forth: add label system to z80 assembler

This commit is contained in:
Virgil Dupras 2020-03-31 09:23:00 -04:00
parent ce6e31dda1
commit 25814c0b8b
3 changed files with 93 additions and 37 deletions

Binary file not shown.

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@ -5,8 +5,58 @@
256 /MOD SWAP
;
( A, spits an assembled byte, A,, spits an assembled word )
( To debug, change C, to .X )
: A, C, ;
: A,, SPLITB A, A, ;
( Labels are a convenient way of managing relative jump
calculations. Backward labels are easy. It is only a matter
or recording "HERE" and do subtractions. Forward labels
record the place where we should write the offset, and then
when we get to that point later on, the label records the
offset there.
To avoid using dict memory in compilation targets, we
pre-declare label variables here, which means we have a
limited number of it. For now, 4 ought to be enough. )
(sysv) L1
(sysv) L2
(sysv) L3
(sysv) L4
( There are 2 label types: backward and forward. For each
type, there are two actions: set and write. Setting a label
is declaring where it is. It has to be performed at the
label's destination. Writing a label is writing its offset
difference to the binary result. It has to be done right
after a relative jump operation. Yes, labels are only for
relative jumps.
For backward labels, set happens before write. For forward
labels, write happen before set. The write operation writes
a dummy placeholder, and then the set operation writes the
offset at that placeholder's address.
Variable actions are expected to be called with labels in
front of them. Example, "L2 FSET"
About that "1 -": z80 relative jumps record "e-2", that is,
the offset that *counts the 2 bytes of the jump itself*.
Because we set the label *after* the jump OP1 itself, that's
1 byte that is taken care of. We still need to adjust by
another byte before writing the offset.
)
: BSET H@ SWAP ! ;
: BWR @ H@ - 1 - A, ;
( same as BSET, but we need to write a placeholder )
: FWR BSET 0 A, ;
: FSET @ DUP H@ -^ 1 - SWAP C! ;
( "r" register constants )
7 CONSTANT A
0 CONSTANT B
1 CONSTANT C
@ -15,6 +65,8 @@
4 CONSTANT H
5 CONSTANT L
6 CONSTANT (HL)
( "ss" register constants )
0 CONSTANT BC
1 CONSTANT DE
2 CONSTANT HL
@ -38,6 +90,7 @@
( -- )
: OP1 CREATE C, DOES> C@ A, ;
0xeb OP1 EXDEHL,
0xd9 OP1 EXX,
0x76 OP1 HALT,
0xe9 OP1 JP(HL),
0x12 OP1 LD(DE)A,
@ -49,6 +102,19 @@
0x0f OP1 RRCA,
0x37 OP1 SCF,
( Relative jumps are a bit special. They're supposed to take
an argument, but they don't take it so they can work with
the label system. Therefore, relative jumps are an OP1 but
when you use them, you're expected to write the offset
afterwards yourself. )
0x18 OP1 JR,
0x38 OP1 JRC,
0x30 OP1 JRNC,
0x28 OP1 JRZ,
0x20 OP1 JRNZ,
0x10 OP1 DJNZ,
( r -- )
: OP1r
CREATE C,
@ -72,6 +138,7 @@
0xb0 OP1r0 ORr,
0xa8 OP1r0 XORr,
0xb8 OP1r0 CPr,
0x90 OP1r0 SUBr
( qq -- also works for ss )
: OP1qq
@ -200,7 +267,7 @@
ROT ( nn op dd )
<<4 ( nn op dd<<4 )
OR A,
SPLITB A, A,
A,,
;
0x01 OP3ddnn LDddnn,
@ -209,39 +276,27 @@
CREATE C,
DOES>
C@ A,
SPLITB A, A,
A,,
;
0xcd OP3nn CALLnn,
0xc3 OP3nn JPnn,
0x22 OP3nn LD(nn)HL,
0x2a OP3nn LDHL(nn),
: OPJR
CREATE C,
DOES>
C@ A, 2 - A,
;
0x18 OPJR JRe,
0x38 OPJR JRCe,
0x30 OPJR JRNCe,
0x28 OPJR JRZe,
0x20 OPJR JRNZe,
0x10 OPJR DJNZe,
( Specials )
( dd nn -- )
: LDdd(nn),
0xed A,
SWAP <<4 0x4b OR A,
SPLITB A, A,
A,,
;
( nn dd -- )
: LD(nn)dd,
0xed A,
<<4 0x43 OR A,
SPLITB A, A,
A,,
;
( 26 == next )

