feat: support seven or more parameters/arguments

2 files changed, 54 insertions, 35 deletions

diff --git a/src/codegen.c b/src/codegen.c
index 97a9209..0b586be 100644
--- a/src/codegen.c
+++ b/src/codegen.c
@@ -56,7 +56,7 @@ static const char* param_reg(int n) {
 static void codegen_func_prologue(CodeGen* g, AstNode* ast) {
     fprintf(g->out, "  push rbp\n");
     fprintf(g->out, "  mov rbp, rsp\n");
-    for (int i = 0; i < ast->node_params->node_len; ++i) {
+    for (int i = 0; i < ast->node_params->node_len && i < 6; ++i) {
         fprintf(g->out, "  push %s\n", param_reg(i));
     }
     // Note: rsp must be aligned to 8.
@@ -363,6 +363,17 @@ static void codegen_assign_expr(CodeGen* g, AstNode* ast) {
     }
 }
 
+static void codegen_args(CodeGen* g, AstNode* args) {
+    // Evaluate arguments in the reverse order (right to left).
+    for (int i = args->node_len - 1; i >= 0; --i) {
+        AstNode* arg = &args->node_items[i];
+        codegen_expr(g, arg, GenMode_rval);
+    }
+    for (int i = 0; i < args->node_len && i < 6; ++i) {
+        fprintf(g->out, "  pop %s\n", param_reg(i));
+    }
+}
+
 static void codegen_func_call(CodeGen* g, AstNode* ast) {
     const char* func_name = ast->name;
 
@@ -395,41 +406,41 @@ static void codegen_func_call(CodeGen* g, AstNode* ast) {
     }
 
     AstNode* args = ast->node_args;
-    // Evaluate arguments in the reverse order (right to left).
-    for (int i = args->node_len - 1; i >= 0; --i) {
-        AstNode* arg = &args->node_items[i];
-        codegen_expr(g, arg, GenMode_rval);
-    }
-    for (int i = 0; i < args->node_len && i < 6; ++i) {
-        fprintf(g->out, "  pop %s\n", param_reg(i));
-    }
+    int overflow_args_count = args->node_len <= 6 ? 0 : args->node_len - 6;
 
     int label = codegen_new_label(g);
 
     fprintf(g->out, "  mov rax, rsp\n");
+    if (overflow_args_count % 2 == 1) {
+        fprintf(g->out, "  add rax, 8\n");
+    }
     fprintf(g->out, "  and rax, 15\n");
     fprintf(g->out, "  cmp rax, 0\n");
     fprintf(g->out, "  je .Laligned%d\n", label);
 
-    fprintf(g->out, "  mov rax, 0\n");
     fprintf(g->out, "  sub rsp, 8\n");
+    codegen_args(g, args);
+    fprintf(g->out, "  mov rax, 0\n");
     fprintf(g->out, "  call %s\n", func_name);
     fprintf(g->out, "  add rsp, 8\n");
-    fprintf(g->out, "  push rax\n");
 
     fprintf(g->out, "  jmp .Lend%d\n", label);
     fprintf(g->out, ".Laligned%d:\n", label);
 
+    codegen_args(g, args);
     fprintf(g->out, "  mov rax, 0\n");
     fprintf(g->out, "  call %s\n", func_name);
-    fprintf(g->out, "  push rax\n");
 
     fprintf(g->out, ".Lend%d:\n", label);
+    // Pop pass-by-stack arguments.
+    for (int i = 0; i < overflow_args_count; i++) {
+        fprintf(g->out, "  add rsp, 8\n");
+    }
+    fprintf(g->out, "  push rax\n");
 }
 
 static void codegen_lvar(CodeGen* g, AstNode* ast, GenMode gen_mode) {
-    fprintf(g->out, "  mov rax, rbp\n");
-    fprintf(g->out, "  sub rax, %d\n", ast->node_stack_offset);
+    fprintf(g->out, "  lea rax, %d[rbp]\n", -ast->node_stack_offset);
     fprintf(g->out, "  push rax\n");
     if (gen_mode == GenMode_rval) {
         codegen_lval2rval(g, ast->ty);
diff --git a/src/parse.c b/src/parse.c
index f336c0c..195a3b0 100644
--- a/src/parse.c
+++ b/src/parse.c
@@ -230,25 +230,33 @@ static int find_lvar(Parser* p, const char* name) {
 }
 
 static int calc_stack_offset(Parser* p, Type* ty, bool is_param) {
-    int align;
     if (is_param) {
         if (8 < type_sizeof(ty) || 8 < type_alignof(ty)) {
             fatal_error("too large");
         }
-        align = 8;
-    } else {
-        align = type_alignof(ty);
-    }
-
-    int offset;
-    if (p->lvars.len == 0) {
-        offset = 0;
+        int offset;
+        if (p->lvars.len == 0) {
+            offset = 0;
+        } else {
+            offset = p->lvars.data[p->lvars.len - 1].stack_offset;
+        }
+        if (offset < 0) {
+            return offset - 8;
+        } else if (offset >= 6 * 8) {
+            return -16;
+        } else {
+            return offset + 8;
+        }
     } else {
-        offset = p->lvars.data[p->lvars.len - 1].stack_offset;
+        int offset = 0;
+        for (size_t i = 0; i < p->lvars.len; i++) {
+            int o = p->lvars.data[i].stack_offset;
+            if (offset < o) {
+                offset = o;
+            }
+        }
+        return to_aligned(offset + type_sizeof(ty), type_alignof(ty));
     }
-
-    offset += type_sizeof(ty);
-    return to_aligned(offset, align);
 }
 
 static int add_lvar(Parser* p, const char* name, Type* ty, bool is_param) {
@@ -448,9 +456,6 @@ static AstNode* parse_arg_list(Parser* p) {
             break;
         }
     }
-    if (list->node_len > 6) {
-        fatal_error("too many arguments");
-    }
     return list;
 }
 
@@ -1008,9 +1013,6 @@ static AstNode* parse_parameter_type_list(Parser* p) {
         has_void |= params->node_items[i].ty->kind == TypeKind_void;
     }
 
-    if (params->node_len > 6) {
-        fatal_error("too many parameters");
-    }
     if (has_void) {
         if (params->node_len != 1) {
             fatal_error("invalid use of void param");
@@ -1464,8 +1466,14 @@ static AstNode* parse_func_def(Parser* p, AstNode* decls) {
     if (p->lvars.len == 0) {
         func->node_stack_size = 0;
     } else {
-        func->node_stack_size =
-            p->lvars.data[p->lvars.len - 1].stack_offset + type_sizeof(p->lvars.data[p->lvars.len - 1].ty);
+        int stack_size = 0;
+        for (size_t i = 0; i < p->lvars.len; i++) {
+            int s = p->lvars.data[i].stack_offset + type_sizeof(p->lvars.data[i].ty);
+            if (stack_size < s) {
+                stack_size = s;
+            }
+        }
+        func->node_stack_size = stack_size;
     }
     return func;
 }