[experimental] Allow for RLIBs to only contain metadata.

src/bootstrap/bin/rustc.rs

@@ -253,6 +253,11 @@ fn main() {
         if env::var_os("RUSTC_FORCE_UNSTABLE").is_some() {
             cmd.arg("-Z").arg("force-unstable-if-unmarked");
         }
+
+        // Don't use MIR only RLIBs for the compiler yet
+        if stage != "0" {
+            cmd.arg("-Zmir-only-rlibs=no");
+        }
     } else {
         // Override linker if necessary.
         if let Ok(host_linker) = env::var("RUSTC_HOST_LINKER") {

src/librustc/dep_graph/dep_node.rs

@@ -625,7 +625,7 @@ define_dep_nodes!( <'tcx>
     [eval_always] CollectAndPartitionTranslationItems,
     [] ExportName(DefId),
     [] ContainsExternIndicator(DefId),
-    [] IsTranslatedFunction(DefId),
+    [] IsTranslatedItem(DefId),
     [] CodegenUnit(InternedString),
     [] CompileCodegenUnit(InternedString),
     [input] OutputFilenames,
@@ -642,6 +642,7 @@ define_dep_nodes!( <'tcx>
 
     [] GetSymbolExportLevel(DefId),
 
+    [input] IsMirOnlyRlib(CrateNum),
 );
 
 trait DepNodeParams<'a, 'gcx: 'tcx + 'a, 'tcx: 'a> : fmt::Debug {

src/librustc/hir/map/mod.rs

@@ -22,6 +22,7 @@ use hir::def_id::{CRATE_DEF_INDEX, DefId, LocalDefId, DefIndexAddressSpace};
 use syntax::abi::Abi;
 use syntax::ast::{self, Name, NodeId, CRATE_NODE_ID};
 use syntax::codemap::Spanned;
+use syntax::ext::base::MacroKind;
 use syntax_pos::Span;
 
 use hir::*;
@@ -32,13 +33,15 @@ use util::nodemap::{DefIdMap, FxHashMap};
 use arena::TypedArena;
 use std::cell::RefCell;
 use std::io;
+use ty::TyCtxt;
 
 pub mod blocks;
 mod collector;
 mod def_collector;
 pub mod definitions;
 mod hir_id_validator;
 
+
 pub const ITEM_LIKE_SPACE: DefIndexAddressSpace = DefIndexAddressSpace::Low;
 pub const REGULAR_SPACE: DefIndexAddressSpace = DefIndexAddressSpace::High;
 
@@ -373,6 +376,92 @@ impl<'hir> Map<'hir> {
         self.definitions.as_local_node_id(def_id.to_def_id()).unwrap()
     }
 
