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;;
;;=======================================================================================
;; The collection of debugging routines starts here
;;
;; 29-AUG-2015 Bernd Ulmann Initial version
;; 25-JUL-2020 Bernd Ulmann Added support for HALT, RTI, and INT
;; 07-AUG-2020 Bernd Ulmann RBRA/RSUB now displays the absolut destination addr.
;;=======================================================================================
;;
;
;***************************************************************************************
;* DBG$DISASM disassembles a single instruction pointed to by R8. R8 will be
;* incremented according to the addressing modes used in the instruction.
;*
;* R8: Contains the address of the instruction to be disassembled
;*
;* R8 WILL BE CHANGED BY THIS FUNCTION!
;***************************************************************************************
;
DBG$DISASM INCRB
RSUB IO$PUT_W_HEX, 1
MOVE R8, R0 ; Remember the address
MOVE ' ', R8 ; Print a delimiter
RSUB IO$PUTCHAR, 1
MOVE @R0++, R1 ; Fetch the instruction
MOVE R1, R8 ; Print the instruction code
RSUB IO$PUT_W_HEX, 1
MOVE ' ', R8 ; Print a delimiter
RSUB IO$PUTCHAR, 1
MOVE R1, R2 ; R1 contains the instruction
SHR 0x0009, R2 ; Get opcode * 8
AND 0x0078, R2 ; Filter out the unnecessary LSBs
CMP 0x0070, R2 ; Is it a control instruction?
RBRA _DBG$DISASM_CTRL, Z ; Yes. :-)
CMP 0x0078, R2 ; Is it a branch/subroutine call?
RBRA _DBG$DISASM_BRSU, Z ; Yes!
; Treat non-branch/subroutine calls:
MOVE _DBG$MNEMONICS, R8 ; Get address of mnemonic array
ADD R2, R8 ; Get pointer to mnemonic
RSUB IO$PUTS, 1 ; Print mnemonic
CMP 0x0070, R2 ; Is it HALT (shifted 3 to the left)?
RBRA _DBG$DISASM_EXIT, Z ; Yes, do not fetch operands
MOVE ' ', R8 ; Print a delimiter
RSUB IO$PUTCHAR, 1
RSUB _DBG$HANDLE_SOURCE, 1
RSUB _DBG$HANDLE_DEST, 1
RBRA _DBG$DISASM_EXIT, 1 ; Finished...
; Treat control instructions:
_DBG$DISASM_CTRL MOVE R1, R2 ; Determine the type of control instruction
SHR 0x0003, R2 ; Shift only three to the right as
AND 0x01F8, R2 ; each mnemonic is 8 characters long
MOVE _DBG$CTRL_MNEMONICS, R8
ADD R2, R8
RSUB IO$PUTS, 1 ; Print mnemonic
MOVE ' ', R8 ; Print a delimiter
RSUB IO$PUTCHAR, 1
CMP 0x0010, R2 ; Was the instruction INT?
RBRA _DBG$DISASM_EXIT, !Z; No, so we are finished here
RSUB _DBG$HANDLE_DEST, 1 ; Take care of the destination operand
RBRA _DBG$DISASM_EXIT, 1 ; Finished
; Treat branches and subroutine calls:
_DBG$DISASM_BRSU MOVE R1, R2 ; Determine branch/call type
SHR 0x0001, R2
AND 0x0018, R2 ; 00...00MM000, M = mode
MOVE _DBG$BRSU_MNEMONICS, R8
ADD R2, R8
RSUB IO$PUTS, 1 ; Print mnemonic
MOVE ' ', R8 ; Print a delimiter
RSUB IO$PUTCHAR, 1
RSUB _DBG$HANDLE_SOURCE, 1
MOVE R1, R2 ; Reread instruction
AND 0x0008, R2 ; Determine negation flag
RBRA _DBG$NO_NEGATE, Z ; No negation
MOVE '!', R8
RSUB IO$PUTCHAR, 1
_DBG$NO_NEGATE MOVE R1, R2 ; No side effects...
AND 0x0007, R2 ; Get condition codes
MOVE _DBG$CONDITIONCODES, R3
ADD R2, R3
MOVE @R3, R8
RSUB IO$PUTCHAR, 1 ; Print condition code
; Compute and display the destination address in case of RSUB/RBRA
MOVE R1, R2 ; Remember the instruction
AND 0xFFA0, R2 ; Check if it is RBRA/RSUB
CMP 0xFFA0, R2
RBRA _DBG$DISASM_EXIT, !Z
MOVE _DBG$REL_S, R8
RSUB IO$PUTS, 1 ; Print " ("
MOVE R0, R8 ; Get current address
MOVE @--R8, R8 ; Get relative address
ADD R0, R8 ; Add current address
RSUB IO$PUT_W_HEX, 1 ; Print address
MOVE ')', R8
RSUB IO$PUTCHAR, 1
_DBG$DISASM_EXIT RSUB IO$PUT_CRLF, 1
MOVE R0, R8 ; Restore address
DECRB
RET
_DBG$REL_S .ASCII_W " ("
;
; The following routine prints out the source operand and expects R1 to contain
; the instruction and R0 to contain the address. If the operand is R15 indirect,
; R0 will be incremented.
