zasm: add support for "special instructions"
Let's not create complex rules for exception cases.
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@ -121,6 +121,11 @@ def main():
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a1 = eval(row[arg1index])
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a2 = eval(row[arg1index+1])
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args1 = genargs(a1)
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# special case handling
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if n == 'JP' and isinstance(a1, str) and a1 in 'xy':
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# we don't test the displacements for IX/IY because there can't be
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# any.
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args1 = args1[:1]
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if args1:
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for arg1 in args1:
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args2 = genargs(a2)
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@ -4,7 +4,7 @@
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; Number of rows in the argspec table
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ARGSPEC_TBL_CNT .equ 28
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; Number of rows in the primary instructions table
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INSTR_TBL_CNT .equ 102
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INSTR_TBL_CNT .equ 104
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; size in bytes of each row in the primary instructions table
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INSTR_TBL_ROWSIZE .equ 9
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@ -59,6 +59,10 @@ copy:
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pop bc
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ret
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callHL:
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jp (hl)
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ret
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; If string at (HL) starts with ( and ends with ), "enter" into the parens
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; (advance HL and put a null char at the end of the string) and set Z.
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; Otherwise, do nothing and reset Z.
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@ -452,6 +456,34 @@ matchPrimaryRow:
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pop hl
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ret
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; *** Special opcodes ***
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; The special upcode handling routines below all have the same signature.
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; Instruction row is at IX and we're expected to perform the same task as
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; getUpcode. The number of bytes, however, must go in C instead of A
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; No need to preserve HL, DE, BC and IX: it's handled by getUpcode already.
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; Handle like a regular "JP (IX+d)" except that we refuse any displacement: if
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; a displacement is specified, we error out.
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handleJPIX:
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ld a, 0xdd
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jr handleJPIXY
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handleJPIY:
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ld a, 0xfd
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jr handleJPIXY
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handleJPIXY:
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ld (curUpcode), a
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ld a, (curArg1+1)
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cp 0 ; numerical argument *must* be zero
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jr nz, .error
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; ok, we're good
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ld a, 0xe9 ; second upcode
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ld (curUpcode+1), a
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ld c, 2
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ret
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.error:
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xor c
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ret
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; Compute the upcode for argspec row at (DE) and arguments in curArg{1,2} and
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; writes the resulting upcode in curUpcode. A is the number if bytes written
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; to curUpcode (can be zero if something went wrong).
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@ -463,6 +495,18 @@ getUpcode:
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; First, let's go in IX mode. It's easier to deal with offsets here.
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ld ixh, d
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ld ixl, e
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; Are we a "special instruction"?
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bit 5, (ix+6)
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jr z, .normalInstr ; not set: normal instruction
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; We are a special instruction. Fetch handler (little endian, remember).
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ld l, (ix+7)
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ld h, (ix+8)
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call callHL
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; We have our result written in curUpcode and C is set.
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jp .end
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.normalInstr:
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; we begin by writing our "base upcode", which can be one or two bytes
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ld a, (ix+7) ; first upcode
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ld (curUpcode), a
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@ -738,10 +782,15 @@ argGrpABCDEHL:
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; 2 bytes for upcode (2nd byte is zero if instr is one byte)
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;
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; The displacement bit is split in 2 nibbles: lower nibble is the displacement
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; value, upper nibble is for flags. There is one flag currently, on bit 7, that
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; indicates that the numerical argument is of the 'e' type and has to be
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; decreased by 2 (djnz, jr). On bit 6, it indicates that the group argument's
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; value is to be placed on the second upcode rather than the first.
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; value, upper nibble is for flags:
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; Bit 7: indicates that the numerical argument is of the 'e' type and has to be
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; decreased by 2 (djnz, jr).
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; Bit 6: it indicates that the group argument's value is to be placed on the
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; second upcode rather than the first.
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; Bit 5: Indicates that this row is handled very specially: the next two bytes
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; aren't upcode bytes, but a routine address to call to handle this case with
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; custom code.
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instrTBl:
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.db "ADC", 0, 'A', 'l', 0, 0x8e , 0 ; ADC A, (HL)
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@ -807,6 +856,8 @@ instrTBl:
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.db "JP",0,0, 'l', 0, 0, 0xe9 , 0 ; JP (HL)
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.db "JP",0,0, 0xa, 'N', 3, 0b11000010 , 0 ; JP cc, NN
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.db "JP",0,0, 'N', 0, 0, 0xc3 , 0 ; JP NN
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.db "JP",0,0, 'x', 0,0x20 \ .dw handleJPIX ; JP (IX)
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.db "JP",0,0, 'y', 0,0x20 \ .dw handleJPIY ; JP (IY)
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.db "JR",0,0, 'n', 0,0x80, 0x18 , 0 ; JR e
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.db "JR",0,0,'C','n',0x80, 0x38 , 0 ; JR C, e
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.db "JR",0,0,'=','n',0x80, 0x30 , 0 ; JR NC, e
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