Merge pull request #10 from peterferrie/main

shave some bytes
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Justine Tunney 2021-11-06 00:59:27 -07:00 committed by GitHub
commit 9f108b0d60
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2 changed files with 97 additions and 101 deletions

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@ -30,8 +30,9 @@
.set ATOM_CONS, 61
.set ATOM_EQ, 71
.set g_token, 0x4000
.set g_str, 0x4080
.set g_token, 0x7800
.set g_str, 0x0
.set g_mem, 0x3600
.set boot, 0x7c00
////////////////////////////////////////////////////////////////////////////////
@ -51,19 +52,19 @@ _begin: push %cs # memory model cs=ds=es = 0x600
push %cs
pop %ds
pop %es
pop %ss
mov $0x7c00-0x600,%cx
mov %cx,%sp
cld
xor %ax,%ax
mov %ax,%fs # fs = &g_mem
xor %di,%di
rep stosb # clears our bss memory
main: mov $g_str,%di
mov $kSymbols,%si
push %si
xor %di,%di # mov g_str, %di
mov $37,%cx
cld
rep movsb
0: mov $'\n',%dl
pop %cx
pop %ss
mov %cx,%sp
mov $g_mem,%ax
mov %ax,%fs # fs = &g_mem
rep stosb # clears our bss memory
main: mov $'\n',%dl
call GetToken
call GetObject
mov $NIL,%dx
@ -71,10 +72,11 @@ main: mov $g_str,%di
call PrintObject
mov $'\r',%al
call PutChar
jmp 0b
jmp main
GetToken: # GetToken():al, dl is g_look
mov $g_token,%di
mov %di,%si
1: mov %dl,%al
cmp $' ',%al
jbe 2f
@ -92,35 +94,6 @@ GetToken: # GetToken():al, dl is g_look
xchg %cx,%ax
ret
GetObject: # called just after GetToken
cmpb $'(',%al
je GetList
mov $g_token,%si
.Intern:
mov $g_str,%di
xor %al,%al
0: mov $-1,%cl
push %di # save 1
1: cmpsb
jne 2f
cmp -1(%di),%al
jne 1b
jmp 4f
2: pop %si # drop 1
mov $g_token,%si
repne scasb
cmp (%di),%al
jne 0b
push %di # StpCpy
3: lodsb
stosb
test %al,%al
jnz 3b
4: pop %ax # restore 1
add $-g_str,%ax # stc
adc %ax,%ax # ax = 2 * ax + carry
.ret: ret
.PutObject: # .PutObject(c:al,x:di)
call PutChar # preserves di
xchg %di,%ax
@ -132,7 +105,7 @@ PrintObject: # PrintObject(x:ax)
jz .PrintList
.PrintAtom:
shr %di
lea g_str(%di),%si
mov %di,%si # lea g_str(%di),%si
.PrintString: # nul-terminated in si
lodsb
test %al,%al
@ -156,6 +129,36 @@ PrintObject: # PrintObject(x:ax)
4: mov $')',%al
jmp PutChar
GetObject: # called just after GetToken
cmpb $'(',%al
je GetList
.Intern:
xor %di,%di # mov $g_str,%di
xor %al,%al
0: push %di # save 1
1: cmpsb
jne 2f
dec %di
scasb
jne 1b
jmp 5f
2: pop %si # drop 1
mov $g_token,%si
3: scasb
jne 3b
cmp (%di),%al
jne 0b
push %di # StpCpy
4: movsb
dec %di
scasb
jnz 4b
5: pop %ax # restore 1
# add $-g_str,%ax
add %ax,%ax # ax = 2 * ax
inc %ax # + 1
.ret: ret
GetChar:
xor %ax,%ax # get keystroke
int $0x16 # keyboard service
@ -164,7 +167,7 @@ GetChar:
PutChar:
# push %bx # don't clobber di,si,cx,dx
# push %bp # original ibm pc scroll up bug
mov $7,%bx # normal mda/cga style page zero
xor %bx,%bx # normal mda/cga style page zero
mov $0x0e,%ah # teletype output al cp437
int $0x10 # vidya service
# pop %bp # preserves al
@ -174,16 +177,26 @@ PutChar:
mov $'\n',%al
jmp PutChar # bx volatile, bp never used
GetList:call GetToken
cmpb $')',%al
je .retF
call GetObject
push %ax # save 1
call GetList
jmp xCons
