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z80: Use BC as IP register instead of IY
It's a bit more inconvenient in terms of register protection (BC is much more generally useful than IY), but it makes tight spots such as next and execute much faster, so I think it's worth it.
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a7dcb522c2
commit
e4a4a9800d
4
blk/280
4
blk/280
@ -4,8 +4,8 @@ This assembles the boot binary. It requires the Z80 assembler
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(B200) and cross compilation setup (B260). It requires some
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constants to be set. See B420 for details.
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RESERVED REGISTERS: At all times, IX points to RSP TOS and IY
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is IP. SP points to PSP TOS, but you can still use the stack\
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RESERVED REGISTERS: At all times, IX points to RSP TOS and BC
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is IP. SP points to PSP TOS, but you can still use the stack
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in native code. you just have to make sure you've restored it
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before "next".
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5
blk/286
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blk/286
@ -10,7 +10,6 @@ lblnext BSET PC ORG @ 0x1b + ! ( next )
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DE RS_ADDR LDdn,
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DE SUBHLd,
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JRC, lblofl BWR ( IX < RS_ADDR? abortUnderflow-B285 )
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E 0 IY+ LDrIXY,
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D 1 IY+ LDrIXY,
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IY INCd, IY INCd,
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LDA(BC), E A LDrr, BC INCd,
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LDA(BC), D A LDrr, BC INCd,
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( continue to execute )
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7
blk/289
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blk/289
@ -2,13 +2,12 @@
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( 1. Push current IP to RS
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2. Set new IP to the second atom of the list
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3. Execute the first atom of the list. )
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IY PUSH, HL POP, ( <-- IP )
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IX INCd, IX INCd,
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0 IX+ L LDIXYr,
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1 IX+ H LDIXYr,
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0 IX+ C LDIXYr,
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1 IX+ B LDIXYr,
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EXDEHL, ( HL points to PFA )
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( While we inc, dereference into DE for execute call later. )
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LDDE(HL),
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HL INCd,
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HL PUSH, IY POP, ( --> IP )
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B H LDrr, C L LDrr, ( --> IP )
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JR, lblexec BWR ( execute-B287 )
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blk/297
8
blk/297
@ -1,9 +1,9 @@
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CODE (br)
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L1 BSET ( used in ?br and loop )
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PC ORG @ 0x3d + ! ( stable ABI JP )
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E 0 IY+ LDrIXY, D 0 LDri,
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7 E BIT, IFNZ, D DECr, THEN,
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DE ADDIYd,
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LDA(BC), H 0 LDri, L A LDrr,
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RLA, IFC, H DECr, THEN,
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BC ADDHLd, B H LDrr, C L LDrr,
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;CODE
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CODE (?br)
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PC ORG @ 0x41 + ! ( stable ABI JP )
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@ -11,5 +11,5 @@ PC ORG @ 0x41 + ! ( stable ABI JP )
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HLZ,
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JRZ, L1 BWR ( br + 1. False, branch )
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( True, skip next byte and don't branch )
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IY INCd,
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BC INCd,
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;CODE
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blk/298
2
blk/298
@ -6,7 +6,7 @@ PC ORG @ 0x45 + ! ( stable ABI JP )
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A 1 IX+ LDrIXY, 1 IX- CP(IXY+), JRNZ, L1 BWR ( branch )
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( don't branch )
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IX DECd, IX DECd, IX DECd, IX DECd,
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IY INCd,
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BC INCd,
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;CODE
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blk/305
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blk/305
@ -5,8 +5,7 @@ CODE EXECUTE
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CODE EXIT
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PC ORG @ 0x0d + ! ( stable ABI JP )
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L 0 IX+ LDrIXY,
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H 1 IX+ LDrIXY,
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C 0 IX+ LDrIXY,
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B 1 IX+ LDrIXY,
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IX DECd, IX DECd,
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HL PUSH, IY POP, ( --> IP )
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JPNEXT,
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blk/306
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blk/306
@ -3,8 +3,7 @@ PC ORG @ 0x25 + ! ( stable ABI JP )
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( Literal value to push to stack is next to (n) reference
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in the atom list. That is where IP is currently pointing.
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Read, push, then advance IP. )
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E 0 IY+ LDrIXY,
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D 1 IY+ LDrIXY,
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IY INCd, IY INCd,
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DE PUSH,
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LDA(BC), L A LDrr, BC INCd,
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LDA(BC), H A LDrr, BC INCd,
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HL PUSH,
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;CODE
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blk/307
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blk/307
@ -3,9 +3,9 @@ PC ORG @ 0x2d + ! ( stable ABI JP )
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( Like (n) but instead of being followed by a 2 bytes
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number, it's followed by a string. When called, puts the
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string's address on PS )
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IY PUSH, HL POP, ( <-- IP )
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E (HL) LDrr, D 0 LDri,
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DE INCd,
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DE ADDIYd,
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HL PUSH,
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BC PUSH,
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LDA(BC), C ADDr,
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IFC, B INCr, THEN,
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C A LDrr,
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BC INCd,
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;CODE
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blk/308
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blk/308
@ -1,6 +1,6 @@
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CODE ROT ( a b c -- b c a )
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HL POP, ( C ) DE POP, ( B ) BC POP, ( A ) chkPS,
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DE PUSH, ( B ) HL PUSH, ( C ) BC PUSH, ( A )
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HL POP, ( C ) DE POP, ( B ) IY POP, ( A ) chkPS,
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DE PUSH, ( B ) HL PUSH, ( C ) IY PUSH, ( A )
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;CODE
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CODE DUP ( a -- a a )
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HL POP, chkPS,
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blk/328
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blk/328
@ -1,4 +1,4 @@
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CODE S=
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CODE S= EXX, ( protect BC )
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DE POP, HL POP, chkPS,
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LDA(DE),
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(HL) CPr,
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@ -12,4 +12,4 @@ CODE S=
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DJNZ, AGAIN,
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THEN,
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PUSHZ,
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;CODE
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EXX, ( unprotect BC ) ;CODE
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4
blk/603
4
blk/603
@ -1,5 +1,5 @@
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( Computes n into crc c with polynomial 0x1021 )
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CODE _crc16 ( c n -- c )
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CODE _crc16 ( c n -- c ) EXX, ( protect BC )
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HL POP, ( n ) DE POP, ( c )
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A L LDrr, D XORr, D A LDrr,
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B 8 LDri,
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@ -11,4 +11,4 @@ CODE _crc16 ( c n -- c )
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THEN,
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DJNZ, AGAIN,
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DE PUSH,
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;CODE
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EXX, ( unprotect BC ) ;CODE
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