: we can initialize
R11 to 0x1101, and R15 to 0xF, and then we can get 0x1100 with MUX:
MUX R0 R15 R11 R8   ; 0x1100 = ((0x1101 & ~0xF) | (0 | 0xF))

And we will also have value 0xF in R15.
0xF is used twice as immediate thus we save another 4 bytes
by using non-immediate instructions two times

We save 6 bytes overall.
(We lose 2 bytes because we use immediate load to R15)
master
Dmitry Petukhov 3 years ago
parent 41cf0f4c58
commit c563ce3ddc
No known key found for this signature in database
GPG Key ID: 2301D26BDC15160D
  1. 2
      bootstrapping Steps.org
  2. 98
      stage0/stage0_monitor.hex0
  3. 66
      stage0/stage0_monitor.s
  4. 2
      test/SHA256SUMS

@ -37,7 +37,7 @@ gcc Linux\ Bootstrap/hex.c -o bin/hex
Then we can use it to make our bootstrap binary:
./bin/hex < stage0/stage0_monitor.hex0 > roms/stage0_monitor
Which should have the sha256sum of c9d397b195c6ba2bb4b19428d8b21e7737a32e5275f3027270d8925aec878042
Which should have the sha256sum of a551568d72804a2de6f6f94fcb507452e9d672c7638beb170dde84a9bf7fb82a
* Step 2 create a hex assembler
Now that we have a Hex monitor, we are now capable of either creating a text file (no ability to correct mistakes along the way) or any arbitrary hex program we want.

