Add goroutines and function pointers

src/runtime/runtime.ll

@@ -2,9 +2,26 @@ source_filename = "runtime/runtime.ll"
 
 declare void @runtime.initAll()
 declare void @main.main()
+declare i8* @main.main$async(i8*)
+declare void @runtime.scheduler(i8*)
+
+; Will be changed to true if there are 'go' statements in the compiled program.
+@.has_scheduler = private unnamed_addr constant i1 false
 
 define i32 @main() {
 	call void @runtime.initAll()
+	%has_scheduler = load i1, i1* @.has_scheduler
+	; This branch will be optimized away. Only one of the targets will remain.
+	br i1 %has_scheduler, label %with_scheduler, label %without_scheduler
+
+with_scheduler:
+	; Initialize main and run the scheduler.
+	%main = call i8* @main.main$async(i8* null)
+	call void @runtime.scheduler(i8* %main)
+	ret i32 0
+
+without_scheduler:
+	; No scheduler is necessary. Call main directly.
 	call void @main.main()
 	ret i32 0
 }