Added return stack

README.md

@@ -10,6 +10,10 @@ cc uxn.c -std=c89 -Os -DNDEBUG -g0 -s -Wall -Wno-unknown-pragmas -o uxn
 
 ## Assembly Syntax
 
+- `:label`, a named offset
+- `+literal`, a numeric value
+- `.pointer`, pointer to a label
+
 ```
 < comment >
 
@@ -30,31 +34,16 @@ $01 < pointer8 >
 :label ADD RTS
 ```
 
-## Design
-
-### CPU
-
-- Build stack with pointer
-- Print stack
-- Build memory
-
-### PPU
-
-### Assembly
-
-#### Addressing 
-
-- `label`, a named offset[TODO]
-- `literal`, a numeric value
-- `pointer`, pointer to an address[TODO]
-
-### Assembler
-
-
-### Emulator
-
-- SDL Layer
+## TODOs
 
+- Implement addressing
+- Implement 16 bits operations
+- Jumps should be relative
+- Catch overflow/underflow
+- Implement literals like `[2]`, and `[ 2 3 ]`.
+- Audo-detect literals length.
+- SDL Layer Emulator
+- Build PPU
 
 ## Refs
 

example.usm

@@ -1,5 +1,18 @@
 < comment >
 
-[3 1 2 3 ] pop dup swp ovr rot 
+.deep JSR [4 6 7 8 9 ] BRK
+
+:deep
+	[2 1 2 ] 
+	.deeper JSR 
+	RTS
+
+:deeper
+	[3 3 4 5 ] 
+	.deeperyet JSR
+	RTS
+
+:deeperyet
+	[2 aa bb ]
+	RTS
 	
-brk

uxn.c

@@ -24,8 +24,9 @@ typedef struct {
 	Uint8 literal;
 	Uint8 status, counter;
 	Uint8 memory[STACK_DEPTH];
-	Uint8 mptr, sptr;
+	Uint8 mptr, sptr, rsptr;
 	Uint8 stack[STACK_DEPTH];
+	Uint8 rstack[STACK_DEPTH];
 	Uint8 address[STACK_DEPTH];
 } Computer;
 
@@ -61,20 +62,66 @@ echo(Uint8 *s, Uint8 len, char *name)
 	printf("\n\n");
 }
 
-#pragma mark - Operations
-
 void
-op_push(Uint8 *s, Uint8 *ptr, Uint8 v)
+spush(Uint8 v)
 {
-	s[(*ptr)++] = v;
+	cpu.stack[cpu.sptr++] = v;
 }
 
 Uint8
-op_pop(Uint8 *s, Uint8 *ptr)
+spop(void)
 {
-	return s[--*ptr];
+	return cpu.stack[--cpu.sptr];
 }
 