@ -14,83 +14,89 @@
## You should have received a copy of the GNU General Public License
## along with stage0. If not, see <http://www.gnu.org/licenses/>.
# :start ; offset = 0
# ;; R14 will be storing our condition
# ;;
# ;; R13 will be a stack pointer. It will be zero
# ;; on the start, and the stack grows up.
# ;; This means that when stack is used, the
# ;; first instructions of this program will be
# ;; overwritten. But because this is initialization
# ;; code, it is already not used at the time.
# ;; And the stack usage is fixed - there is only one CALL
# ;; instruction in this file
# ;;
# ;; R2 Is our holder.
# ;; It holds the first nybble of the byte till the second iteration
# ;;
# ;; R12 Is our toggle. It is initialized to zero on start.
# ;; When non-zero, it means that we are processing the second nybble
# ;;
# ;; R8 will hold zero. It is initialized to zero on start.
0D00003C # TRUE R12 ; Our toggle, set to -1 (0xFFFFFFFF)
# :start ; offset = 0
# ;; Prepare often-used values that will be held in registers
090001AC # ABS R10 R12 ; Set R10 to 1
E0002D2B1100 # LOADUI R11 0x1100 ; R11 will hold 0x1100
#
# ;; R14 will be storing our condition
# ;;
# ;; R13 will be a stack pointer. It will be zero
# ;; on the start, and the stack grows up.
# ;; This means that when stack is used, the
# ;; first instructions of this program will be
# ;; overwritten. But because this is initialization
# ;; code, it is already not used at the time.
# ;; And the stack usage is fixed - there is only one CALL
# ;; instruction in this file
# ;;
# ;; R15 Is our holder. It is initialized to zero on start.
E0002D2F000f # LOADUI R15 0xF ; Set R15 to 0xF
E0002D2B1101 # LOADUI R11 0x1101 ; R11 will hold 0x1101
# ;; Prep TAPE_01
0900040B # COPY R0 R11 ; 0x1100
01100FB8 # MUX R0 R15 R11 R8 ; 0x1100 = ((0x1101 & ~0xF) | (0 | 0xF))
42100001 # FOPEN_WRITE
# ;; Prep TAPE_02
050210BA # OR R0 R11 R10 ; 0x1101
0900040B # COPY R0 R11 ; 0x1101
42100001 # FOPEN_WRITE
# :loop ; offset = 1e
# :loop ; offset = 1c
0D000021 # FALSE R1 ; Read from tty
42100100 # FGETC ; Read a Char
E000A030000d # CMPSKIPI.NE R0 13 ; Replace all CR
E0002D20000a # LOADUI R0 10 ; WIth LF
42100200 # FPUTC ; Display the Char to User
42100200 # FPUTC
# ; Display the Char to User
# ;; Check for Ctrl-D
E000A0300004 # CMPSKIPI.NE R0 4
3C000108 # JUMP @finish
3C000104 # JUMP @finish
# ;; Check for EOF
E0002CC00102 # JUMP.NP R0 @finish
E0002CC000fe # JUMP.NP R0 @finish
# ;; Write out unprocessed byte
050211BA # OR R1 R11 R10 ; Write to TAPE_02
0900041B # COPY R1 R11 ; Write to TAPE_02
42100200 # FPUTC ; Print the Char
# ;; Convert byte to nybble
E0002D0D003a # CALLI R13 @hex ; Convert it
E0002D0D0036 # CALLI R13 @hex ; Convert it
# ;; Get another byte if nonhex
E0002CC0ffc4 # JUMP.NP R0 @loop ; Don't use nonhex chars
# ;; Deal with the case of second nybble
E0002C9C000e # JUMP.Z R12 @second_nybble ; Jump if toggled
E0002CAC000c # JUMP.NZ R12 @second_nybble ; Jump if toggled
# ;; Process first byte of pair
E100B0F0000f # ANDI R15 R0 0x0F ; Store First nibble
0D00002C # FALSE R12 ; Flip the toggle
3C00ffb0 # JUMP @loop
0502020F # AND R2 R0 R15 ; Store First nibble
0D00003C # TRUE R12 ; Flip the toggle
3C00ffb2 # JUMP @loop
# ;; Combined second nybble in pair with first
# :second_nybble ; offset = 6e
E0002D5F0004 # SL0I R15 4 ; Shift our first nibble
E100B000000f # ANDI R0 R0 0x0F ; Mask out top
0500000F # ADD R0 R0 R15 ; Combine nibbles
# :second_nybble ; offset = 6a
E0002D520004 # SL0I R2 4 ; Shift our first nibble
0502000F # AND R0 R0 R15 ; Mask out top
05000002 # ADD R0 R0 R2 ; Combine nibbles
# ;; Writeout and prepare for next cycle
0D00003C # TRUE R12 ; Flip the toggle
0D00002C # FALSE R12 ; Flip the toggle
# ; Write the combined byte
0900041B # COPY R1 R11 ; To TAPE_01
01101FB8 # MUX R1 R15 R11 R8 ; To TAPE_01
42100200 # FPUTC
3C00ff90 # JUMP @loop ; Try to get more bytes
3C00ff94 # JUMP @loop ; Try to get more bytes
# :hex ; offset = 8e
# :hex ; offset = 88
# ;; Deal with line comments starting with #
E1001FE00023 # CMPUI R14 R0 35
@ -127,37 +133,37 @@ E0002C7E000e # JUMP.LE R14 @ascii_low
# ;; Ignore the rest
3C00001e # JUMP @ascii_other
# :ascii_num ; offset = f2
# :ascii_num ; offset = ec
E10011000030 # SUBUI R0 R0 48
0D01001D # RET R13
# :ascii_low ; offset = fc
# :ascii_low ; offset = f6
E10011000057 # SUBUI R0 R0 87
0D01001D # RET R13
# :ascii_high ; offset = 106
# :ascii_high ; offset = 100
E10011000037 # SUBUI R0 R0 55
0D01001D # RET R13
# :ascii_other ; offset = 110
# :ascii_other ; offset = 10a
0D000030 # TRUE R0
0D01001D # RET R13
# :ascii_comment ; offset = 118
# :ascii_comment ; offset = 112
0D000021 # FALSE R1 ; Read from tty
42100100 # FGETC ; Read another char
E000A030000d # CMPSKIPI.NE R0 13 ; Replace all CR
E0002D20000a # LOADUI R0 10 ; WIth LF
42100200 # FPUTC ; Let the user see it
E1001FE0000a # CMPUI R14 R0 10 ; Stop at the end of line
050211BA # OR R1 R11 R10 ; Write to TAPE_02
0900041B # COPY R1 R11 ; Write to TAPE_02
42100200 # FPUTC ; The char we just read
E0002C6Effd4 # JUMP.NE R14 @ascii_comment ; Otherwise keep looping
3C00ffc8 # JUMP @ascii_other
# :finish ; offset = 148
0900040B # COPY R0 R11 ; Close TAPE_01
# :finish ; offset = 142
01100FB8 # MUX R0 R15 R11 R8 ; Close TAPE_01
42100002 # FCLOSE
050210BA # OR R0 R11 R10 ; Close TAPE_02
0900040B # COPY R0 R11 ; Close TAPE_02
42100002 # FCLOSE
FFFFFFFF # HALT

