Support function definition up to 6 parameters

chibi.h

@@ -48,11 +48,16 @@ extern Token *token;
 // Local variable
 typedef struct Var Var;
 struct Var {
-  Var *next;
   char *name; // Variable name
   int offset; // Offset from RBP
 };
 
+typedef struct VarList VarList;
+struct VarList {
+  VarList *next;
+  Var *var;
+};
+
 // AST node
 typedef enum {
   ND_ADD,       // +
@@ -106,8 +111,10 @@ typedef struct Function Function;
 struct Function {
   Function *next;
   char *name;
+  VarList *params;
+
   Node *node;
-  Var *locals;
+  VarList *locals;
   int stack_size;
 };
 

codegen.c

@@ -198,6 +198,13 @@ void codegen(Function *prog) {
     printf("  mov rbp, rsp\n");
     printf("  sub rsp, %d\n", fn->stack_size);
 
+    // Push arguments to the stack
+    int i = 0;
+    for (VarList *vl = fn->params; vl; vl = vl->next) {
+      Var *var = vl->var;
+      printf("  mov [rbp-%d], %s\n", var->offset, argreg[i++]);
+    }
+
     // Emit code
     for (Node *node = fn->node; node; node = node->next)
       gen(node);

main.c

@@ -12,9 +12,9 @@ int main(int argc, char **argv) {
   // Assign offsets to local variables.
   for (Function *fn = prog; fn; fn = fn->next) {
     int offset = 0;
-    for (Var *var = prog->locals; var; var = var->next) {
+    for (VarList *vl = fn->locals; vl; vl = vl->next) {
       offset += 8;
-      var->offset = offset;
+      vl->var->offset = offset;
     }
     fn->stack_size = offset;
   }

parse.c

@@ -2,13 +2,15 @@
 
 // All local variable instances created during parsing are
 // accumulated to this list.
-Var *locals;
+static VarList *locals;
 
 // Find a local variable by name.
 static Var *find_var(Token *tok) {
-  for (Var *var = locals; var; var = var->next)
+  for (VarList *vl = locals; vl; vl = vl->next) {
+    Var *var = vl->var;
     if (strlen(var->name) == tok->len && !strncmp(tok->str, var->name, tok->len))
       return var;
+  }
   return NULL;
 }
 
@@ -45,9 +47,12 @@ static Node *new_var_node(Var *var) {
 
 static Var *new_lvar(char *name) {
   Var *var = calloc(1, sizeof(Var));
-  var->next = locals;
   var->name = name;
-  locals = var;
+
+  VarList *vl = calloc(1, sizeof(VarList));
+  vl->var = var;
+  vl->next = locals;
+  locals = vl;
   return var;
 }
 
@@ -74,25 +79,42 @@ Function *program(void) {
   return head.next;
 }
 
-// function = ident "(" ")" "{" stmt* "}"
+static VarList *read_func_params(void) {
+  if (consume(")"))
+    return NULL;
+
+  VarList *head = calloc(1, sizeof(VarList));
+  head->var = new_lvar(expect_ident());
+  VarList *cur = head;
+
+  while (!consume(")")) {
+    expect(",");
+    cur->next = calloc(1, sizeof(VarList));
+    cur->next->var = new_lvar(expect_ident());
+    cur = cur->next;
+  }
+
+  return head;
+}
+
+// function = ident "(" params? ")" "{" stmt* "}"
+// params   = ident ("," ident)*
 static Function *function(void) {
   locals = NULL;
 
-  char *name = expect_ident();
+  Function *fn = calloc(1, sizeof(Function));
+  fn->name = expect_ident();
   expect("(");
-  expect(")");
+  fn->params = read_func_params();
   expect("{");
 
   Node head = {};
   Node *cur = &head;
-
   while (!consume("}")) {
     cur->next = stmt();
     cur = cur->next;
   }
 
-  Function *fn = calloc(1, sizeof( Function));
-  fn->name = name;
   fn->node = head.next;
   fn->locals = locals;
   return fn;

test.sh

@@ -87,5 +87,8 @@ assert 2 'main() { return sub(5, 3); }'
 assert 21 'main() { return add6(1,2,3,4,5,6); }'
 
 assert 32 'main() { return ret32(); } ret32() { return 32; }'
+assert 7 'main() { return add2(3,4); } add2(x,y) { return x+y; }'
+assert 1 'main() { return sub2(4,3); } sub2(x,y) { return x-y; }'
+assert 55 'main() { return fib(9); } fib(x) { if (x<=1) return 1; return fib(x-1) + fib(x-2); }'
 
 echo OK