From 4f99b1e1a4528d679b64915446663091ca09bb7a Mon Sep 17 00:00:00 2001
From: Mustafa Quraish <mustafaq9@gmail.com>
Date: Sat, 5 Feb 2022 20:28:56 -0500
Subject: [compiler.cup] Add support for function calls!

---
 compiler/codegen.cup | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

(limited to 'compiler/codegen.cup')

diff --git a/compiler/codegen.cup b/compiler/codegen.cup
index 407fab5..975844d 100644
--- a/compiler/codegen.cup
+++ b/compiler/codegen.cup
@@ -27,6 +27,11 @@ fn emit_asm(msg: char*) {
 }
 
 fn emit_num(num: int) {
+    // FIXME: Just support printing negatives directly.
+    if (num < 0) {
+        emit_asm("-");
+        num = -num;
+    }
     fputu(gen_out_file, num);
 }
 
@@ -35,6 +40,8 @@ fn generate_syscall(num: int) {
     emit_asm("    syscall\n");
 }
 
+fn generate_expr_into_rax(node: Node*);
+
 fn generate_lvalue_into_rax(node: Node*) {
     if (node.typ == AST_LOCAL_VAR) {
         let offset = node.d.variable.offset;
@@ -45,6 +52,20 @@ fn generate_lvalue_into_rax(node: Node*) {
     }
 }
 
+fn generate_function_call(node: Node*) {
+    let total_size = 0;
+    let n = node.d.call.args.size;
+    for (let i = n-1; i >= 0; --i) {
+        let expr: Node* = node.d.call.args.data[i];
+        generate_expr_into_rax(expr);
+        emit_asm("    push rax\n");
+        // TODO: this might be an issue if we pass structs some day
+        total_size = total_size + 8;
+    }
+    emit_asm3("    call func_", node.d.call.func.d.func.name, "\n");
+    emit_asm("    add rsp, "); emit_num(total_size); emit_asm("\n");
+}
+
 fn generate_expr_into_rax(node: Node*) {
     if (node.typ == AST_LITERAL) {
         if (node.etyp.typ == TYPE_INT) {
@@ -233,6 +254,9 @@ fn generate_expr_into_rax(node: Node*) {
         emit_asm("    pop rbx\n");
         emit_asm("    mov [rbx], rax\n");
 
+    } else if (node.typ == AST_FUNCCALL) {
+        generate_function_call(node);
+
     } else {
         die2("Unsupported node type in generate_expr_into_rax: ", node_type_to_string(node.typ));
     }
-- 
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