;
_DBG$HANDLE_SOURCE MOVE R1, R4 ; Prepare the source operand
SHR 0x0006, R4
;
; This routine does the actual operand decoding and is used for source and
; destination operands as well.
;
_DBG$HANDLE_OPERAND MOVE R4, R2 ; Extract the source operand reg.#
AND 0x003E, R2 ; Is it @R15++?
CMP 0x003E, R2
RBRA _DBG$HSRC_NO_CONST, !Z
; The source operand is @R15++, i.e. a constant:
MOVE @R0++, R8 ; Get contents of next memory cell
RSUB IO$PUT_W_HEX, 1 ; Print constant
RBRA _DBG$HSRC_EXIT, 1
; The source operand is something else:
_DBG$HSRC_NO_CONST MOVE R4, R2 ; Get instruction again
MOVE R2, R3 ; R3 holds the mode bits
AND 0x0003, R3 ; ...and only the mode bits
MOVE R3, R3 ; Is the mode == 0?
RBRA _DBG$HSRC_0, Z ; Yes -> direct mode, no '@'
MOVE '@', R8 ; Print a '@'-character
RSUB IO$PUTCHAR, 1
CMP 0x0003, R3 ; Is is @--?
RBRA _DBG$HSRC_0, !Z ; No...
MOVE _DBG$DECREMENT, R8
RSUB IO$PUTS, 1
_DBG$HSRC_0 AND 0x003C, R2 ; Get offset into register name array
MOVE _DBG$REGISTERS, R8
ADD R2, R8 ; Determine entry point
RSUB IO$PUTS, 1 ; Print register name
CMP 0x0002, R3 ; Was the mode @Rxx++?
RBRA _DBG$HSRC_EXIT, !Z ; No
MOVE _DBG$INCREMENT, R8 ; Print '++'
RSUB IO$PUTS, 1
_DBG$HSRC_EXIT MOVE ' ', R8 ; Print delimiter
RSUB IO$PUTCHAR, 1
RET
;
; The following routine uses _DBG$HANDLE_SOURCE to handle the destination parameter.
;
_DBG$HANDLE_DEST MOVE R1, R4
RBRA _DBG$HANDLE_OPERAND, 1
;
;
; All mnemonics are assumed to be eight characters long (including a 0-terminator)
_DBG$MNEMONICS .ASCII_W "MOVE "
.ASCII_W "ADD "
.ASCII_W "ADDC "
.ASCII_W "SUB "
.ASCII_W "SUBC "
.ASCII_W "SHL "
.ASCII_W "SHR "
.ASCII_W "SWAP "
.ASCII_W "NOT "
.ASCII_W "AND "
.ASCII_W "OR "
.ASCII_W "XOR "
.ASCII_W "CMP "
.ASCII_W "rsrvd "
.ASCII_W "CTRL " ; This is not really necessary
_DBG$CTRL_MNEMONICS .ASCII_W "HALT "
.ASCII_W "RTI "
.ASCII_W "INT "
.ASCII_W "INCRB "
.ASCII_W "DECRB "
.ASCII_W "BRSU " ; This also is not really necessary
_DBG$BRSU_MNEMONICS .ASCII_W "ABRA "
.ASCII_W "ASUB "
.ASCII_W "RBRA "
.ASCII_W "RSUB "
_DBG$CONDITIONCODES .ASCII_P "1XCZNVIM" ; Condition codes for branches/calls
; Register Names are expected to be four bytes long (including a 0-terminator)
_DBG$REGISTERS .ASCII_W "R0 "
.ASCII_W "R1 "
.ASCII_W "R2 "
.ASCII_W "R3 "
.ASCII_W "R4 "
.ASCII_W "R5 "
.ASCII_W "R6 "
.ASCII_W "R7 "
.ASCII_W "R8 "
.ASCII_W "R9 "
.ASCII_W "R10"
.ASCII_W "R11"
.ASCII_W "R12"
.ASCII_W "R13"
.ASCII_W "R14"
.ASCII_W "R15"
_DBG$DECREMENT .ASCII_W "--"
_DBG$INCREMENT .ASCII_W "++"
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