src/cpu.c: alot of refactoring, store state in a struct. and make vm.c "own" the state.

src/cpu.c

@@ -31,9 +31,6 @@
 #include "syscall.h"
 #include "instr.h"
 
-// Registers r0, r15
-int16_t reg[CPU_NUM_REGS] = { 0 };
-
 /* Program */
 unsigned char *instr_mem = NULL;
 unsigned long instr_cnt = 0;
@@ -47,7 +44,7 @@ unsigned char cpu_flags = CPU_FLAGS_HALT;
 
 #define debug(...) fprintf(stderr, __VA_ARGS__)
 
-static void execute(struct instr *instr) {
+static void execute(struct cpu_state *state, struct instr *instr) {
 
 	switch(instr->opcode) {
 	case OP_NOOP :
@@ -56,128 +53,112 @@ static void execute(struct instr *instr) {
 		break;
 	case OP_ADD :
 		debug("add\tr%i r%i r%i\n", instr->r.rs, instr->r.r0, instr->r.r1);
-		reg[instr->r.rs] = reg[instr->r.r0] + reg[instr->r.r1];
+		state->reg[instr->r.rs] = state->reg[instr->r.r0] + state->reg[instr->r.r1];
 		break;
 	case OP_MOVL :
 		debug("movl\tr%i #%i\n", instr->i.rs, instr->i.imm);
-		reg[instr->r.rs] = (reg[instr->r.rs] & 0xFF00) | instr->i.imm;
+		state->reg[instr->r.rs] = (state->reg[instr->r.rs] & 0xFF00) | instr->i.imm;
 		break;
 	case OP_MOVH :
 		debug("movh\tr%i #%i\n", instr->i.rs, instr->i.imm);
-		reg[instr->r.rs] = (reg[instr->r.rs] & 0x00FF) | (((uint16_t) instr->i.imm) << 8);
+		state->reg[instr->r.rs] = (state->reg[instr->r.rs] & 0x00FF) | (((uint16_t) instr->i.imm) << 8);
 		break;
 	case OP_LW :
 		debug("lw\tr%i r%i #%i\n", instr->r.rs, instr->r.r0, instr->r.r1);
-		reg[instr->r.rs] = mm_lw(reg[instr->r.r0] + instr->r.r1);
+		state->reg[instr->r.rs] = mm_lw(state->reg[instr->r.r0] + instr->r.r1);
 		break;
 	case OP_SW :
 		debug("sw\tr%i r%i #%i\n", instr->r.rs, instr->r.r0, instr->r.r1);
-		mm_sw(reg[instr->r.rs] + instr->r.r1, reg[instr->r.r0]);
+		mm_sw(state->reg[instr->r.rs] + instr->r.r1, state->reg[instr->r.r0]);
 		break;
 	case OP_JMP :
 		debug("jmp\t#%i\n", instr->j.addr);
-		cpu_set_pc(instr->j.addr);
+		cpu_set_pc(state, instr->j.addr);
 		break;
 	case OP_JR :
 		debug("jr\tr%i(#%i)\n", instr->i.rs, instr->i.imm);
-		cpu_set_pc(reg[instr->r.rs] + instr->i.imm);
+		cpu_set_pc(state, state->reg[instr->r.rs] + instr->i.imm);
 		break;
 	case OP_BEQ :
 		debug("beq\tr%i r%i #%i\n", instr->ri.rs, instr->ri.r0, instr->ri.offset);
 		// Compare rs, r0
-		if (reg[instr->ri.rs] == reg[instr->ri.r0])
+		if (state->reg[instr->ri.rs] == state->reg[instr->ri.r0])
-			cpu_set_pc(pc + instr->ri.offset);
+			cpu_set_pc(state, state->pc + instr->ri.offset);
 		break;
 	case OP_INT :
 		debug("int %i(#%i)\n", instr->r.rs, instr->i.imm);
-		vm_syscall(instr->i.rs, instr->i.imm, reg);
+		vm_syscall(instr->i.rs, instr->i.imm, state->reg);
 		break;
 	default :
 		fprintf(stderr, "Invalid instruction (%.2X)\n", instr->opcode);
-		cpu_flags |= CPU_FLAGS_HALT;
+		state->flags |= CPU_FLAGS_HALT;
 		break;
 	}
 }
 
-void print_memory() {
+void cpu_init(struct cpu_state *state)
+{
+	state->pc = 0;
+	state->flags = 0;
+	memset(state->reg, 0, sizeof(state->reg[0]) * CPU_NUM_REGS);
 
-	int i = 0;
+	state->instr_mem = NULL;
-
+	state->instr_cnt = 0;
-	printf("\n");
-
-	for(i = 0; i < 32; i++) {
-		printf("%.2X ", memory[i]);
-	}
-	printf("\n");
 }
 
-void print_reg() {
+int cpu_instr_load(struct cpu_state *state, void *ptr, unsigned len) {
-
-	int i = 0;
-
-	printf("\n");
-
-	for(i = 0; i < 16; i++) {
-		printf("r%i = %i\n", i, reg[i]);
-	}
-	printf("\n");
-}
-
-static unsigned char* instr_fetch() {
-
-	if (pc + 1 >= instr_cnt >> 1)
-		cpu_flags |= CPU_FLAGS_HALT;
-
-	return instr_mem + (pc++ << 1);
-}
-
-int cpu_instr_load(void *ptr, unsigned len) {
 
 	if (len % 2) {
 		fprintf(stderr, "Error: Instruction length must be a multiple of 2\n");
 		return -1;
 	}
 
