nac3artiq: demote global value to private

... except typeinfo & now symbols.
typeinfo will be read by the runtime linker; now is for now-pinning.

nac3artiq/src/lib.rs

@@ -6,6 +6,7 @@ use std::sync::Arc;
 
 use inkwell::{
     memory_buffer::MemoryBuffer,
+    module::Linkage,
     passes::{PassManager, PassManagerBuilder},
     targets::*,
     OptimizationLevel,
@@ -822,6 +823,19 @@ impl Nac3 {
             function_iter = func.get_next_function();
         }
 
+        // Demote all global variables that will not be referenced in the kernel to private
+        let preserved_symbols: Vec<&'static [u8]> = vec![
+            b"typeinfo",
+            b"now",
+        ];
+        let mut global_option = main.get_first_global();
+        while let Some(global) = global_option {
+            if !preserved_symbols.contains(&(global.get_name().to_bytes())) {
+                global.set_linkage(Linkage::Private);
+            }
+            global_option = global.get_next_global();
+        }
+
         let builder = PassManagerBuilder::create();
         builder.set_optimization_level(OptimizationLevel::Aggressive);
         let passes = PassManager::create(());