////////////////////////////////////////////////////////////////////////////////
Pairlis:cmp $NIL,%di # Pairlis(x:di,y:si,a:dx):ax
je 1f
push 2(%di) # save 1 Cdr(x)
lodsw
push (%si) # save 2 Cdr(y)
mov (%di),%di
xchg %ax,%si
call Cons # preserves dx
pop %si # restore 2
pop %di # restore 1
push %ax # save 3
call Pairlis
xchg %ax,%si
pop %di # restore 3
jmp Cons # can be inlined here
1: xchg %dx,%ax
ret
Evlis: cmp $NIL,%di # Evlis(m:di,a:dx):ax
je 1f
push 2(%di) # save 1 Cdr(m)
@ -200,33 +213,24 @@ xCons: xchg %ax,%si
# jmp Cons
Cons: xchg %di,%ax
mov %fs,%di
push %di
stosw
xchg %si,%ax
stosw
mov %di,%fs
pop %ax
ret
xchg %di,%ax
mov %fs,%di
mov %ax,%fs
1: xchg %di,%ax
ret
Pairlis:cmp $NIL,%di # Pairlis(x:di,y:si,a:dx):ax
je 1f
push 2(%di) # save 1 Cdr(x)
push 2(%si) # save 2 Cdr(y)
mov (%di),%di
mov (%si),%si
call Cons # preserves dx
pop %si # restore 2
pop %di # restore 1
push %ax # save 3
call Pairlis
xchg %ax,%si
pop %di # restore 3
jmp Cons # can be inlined here
1: xchg %dx,%ax
ret
GetList:call GetToken
cmpb $')',%al
je .retF
call GetObject
push %ax # save 1
call GetList
jmp xCons
1: mov 2(%di),%di # di = Cdr(c)
Evcon: push %di # save c
mov (%di),%di # di = Car(c)
mov (%di),%ax # ax = Caar(c)
@ -235,10 +239,8 @@ Evcon: push %di # save c
pop %dx # restore a
pop %di # restore c
cmp $NIL,%ax
jne 2f
mov 2(%di),%di # di = Cdr(c)
jmp Evcon
2: mov (%di),%di # di = Car(c)
jz 1b
mov (%di),%di # di = Car(c)
.EvCadr:call Cadr # ax = Cadar(c)
# jmp Eval
@ -247,8 +249,8 @@ Eval: test $1,%al # Eval(e:ax,a:dx):ax
xchg %ax,%di # di = e
mov (%di),%ax # ax = Car(e)
cmp $ATOM_QUOTE,%ax # maybe CONS
je Cadr
mov 2(%di),%di # di = Cdr(e)
je .retA
cmp $ATOM_COND,%ax
je Evcon
.Ldflt2:push %ax # save 2
@ -267,23 +269,6 @@ Apply: test $1,%al # Apply(fn:ax,x:si:a:dx):ax
xchg %ax,%dx
pop %di # restore 1
jmp .EvCadr
.switch:cmp $ATOM_EQ,%ax
ja .dflt1
mov (%si),%di # di = Car(x)
.ifCar: cmp $ATOM_CAR,%al
jne .ifCdr
mov (%di),%ax
ret
.ifCdr: cmp $ATOM_CDR,%al
jne .ifAtom
mov 2(%di),%ax
ret
.ifAtom:cmp $ATOM_ATOM,%al
jne .ifCons
test $1,%di
jnz .retT
.retF: mov $NIL,%ax # ax = NIL
ret
.ifCons:mov 2(%si),%si # si = Cdr(x)
mov (%si),%si # si = Cadr(x)
cmp $ATOM_CONS,%al
@ -292,6 +277,20 @@ Apply: test $1,%al # Apply(fn:ax,x:si:a:dx):ax
jne .retF
.retT: mov $ATOM_T,%al # ax = ATOM_T
ret
.switch:cmp $ATOM_EQ,%ax
ja .dflt1
mov (%si),%di # di = Car(x)
.ifCar: cmp $ATOM_CAR,%al
je .retA
.ifCdr: cmp $ATOM_CDR,%al
cmove 2(%di),%ax
je .retD
.ifAtom:cmp $ATOM_ATOM,%al
jne .ifCons
test $1,%di
jnz .retT
.retF: mov $NIL,%ax # ax = NIL
.retD: ret
.dflt1: push %si # save x
push %dx # save a
call Eval
@ -300,19 +299,16 @@ Apply: test $1,%al # Apply(fn:ax,x:si:a:dx):ax
jmp Apply
Cadr: mov 2(%di),%di # contents of decrement register
mov (%di),%ax # contents of address register
.retA: mov (%di),%ax # contents of address register
ret
assoc1: mov 2(%si),%dx # dx = Cdr(y)
# jmp Assoc
1: mov 2(%si),%dx # dx = Cdr(y)
Assoc: cmp $NIL,%dx # Assoc(x:ax,y:dx):ax
mov %dx,%si
je .retF
mov (%si),%bx # bx = Car(y)
mov (%bx),%cx # cx = Caar(y)
cmp %cx,%ax
jne assoc1
cmp %ax,(%bx) # (%bx) = Caar(y)
jne 1b
mov 2(%bx),%ax # ax = Cdar(y)
ret