-	instr_mem = ptr;
+	state->instr_mem = ptr;
-	instr_cnt = len;
+	state->instr_cnt = len;
 	return len;
 }
 
-void cpu_instr_unload() {
+void cpu_instr_unload(struct cpu_state *state) {
 
-	instr_mem = NULL;
+	state->instr_mem = NULL;
-	instr_cnt = 0;
+	state->instr_cnt = 0;
 }
 
-void cpu_set_pc(uint16_t addr) {
+void cpu_set_pc(struct cpu_state *state, uint16_t addr) {
 
 	if (addr > instr_cnt / 2) {
 		fprintf(stderr, "Runtime error: Invalid instruction address %ui\n", addr);
-		cpu_flags |= CPU_FLAGS_HALT;
+		state->flags |= CPU_FLAGS_HALT;
 		return;
 	}
-	pc = addr;
+	state->pc = addr;
 }
 
-void cpu_run() {
+static unsigned char* instr_fetch(struct cpu_state *state) {
 
-	mm_init();
+	if (state->pc + 1 >= state->instr_cnt >> 1)
+		state->flags |= CPU_FLAGS_HALT;
 
-	cpu_flags &= ~CPU_FLAGS_HALT;
+	return state->instr_mem + (state->pc++ << 1);
+}
 
-	while(!(cpu_flags & CPU_FLAGS_HALT)) {
+int cpu_tick(struct cpu_state *state) {
-		struct instr instr;
-		unsigned char* next = instr_fetch();
 
-		// decode instruction.
+	struct instr instr;
-		instr_decode(next, &instr);
+	unsigned char* next;
 
-		// Execute it.
+	if (state->flags & CPU_FLAGS_HALT) {
-		execute(&instr);
+		return 1;
 	}
 
-	print_reg();
+	// Fetch next instruction
-	print_memory();
+	next = instr_fetch(state);
 
-	mm_exit();
+	// decode instruction.
+	instr_decode(next, &instr);
+
+	// Execute it.
+	execute(state, &instr);
+
+	return 0;
 }

src/cpu.h

@@ -25,12 +25,31 @@
 
 #define CPU_NUM_REGS 16
 
-int cpu_instr_load(void *ptr, unsigned len);
+#define CPU_FLAGS_HALT (1<<0)
 
-void cpu_instr_unload();
+struct cpu_state {
+	// Registers r0, r15
+	int16_t reg[CPU_NUM_REGS];
 
-void cpu_set_pc(uint16_t addr);
+	// Program counter
+	uint16_t pc;
 
-void cpu_run();
+	// flags
+	unsigned char flags;
+
+	// Instruction
+	unsigned char *instr_mem;
+	unsigned long instr_cnt;
+};
+
+void cpu_init(struct cpu_state *state);
+
+int cpu_instr_load(struct cpu_state *state, void *ptr, unsigned len);
+
+void cpu_instr_unload(struct cpu_state *state);
+
+void cpu_set_pc(struct cpu_state *state, uint16_t addr);
+
+int cpu_tick(struct cpu_state *state);
 
 #endif /* CPU_H */

src/vm.c

@@ -25,8 +25,11 @@
 #include <fcntl.h>
 #include <errno.h>
 #include <unistd.h>
+#include "mm.h"
 #include "cpu.h"
 
+struct cpu_state state;
+
 // Load program from file
 unsigned long load_program(int fd, unsigned char **buf) {
 
@@ -46,8 +49,53 @@ unsigned long load_program(int fd, unsigned char **buf) {
 	return rc;
 }
 
+void print_memory() {
+
+	int i = 0;
+
+	printf("\n");
+
+	for(i = 0; i < 32; i++) {
+		printf("%.2X ", memory[i]);
+	}
+	printf("\n");
+}
+
+void print_regs(uint16_t *regs) {
+
+	int i = 0;
+
+	printf("\n");
+
+	for(i = 0; i < CPU_NUM_REGS; i++) {
+		printf("r%i = %i\n", i, regs[i]);
+	}
+	printf("\n");
+}
+
+void run(unsigned char *instr_ptr, unsigned instr_len) {
+
+	int rc;
+
+	mm_init();
+	cpu_init(&state);
+
+	cpu_instr_load(&state, instr_ptr, instr_len);
+
+	do {
+		rc = cpu_tick(&state);
+	} while(rc == 0);
+
+	print_regs(state.reg);
+
+	print_memory();
+
+	mm_exit();
+}
+
 int main(int argc, char **argv) {
 
+	int rc;
 	int fd;
 	unsigned char *instr_ptr;
 	unsigned instr_len;
@@ -70,9 +118,8 @@ int main(int argc, char **argv) {
 	if (instr_len < 0)
 		return 1;
 
-	cpu_instr_load(instr_ptr, instr_len);
+	// Execute the program.
-
+	run(instr_ptr, instr_len);
-	cpu_run();
 
 	if (instr_ptr)
 		free(instr_ptr);