libia2: WIP stack alignment

runtime/libia2/threads.c

@@ -62,7 +62,6 @@ void *ia2_thread_begin(void *arg) {
       : [fn] "r"(fn), [data] "r"(data), [new_sp_addr] "r"(new_sp_addr)
       : "rdi");
 #elif defined(__aarch64__)
-#warning "ia2_thread_begin does not align the stack correctly"
   __asm__ volatile(
         // Copy stack pointer to x10
         "mov x10, sp\n"
@@ -71,6 +70,12 @@ void *ia2_thread_begin(void *arg) {
         "mov sp, x0\n"
         // Push the old stack pointer
         "str x10, [sp, #-8]!\n"
+        // Align the stack
+        //"movn x10, #0x000f\n"
+        //"and sp, sp, x10, #0\n"
+        // Prologue (necessary?)
+        //"str x29, [sp, #-8]!\n"
+        //"mov x29, sp\n"
         // Load argument
         "ldr x0, [%[data]]\n"
         // Call fn(data)
@@ -84,6 +89,8 @@ void *ia2_thread_begin(void *arg) {
       : [result] "=r"(result)
       : [fn] "r"(fn), [data] "r"(&data), [new_sp_addr] "r"(new_sp_addr)
       : "x0", "x10");
+#else
+#error "unknown architecture"
 #endif
   /* clang-format on */