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@ -155,10 +155,10 @@ CODE NOT
A L LDrr,
H ORr,
HL 0 LDddnn,
3 JRNZe, ( skip)
JRNZ, L1 FWR ( skip )
( false, make 1 )
HL INCss,
( skip )
L1 FSET ( skip )
HL PUSHqq,
;CODE
@ -190,13 +190,13 @@ CODE *
HL ADDHLss,
E RLr,
D RLr,
6 JRNCe, ( noinc )
JRNC, 4 A, ( noinc )
BC ADDHLss,
3 JRNCe, ( noinc )
JRNC, 1 A, ( noinc )
DE INCss,
( noinc )
A DECr,
-12 JRNZe, ( loop )
JRNZ, -14 A, ( loop )
HL PUSHqq,
;CODE
@ -210,17 +210,17 @@ CODE /MOD
A B LDrr,
B 16 LDrn,
HL 0 LDddnn,
( loop )
L1 BSET ( loop )
SCF,
C RLr,
RLA,
HL ADCHLss,
DE SBCHLss,
4 JRNCe, ( skip )
JRNC, L2 FWR ( skip )
DE ADDHLss,
C DECr,
( skip )
-12 DJNZe, ( loop )
L2 FSET ( skip )
DJNZ, L1 BWR ( loop )
B A LDrr,
HL PUSHqq,
BC PUSHqq,
@ -318,9 +318,9 @@ CODE IMMED?
HL DECss,
DE 0 LDddnn,
7 (HL) BITbr,
3 JRZe, ( notset )
JRZ, L1 FWR ( notset )
DE INCss,
( notset )
L1 FSET ( notset )
DE PUSHqq,
;CODE
@ -342,15 +342,16 @@ CODE SCMP
DE POPqq,
HL POPqq,
chkPS,
( loop )
L1 BSET ( loop )
LDA(DE),
(HL) CPr,
7 JRNZe, ( not equal? break early to "end". NZ is set. )
JRNZ, L2 FWR ( not equal? break early to "end".
NZ is set. )
A ORr, ( if our char is null, stop )
HL INCss,
DE INCss,
-7 JRNZe, ( loop )
( end )
JRNZ, L1 BWR ( loop )
L2 FSET ( end )
( 40 == flagsToBC )
40 CALLnn,
BC PUSHqq,
@ -372,13 +373,13 @@ CODE (parsed)
chkPS,
( 60 == parseDecimal )
60 CALLnn,
10 JRZe, ( success )
JRZ, L1 FWR ( success )
( error )
DE 0 LDddnn,
DE PUSHqq, ( dummy )
DE PUSHqq, ( flag )
JPNEXT,
( success )
L1 FSET ( success )
DE PUSHqq,
DE 1 LDddnn,
DE PUSHqq,
@ -389,13 +390,13 @@ CODE (find)
chkPS,
( 3 == find )
3 CALLnn,
10 JRZe, ( found )
JRZ, L1 FWR ( found )
( not found )
HL PUSHqq,
DE 0 LDddnn,
DE PUSHqq,
JPNEXT,
( found )
L1 FSET ( found )
DE PUSHqq,
DE 1 LDddnn,
DE PUSHqq,
@ -406,14 +407,14 @@ CODE SCPY
chkPS,
DE HERE LDdd(nn),
B 0 LDrn,
( loop )
L1 BSET ( loop )
A (HL) LDrr,
LD(DE)A,
HL INCss,
DE INCss,
B INCr,
A ORr,
-6 JRNZe, ( loop )
JRNZ, L1 BWR ( loop )
DE A LD(dd)r
HERE DE LD(nn)dd,
;CODE