incr.comp.: Take names of children into account when computing the IC…

…H of a module's HIR.

src/librustc/ich/impls_hir.rs

@@ -756,13 +756,28 @@ impl_stable_hash_for!(enum hir::ImplPolarity {
     Negative
 });
 
-impl_stable_hash_for!(struct hir::Mod {
-    inner,
-    // We are not hashing the IDs of the items contained in the module.
-    // This is harmless and matches the current behavior but it's not
-    // actually correct. See issue #40876.
-    item_ids -> _,
-});
+impl<'a> HashStable<StableHashingContext<'a>> for hir::Mod {
+    fn hash_stable<W: StableHasherResult>(&self,
+                                          hcx: &mut StableHashingContext<'a>,
+                                          hasher: &mut StableHasher<W>) {
+        let hir::Mod {
+            inner: ref inner_span,
+            ref item_ids,
+        } = *self;
+
+        inner_span.hash_stable(hcx, hasher);
+
+        let mut item_ids: Vec<DefPathHash> = item_ids.iter().map(|id| {
+            let (def_path_hash, local_id) = id.id.to_stable_hash_key(hcx);
+            debug_assert_eq!(local_id, hir::ItemLocalId(0));
+            def_path_hash
+        }).collect();
+
+        item_ids.sort_unstable();
+
+        item_ids.hash_stable(hcx, hasher);
+    }
+}
 
 impl_stable_hash_for!(struct hir::ForeignMod {
     abi,

src/librustc_codegen_llvm/mono_item.rs

@@ -25,11 +25,10 @@ use monomorphize::Instance;
 use type_of::LayoutLlvmExt;
 use rustc::hir;
 use rustc::hir::def::Def;
-use rustc::hir::def_id::DefId;
+use rustc::hir::def_id::{DefId, LOCAL_CRATE};
 use rustc::mir::mono::{Linkage, Visibility};
 use rustc::ty::TypeFoldable;
 use rustc::ty::layout::LayoutOf;
-use syntax::attr;
 use std::fmt;
 
 pub use rustc::mir::mono::MonoItem;
@@ -173,7 +172,7 @@ fn predefine_fn<'a, 'tcx>(cx: &CodegenCx<'a, 'tcx>,
     // visibility as we're going to link this object all over the place but
     // don't want the symbols to get exported.
     if linkage != Linkage::Internal && linkage != Linkage::Private &&
-       attr::contains_name(cx.tcx.hir.krate_attrs(), "compiler_builtins") {
+       cx.tcx.is_compiler_builtins(LOCAL_CRATE) {
         unsafe {
             llvm::LLVMRustSetVisibility(lldecl, llvm::Visibility::Hidden);
         }