Implement nested and mutable statics (fixes rust-lang#9)

Author: bjorn3

examples/mini_core.rs

@@ -44,6 +44,7 @@ unsafe impl Sync for i16 {}
 unsafe impl Sync for i32 {}
 unsafe impl Sync for isize {}
 unsafe impl Sync for char {}
+unsafe impl<'a, T: ?Sized> Sync for &'a T {}
 
 #[lang = "freeze"]
 trait Freeze {}

examples/mini_core_hello_world.rs

@@ -16,7 +16,8 @@ extern "C" {
     fn puts(s: *const u8);
 }
 
-static NUM: u8 = 6 * 7;
+static mut NUM: u8 = 6 * 7;
+static NUM_REF: &'static u8 = unsafe { &NUM };
 
 #[lang = "start"]
 fn start(_main: *const u8, i: isize, _: *const *const u8) -> isize {
@@ -25,5 +26,8 @@ fn start(_main: *const u8, i: isize, _: *const *const u8) -> isize {
         puts(ptr);
     }
 
-    NUM as isize
+    unsafe {
+        NUM = 43;
+        *NUM_REF as isize
+    }
 }

src/constant.rs

@@ -1,6 +1,7 @@
 use cranelift_module::*;
 use crate::prelude::*;
-use rustc::mir::interpret::{read_target_uint, AllocId, ConstValue, GlobalId};
+use syntax::ast::Mutability as AstMutability;
+use rustc::mir::interpret::{read_target_uint, AllocId, AllocType, ConstValue, GlobalId};
 use rustc::ty::Const;
 use rustc_mir::interpret::{CompileTimeEvaluator, Memory};
 
@@ -191,12 +192,24 @@ fn define_all_allocs<'a, 'tcx: 'a, B: Backend + 'a>(
 
         data_ctx.define(
             alloc.bytes.to_vec().into_boxed_slice(),
-            Writability::Readonly,
+            match alloc.runtime_mutability {
+                AstMutability::Mutable => Writability::Writable,
+                AstMutability::Immutable => Writability::Readonly,
+            },
         );
 
         for &(offset, reloc) in alloc.relocations.iter() {
-            cx.todo.insert(TodoItem::Alloc(reloc));
-            let data_id = data_id_for_alloc_id(module, reloc);
+            let data_id = match tcx.alloc_map.lock().get(reloc).unwrap() {
+                AllocType::Memory(_) => {
+                    cx.todo.insert(TodoItem::Alloc(reloc));
+                    data_id_for_alloc_id(module, reloc)
+                }
+                AllocType::Function(_) => unimplemented!("function static reference"),
+                AllocType::Static(def_id) => {
+                    cx.todo.insert(TodoItem::Static(def_id));
+                    data_id_for_static(tcx, module, def_id)
+                }
+            };
 
             let reloc_offset = {
                 let endianness = memory.endianness();