1 files changed, 117 insertions, 17 deletions

diff --git a/src/builtins.c b/src/builtins.c
index 3922d54..2883c1d 100644
--- a/src/builtins.c
+++ b/src/builtins.c
@@ -1,19 +1,54 @@
 #include "builtins.h"
 #include "ast.h"
 #include "utils.h"
+#include "generator.h"
 #include <string.h>
 #include <stdlib.h>
 #include <assert.h>
+#include <stdarg.h>
+#include <sys/syscall.h>
 
+#define MAX_CUSTOM_BUILTIN_COUNT 128
+static Node *custom_builtins[MAX_CUSTOM_BUILTIN_COUNT];
+static i64 custom_builtins_count = 0;
 
-#define MAX_BUILTINS_COUNT 128
-static Node *all_builtins[MAX_BUILTINS_COUNT];
-static i64 builtins_count = 0;
+#define MAX_SYSCALL_BUILTIN_COUNT 256
+static Node *syscall_builtins[MAX_SYSCALL_BUILTIN_COUNT];
+static i64 syscall_builtins_count = 0;
 
 static void push_builtin(Node *node)
 {
-    assert(builtins_count < MAX_BUILTINS_COUNT);
-    all_builtins[builtins_count++] = node;
+    assert(custom_builtins_count < MAX_CUSTOM_BUILTIN_COUNT);
+    custom_builtins[custom_builtins_count++] = node;
+}
+
+static void make_syscall(int num_args, i64 syscall_num, char *name, Type *return_type, ...)
+{
+    Node *node = Node_new(AST_BUILTIN);
+    node->func.name = name;
+    node->func.return_type = return_type;
+    node->func.num_args = num_args;
+    node->func.args = calloc(sizeof(Variable), num_args);
+
+    // This is a hack to get around the fact that we can't pass a variable
+    // Luckily, we don't actually use this field for the builtins anyway.
+    node->func.max_locals_size = syscall_num;
+
+    va_list ap;
+    va_start(ap, return_type);
+    for (i64 i = 0; i < num_args; i++)
+    {
+        Type *typ = va_arg(ap, Type *);
+        if (!typ) {
+            fprintf(stderr, "Error: Builtin %s has no type for argument %lld\n", name, i);
+            exit(1);
+        }
+        node->func.args[i] = (Variable){"arg", typ, 0};
+    }
+    va_end(ap);
+
+    assert(syscall_builtins_count < MAX_SYSCALL_BUILTIN_COUNT);
+    syscall_builtins[syscall_builtins_count++] = node;
 }
 
 void initialize_builtins()
@@ -28,22 +63,87 @@ void initialize_builtins()
     node->func.args[0] = (Variable){"val", type_new(TYPE_ANY), 0};
     push_builtin(node);
 
-    node = Node_new(AST_BUILTIN);
-    node->func.name = "write";
-    node->func.return_type = type_new(TYPE_INT);
-    node->func.num_args = 3;
-    node->func.args = (Variable *)calloc(sizeof(Variable), 3);
-    node->func.args[0] = (Variable){"fd", type_new(TYPE_INT), 0};
-    node->func.args[1] = (Variable){"buf", type_new_ptr(TYPE_CHAR), 0}; 
-    node->func.args[2] = (Variable){"size", type_new(TYPE_INT), 0};
-    push_builtin(node);
+    make_syscall(3, SYS_write, "write", type_new(TYPE_INT),
+        type_new(TYPE_INT), type_new_ptr(TYPE_CHAR), type_new(TYPE_INT) // Args
+    );
+    make_syscall(3, SYS_read, "read", type_new(TYPE_INT),
+        type_new(TYPE_INT), type_new_ptr(TYPE_CHAR), type_new(TYPE_INT) // Args
+    );
 }
 
 Node *find_builtin_function(Token *token)
 {
-    for (i64 i = 0; i < builtins_count; i++) {
-        if (strcmp(all_builtins[i]->func.name, token->value.as_string) == 0)
-            return all_builtins[i];
+    for (i64 i = 0; i < custom_builtins_count; i++) {
+        if (strcmp(custom_builtins[i]->func.name, token->value.as_string) == 0)
+            return custom_builtins[i];
+    }
+    for (i64 i = 0; i < syscall_builtins_count; i++) {
+        if (strcmp(syscall_builtins[i]->func.name, token->value.as_string) == 0)
+            return syscall_builtins[i];
     }
     return NULL;
+}
+
+char *x86_64_syscall_regs[10] = {
+    "rdi", "rsi", "rdx", "rcx", "r8", "r9", "r10", "r11", "r12", "r13"
+};
+
+static void generate_syscall_builtins(FILE *out)
+{
+    for (i64 i = 0; i < syscall_builtins_count; i++) {
+        Node *node = syscall_builtins[i];
+        fprintf(out, "func_%s:\n", node->func.name);
+        for (i64 i = 0; i < node->func.num_args; i++)
+            fprintf(out, "    mov %s, [rsp+%lld]\n", x86_64_syscall_regs[i], (i+1) * 8);
+        generate_syscall(node->func.max_locals_size, out);
+        fprintf(out, "    ret\n");
+    }
+}
+
+static void generate_custom_builtins(FILE *out)
+{
+    // Stolen shamelessly from tsoding/porth:
+    // https://gitlab.com/tsoding/porth
+    fprintf(out,
+        "func_print:\n"
+        "    mov rdi, [rsp+8]\n"
+        "    mov r9, -3689348814741910323\n"
+        "    sub rsp, 40\n"
+        "    mov BYTE [rsp+31], 10\n"
+        "    lea rcx, [rsp+30]\n"
+        "    mov qword rbx, 0\n"
+        ".L2:\n"
+        "    mov rax, rdi\n"
+        "    lea r8, [rsp+32]\n"
+        "    mul r9\n"
+        "    mov rax, rdi\n"
+        "    sub r8, rcx\n"
+        "    shr rdx, 3\n"
+        "    lea rsi, [rdx+rdx*4]\n"
+        "    add rsi, rsi\n"
+        "    sub rax, rsi\n"
+        "    add eax, 48\n"
+        "    mov BYTE [rcx], al\n"
+        "    mov rax, rdi\n"
+        "    mov rdi, rdx\n"
+        "    mov rdx, rcx\n"
+        "    sub rcx, 1\n"
+        "    cmp rax, 9\n"
+        "    ja .L2\n"
+        "    lea rax, [rsp+32]\n"
+        "    mov edi, 1\n"
+        "    sub rdx, rax\n"
+        "    xor eax, eax\n"
+        "    lea rsi, [rsp+32+rdx]\n"
+        "    mov rdx, r8\n"
+    );
+    generate_syscall(SYS_write, out);
+    fprintf(out, "    add rsp, 40\n");
+    fprintf(out, "    ret\n");
+}
+
+void generate_builtins(FILE *out)
+{
+    generate_custom_builtins(out);
+    generate_syscall_builtins(out);
 }
\ No newline at end of file