initial commit

vm.c

@@ -0,0 +1,60 @@
+#include "vm.h"
+#include "gc.h"
+
+static I decode_sleb128(U8 **ptr) {
+  I result = 0;
+  I shift = 0;
+  U8 byte;
+
+  do {
+    byte = **ptr;
+    (*ptr)++;
+    result |= (I)(byte & 0x7F) << shift;
+    shift += 7;
+  } while (byte & 0x80);
+
+  if ((shift < 64) && (byte & 0x40)) {
+    result |= -(1LL << shift);
+  }
+
+  return result;
+}
+
+V vm_init(Vm *vm) {
+  vm->sp = vm->stack;
+  vm->rsp = vm->rstack;
+  gc_init(&vm->gc);
+
+  for (Z i = 0; i < STACK_SIZE; i++) {
+    vm->stack[i] = NIL;
+    gc_addroot(&vm->gc, &vm->stack[i]);
+  }
+}
+
+V vm_push(Vm *vm, O o) { *vm->sp++ = o; }
+O vm_pop(Vm *vm) { return *--vm->sp; }
+O vm_peek(Vm *vm) { return *(vm->sp - 1); }
+
+V vm_run(Vm *vm, Bc *chunk, I offset) {
+  I mark = gc_mark(&vm->gc);
+  for (Z i = 0; i < chunk->constants.count; i++)
+    gc_addroot(&vm->gc, &chunk->constants.items[i]);
+
+  vm->ip = chunk->items + offset;
+  for (;;) {
+    U8 opcode;
+    switch (opcode = *vm->ip++) {
+    case OP_NOP:
+      break;
+    case OP_RETURN:
+      return;
+    case OP_CONST: {
+      I idx = decode_sleb128(&vm->ip);
+      vm_push(vm, chunk->constants.items[idx]);
+      break;
+    }
+    }
+  }
+
+  gc_reset(&vm->gc, mark);
+}