+void
+rspush(Uint8 v)
+{
+	cpu.rstack[cpu.rsptr++] = v;
+}
+
+Uint8
+rspop(void)
+{
+	return cpu.rstack[--cpu.rsptr];
+}
+
+#pragma mark - Operations
+
+/* clang-format off */
+
+void op_brk() { setflag(FLAG_HALT, 1); }
+void op_lit() { cpu.literal += cpu.memory[cpu.mptr++]; }
+void op_nop() { }
+void op_drp() { spop(); }
+void op_dup() { spush(cpu.stack[cpu.sptr - 1]); }
+void op_swp() { Uint8 b = spop(), a = spop(); spush(b); spush(a); }
+void op_ovr() { spush(cpu.stack[cpu.sptr - 2]); }
+void op_rot() { Uint8 c = spop(),b = spop(),a = spop(); spush(b); spush(c); spush(a); }
+void op_jmp() { cpu.mptr = spop(); }
+void op_jsr() { rspush(cpu.mptr); cpu.mptr = spop(); }
+void op_jeq() { if(getflag(FLAG_ZERO)) cpu.mptr = spop(); }
+void op_rts() {	cpu.mptr = rspop(); }
+void op_equ() { setflag(FLAG_ZERO, spop() == spop()); }
+void op_neq() { setflag(FLAG_ZERO, spop() != spop()); }
+void op_lth() {	setflag(FLAG_ZERO, spop() < spop()); }
+void op_gth() {	setflag(FLAG_ZERO, spop() > spop()); }
+void op_and() {	spush(spop() & spop()); }
+void op_ora() {	spush(spop() | spop()); }
+void op_rol() { spush(spop() << 1); }
+void op_ror() { spush(spop() >> 1); }
+void op_add() { spush(spop() + spop()); }
+void op_sub() { spush(spop() - spop()); }
+void op_mul() { spush(spop() * spop()); }
+void op_div() { spush(spop() / spop()); }
+
+void (*ops[])(void) = {
+	op_brk, op_lit, op_nop, op_drp, op_dup, op_swp, op_ovr, op_rot, 
+	op_jmp, op_jsr, op_jeq, op_rts, op_equ, op_neq, op_gth, op_lth, 
+	op_and, op_ora, op_rol, op_ror, op_add, op_sub, op_mul, op_div};
+
+/* clang-format on */
+
 void
 reset(void)
 {
@@ -105,42 +152,13 @@ void
 eval()
 {
 	Uint8 instr = cpu.memory[cpu.mptr++];
-	Uint8 a, b, c;
 	if(cpu.literal > 0) {
-		printf("push: %02x[%d](%d)\n", instr, cpu.literal, cpu.sptr);
-		op_push(cpu.stack, &cpu.sptr, instr);
+		spush(instr);
 		cpu.literal--;
 		return;
 	}
-	switch(instr) {
-	case 0x0: setflag(FLAG_HALT, 1); break;
-	case 0x1: cpu.literal += cpu.memory[cpu.mptr++]; break;
-	case 0x2: printf("??\n"); break;
-	case 0x3: /* pop */
-		op_pop(cpu.stack, &cpu.sptr);
-		break;
-	case 0x4: /* dup */
-		op_push(cpu.stack, &cpu.sptr, cpu.stack[cpu.sptr - 1]);
-		break;
-	case 0x5: /* swp */
-		b = op_pop(cpu.stack, &cpu.sptr);
-		a = op_pop(cpu.stack, &cpu.sptr);
-		op_push(cpu.stack, &cpu.sptr, b);
-		op_push(cpu.stack, &cpu.sptr, a);
-		break;
-	case 0x6: /* ovr */
-		op_push(cpu.stack, &cpu.sptr, cpu.stack[cpu.sptr - 2]);
-		break;
-	case 0x7: /* rot */
-		c = op_pop(cpu.stack, &cpu.sptr);
-		b = op_pop(cpu.stack, &cpu.sptr);
-		a = op_pop(cpu.stack, &cpu.sptr);
-		op_push(cpu.stack, &cpu.sptr, b);
-		op_push(cpu.stack, &cpu.sptr, c);
-		op_push(cpu.stack, &cpu.sptr, a);
-		break;
-	default: printf("Unknown instruction: #%02x\n", instr);
-	}
+	if(instr < 24)
+		(*ops[instr])();
 }
 
 void

uxnasm.c

@@ -12,6 +12,7 @@ WITH REGARD TO THIS SOFTWARE.
 */
 
 #define PRGLEN 256
+#define LABELIDLEN 32
 
 typedef unsigned char Uint8;
 
@@ -20,7 +21,13 @@ typedef struct {
 	Uint8 data[PRGLEN];
 } Program;
 
-char labels[256][16];
+typedef struct {
+	Uint8 addr;
+	char name[LABELIDLEN];
+} Label;
+
+int labelslen;
+Label labels[256];
 
 char opcodes[][4] = {
 	"BRK",
@@ -40,6 +47,14 @@ char opcodes[][4] = {
 	"NEQ",
 	"LTH",
 	"GTH",
+	"---",
+	"---",
+	"---",
+	"---",
+	"ADD",
+	"SUB",
+	"MUL",
+	"DIV"
 	/* */};
 