@ -14,32 +14,36 @@
; You should have received a copy of the GNU General Public License
; along with stage0. If not, see <http://www.gnu.org/licenses/>.
:start
TRUE R12 ; Our toggle, set to -1 (0xFFFFFFFF)
;; R14 will be storing our condition
;;
;; R13 will be a stack pointer. It will be zero
;; on the start, and the stack grows up.
;; This means that when stack is used, the
;; first instructions of this program will be
;; overwritten. But because this is initialization
;; code, it is already not used at the time.
;; And the stack usage is fixed - there is only one CALL
;; instruction in this file
;;
;; R2 Is our holder.
;; It holds the first nybble of the byte till the second iteration
;;
;; R12 Is our toggle. It is initialized to zero on start.
;; When non-zero, it means that we are processing the second nybble
;;
;; R8 will hold zero. It is initialized to zero on start.
:start
;; Prepare often-used values that will be held in registers
ABS R10 R12 ; Set R10 to 1
LOADUI R11 0x1100 ; R11 will hold 0x1100
;; R14 will be storing our condition
;;
;; R13 will be a stack pointer. It will be zero
;; on the start, and the stack grows up.
;; This means that when stack is used, the
;; first instructions of this program will be
;; overwritten. But because this is initialization
;; code, it is already not used at the time.
;; And the stack usage is fixed - there is only one CALL
;; instruction in this file
;;
;; R15 Is our holder. It is initialized to zero on start.
LOADUI R15 0xF ; Set R15 to 0xF
LOADUI R11 0x1101 ; R11 will hold 0x1101
;; Prep TAPE_01
COPY R0 R11 ; 0x1100
MUX R0 R15 R11 R8 ; 0x1100 = ((0x1101 & ~0xF) | (0 | 0xF))
FOPEN_WRITE
;; Prep TAPE_02
OR R0 R11 R10 ; 0x1101
COPY R0 R11 ; 0x1101
FOPEN_WRITE
:loop
@ -59,7 +63,7 @@
JUMP.NP R0 @finish
;; Write out unprocessed byte
OR R1 R11 R10 ; Write to TAPE_02
COPY R1 R11 ; Write to TAPE_02
FPUTC ; Print the Char
;; Convert byte to nybble
@ -69,23 +73,23 @@
JUMP.NP R0 @loop ; Don't use nonhex chars
;; Deal with the case of second nybble
JUMP.Z R12 @second_nybble ; Jump if toggled
JUMP.NZ R12 @second_nybble ; Jump if toggled
;; Process first byte of pair
ANDI R15 R0 0x0F ; Store First nibble
FALSE R12 ; Flip the toggle
AND R2 R0 R15 ; Store First nibble
TRUE R12 ; Flip the toggle
JUMP @loop
;; Combined second nybble in pair with first
:second_nybble
SL0I R15 4 ; Shift our first nibble
ANDI R0 R0 0x0F ; Mask out top
ADD R0 R0 R15 ; Combine nibbles
SL0I R2 4 ; Shift our first nibble
AND R0 R0 R15 ; Mask out top
ADD R0 R0 R2 ; Combine nibbles
;; Writeout and prepare for next cycle
TRUE R12 ; Flip the toggle
FALSE R12 ; Flip the toggle
; Write the combined byte
COPY R1 R11 ; To TAPE_01
MUX R1 R15 R11 R8 ; To TAPE_01
FPUTC
JUMP @loop ; Try to get more bytes
@ -136,14 +140,14 @@
LOADUI R0 10 ; WIth LF
FPUTC ; Let the user see it
CMPUI R14 R0 10 ; Stop at the end of line
OR R1 R11 R10 ; Write to TAPE_02
COPY R1 R11 ; Write to TAPE_02
FPUTC ; The char we just read
JUMP.NE R14 @ascii_comment ; Otherwise keep looping
JUMP @ascii_other
:finish
COPY R0 R11 ; Close TAPE_01
MUX R0 R15 R11 R8 ; Close TAPE_01
FCLOSE
OR R0 R11 R10 ; Close TAPE_02
COPY R0 R11 ; Close TAPE_02
FCLOSE
HALT

@ -5,7 +5,7 @@ f4bbf9e9c4828170d0c153ac265382dc705643f95efd2a029243326d426be5a4 roms/forth
2b80849180d5fb3757bcca2471b6337808e5b5ca80b18d93fa82ddef0435b84b roms/lisp
3020b194ead31ae19ba66fc35ed95465514373f6005896350d1608c9efabbdca roms/M0
059d38e34275029f2de5f600f08fe01bd13cd173f7da58e3fbec7114074beff2 roms/SET
c9d397b195c6ba2bb4b19428d8b21e7737a32e5275f3027270d8925aec878042 roms/stage0_monitor
a551568d72804a2de6f6f94fcb507452e9d672c7638beb170dde84a9bf7fb82a roms/stage0_monitor
13b45134a88c1c6db349cb40f82269cee9edfce71ac644dc0e137bad053bf5ce roms/stage1_assembler-0
156f555fce5b02f52445652b1ed0b443295706cdfbe23c5a021bd4efc77179bb roms/stage1_assembler-1
2c02c50958f489a660a4915d2a9e207a0c61f411d42628bdaf4dcf6bf7149a9d roms/stage1_assembler-2

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