 Program p;
@@ -56,6 +71,16 @@ scmp(char *a, char *b) /* string compare */
 	return 0;
 }
 
+char *
+scpy(char *src, char *dst, int len) /* string copy */
+{
+	int i = 0;
+	while((dst[i] = src[i]) && i < len - 2)
+		i++;
+	dst[i + 1] = '\0';
+	return dst;
+}
+
 char *
 suca(char *s) /* string to uppercase */
 {
@@ -72,7 +97,7 @@ sihx(char *s)
 	int i = 0;
 	char c;
 	while((c = s[i++]))
-		if(!(c >= '0' && c <= '9') && !(c >= 'A' && c <= 'F'))
+		if(!(c >= '0' && c <= '9') && !(c >= 'a' && c <= 'f') && !(c >= 'A' && c <= 'F'))
 			return 0;
 	return 1;
 }
@@ -87,6 +112,8 @@ shex(char *s) /* string to num */
 			n = n * 16 + (c - '0');
 		else if(c >= 'A' && c <= 'F')
 			n = n * 16 + 10 + (c - 'A');
+		else if(c >= 'a' && c <= 'f')
+			n = n * 16 + 10 + (c - 'f');
 	return n;
 }
 
@@ -101,7 +128,10 @@ addprg(Uint8 hex)
 void
 addlabel(char *id, Uint8 addr)
 {
-	printf("new label: %s=%02x\n", id, addr);
+	Label *l = &labels[labelslen++];
+	scpy(suca(id), l->name, LABELIDLEN);
+	l->addr = addr;
+	printf("new label: %s=%02x\n", l->name, l->addr);
 }
 
 void
@@ -110,16 +140,39 @@ addconst(char *id, Uint8 value)
 	printf("new const: %s=%02x\n", id, value);
 }
 
+Label *
+findlabel(char *s)
+{
+	int i;
+	for(i = 0; i < labelslen; ++i)
+		if(scmp(labels[i].name, s))
+			return &labels[i];
+	return NULL;
+}
+
 Uint8
 findop(char *s)
 {
 	int i;
-	for(i = 0; i < 16; ++i)
+	for(i = 0; i < 24; ++i)
 		if(scmp(opcodes[i], s))
 			return i;
 	return 0;
 }
 
+int
+getlength(char *w)
+{
+	if(findop(w) || scmp(w, "BRK")) return 1;
+	if(w[0] == '.') return 3;
+	if(w[0] == ':') return 0;
+	if(w[0] == '[') return 2;
+	if(sihx(w)) return 1;
+	if(w[0] == ']') return 0;
+	printf("Unknown length %s\n", w);
+	return 0;
+}
+
 int
 comment(char *w, int *skip)
 {
@@ -136,10 +189,12 @@ void
 pass1(FILE *f)
 {
 	int skip = 0;
+	int addr = 0;
 	char word[64];
 	while(fscanf(f, "%s", word) == 1) {
-		if(comment(word, &skip))
-			continue;
+		if(comment(word, &skip)) continue;
+		if(word[0] == ':') addlabel(word + 1, addr);
+		addr += getlength(word);
 	}
 	rewind(f);
 }
@@ -151,6 +206,8 @@ pass2(FILE *f)
 	char word[64];
 	while(fscanf(f, "%s", word) == 1) {
 		Uint8 op;
+		Label *l;
+		if(word[0] == ':') continue;
 		suca(word);
 		if(comment(word, &skip)) continue;
 		if(word[0] == ']') continue;
@@ -167,7 +224,11 @@ pass2(FILE *f)
 			addprg(shex(word));
 		else if(scmp(word, "BRK"))
 			addprg(0x00);
-		else
+		else if((l = findlabel(word + 1))) {
+			addprg(0x01);
+			addprg(1);
+			addprg(l->addr);
+		} else
 			printf("unknown: %s\n", word);
 	}
 }