+    pub fn describe_def(&self, node_id: NodeId) -> Option<Def> {
+        let node = if let Some(node) = self.find(node_id) {
+            node
+        } else {
+            return None
+        };
+
+        match node {
+            NodeItem(item) => {
+                let def_id = || {
+                    self.local_def_id(item.id)
+                };
+
+                match item.node {
+                    ItemStatic(_, m, _) => Some(Def::Static(def_id(),
+                                                            m == MutMutable)),
+                    ItemConst(..) => Some(Def::Const(def_id())),
+                    ItemFn(..) => Some(Def::Fn(def_id())),
+                    ItemMod(..) => Some(Def::Mod(def_id())),
+                    ItemGlobalAsm(..) => Some(Def::GlobalAsm(def_id())),
+                    ItemTy(..) => Some(Def::TyAlias(def_id())),
+                    ItemEnum(..) => Some(Def::Enum(def_id())),
+                    ItemStruct(..) => Some(Def::Struct(def_id())),
+                    ItemUnion(..) => Some(Def::Union(def_id())),
+                    ItemTrait(..) => Some(Def::Trait(def_id())),
+                    ItemTraitAlias(..) => {
+                        bug!("trait aliases are not yet implemented (see issue #41517)")
+                    },
+                    ItemExternCrate(_) |
+                    ItemUse(..) |
+                    ItemForeignMod(..) |
+                    ItemImpl(..) => None,
+                }
+            }
+            NodeForeignItem(item) => {
+                let def_id = self.local_def_id(item.id);
+                match item.node {
+                    ForeignItemFn(..) => Some(Def::Fn(def_id)),
+                    ForeignItemStatic(_, m) => Some(Def::Static(def_id, m)),
+                    ForeignItemType => Some(Def::TyForeign(def_id)),
+                }
+            }
+            NodeTraitItem(item) => {
+                let def_id = self.local_def_id(item.id);
+                match item.node {
+                    TraitItemKind::Const(..) => Some(Def::AssociatedConst(def_id)),
+                    TraitItemKind::Method(..) => Some(Def::Method(def_id)),
+                    TraitItemKind::Type(..) => Some(Def::AssociatedTy(def_id)),
+                }
+            }
+            NodeImplItem(item) => {
+                let def_id = self.local_def_id(item.id);
+                match item.node {
+                    ImplItemKind::Const(..) => Some(Def::AssociatedConst(def_id)),
+                    ImplItemKind::Method(..) => Some(Def::Method(def_id)),
+                    ImplItemKind::Type(..) => Some(Def::AssociatedTy(def_id)),
+                }
+            }
+            NodeVariant(variant) => {
+                let def_id = self.local_def_id(variant.node.data.id());
+                Some(Def::Variant(def_id))
+            }
+            NodeField(_) |
+            NodeExpr(_) |
+            NodeStmt(_) |
+            NodeTy(_) |
+            NodeTraitRef(_) |
+            NodePat(_) |
+            NodeBinding(_) |
+            NodeStructCtor(_) |
+            NodeLifetime(_) |
+            NodeVisibility(_) |
+            NodeBlock(_) => None,
+            NodeLocal(local) => {
+                Some(Def::Local(local.id))
+            }
+            NodeMacroDef(macro_def) => {
+                Some(Def::Macro(self.local_def_id(macro_def.id),
+                                MacroKind::Bang))
+            }
+            NodeTyParam(param) => {
+                Some(Def::TyParam(self.local_def_id(param.id)))
+            }
+        }
+    }
+
     fn entry_count(&self) -> usize {
         self.map.len()
     }
@@ -1275,3 +1364,12 @@ fn node_id_to_string(map: &Map, id: NodeId, include_id: bool) -> String {
         }
     }
 }
+
+pub fn describe_def(tcx: TyCtxt, def_id: DefId) -> Option<Def> {
+    if let Some(node_id) = tcx.hir.as_local_node_id(def_id) {
+        tcx.hir.describe_def(node_id)
+    } else {
+        bug!("Calling local describe_def query provider for upstream DefId: {:?}",
+             def_id)
+    }
+}

src/librustc/hir/mod.rs

@@ -43,6 +43,7 @@ use syntax::tokenstream::TokenStream;
 use syntax::util::ThinVec;
 use syntax::util::parser::ExprPrecedence;
 use ty::AdtKind;
+use ty::maps::Providers;
 
 use rustc_data_structures::indexed_vec;
 
@@ -2204,3 +2205,8 @@ pub type TraitMap = NodeMap<Vec<TraitCandidate>>;
 // Map from the NodeId of a glob import to a list of items which are actually
 // imported.
 pub type GlobMap = NodeMap<FxHashSet<Name>>;
+
+
+pub fn provide(providers: &mut Providers) {
+    providers.describe_def = map::describe_def;
+}

src/librustc/mir/mono.rs

@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use hir::def_id::DefId;
 use syntax::ast::NodeId;
 use syntax::symbol::InternedString;
 use ty::{Instance, TyCtxt};
@@ -21,7 +22,7 @@ use std::hash::Hash;
 #[derive(PartialEq, Eq, Clone, Copy, Debug, Hash)]
 pub enum MonoItem<'tcx> {
     Fn(Instance<'tcx>),
-    Static(NodeId),
+    Static(DefId),
     GlobalAsm(NodeId),
 }
 
@@ -50,7 +51,9 @@ impl<'tcx> HashStable<StableHashingContext<'tcx>> for MonoItem<'tcx> {
             MonoItem::Fn(ref instance) => {
                 instance.hash_stable(hcx, hasher);
             }
-            MonoItem::Static(node_id)    |
+            MonoItem::Static(def_id) => {
+                def_id.hash_stable(hcx, hasher);
+            }
             MonoItem::GlobalAsm(node_id) => {
                 hcx.with_node_id_hashing_mode(NodeIdHashingMode::HashDefPath, |hcx| {
                     node_id.hash_stable(hcx, hasher);

src/librustc/session/config.rs

@@ -1322,6 +1322,8 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
          epoch). Crates compiled with different epochs can be linked together."),
     run_dsymutil: Option<bool> = (None, parse_opt_bool, [TRACKED],
           "run `dsymutil` and delete intermediate object files"),
+
+    mir_only_rlibs: Option<bool> = (Some(true), parse_opt_bool, [TRACKED], "go!"),
 }
 
 pub fn default_lib_output() -> CrateType {

src/librustc/ty/maps/config.rs

@@ -50,6 +50,13 @@ impl<'tcx, M: QueryConfig<Key=DefId>> QueryDescription<'tcx> for M {
     }
 }
 
+
+impl<'tcx> QueryDescription<'tcx> for queries::is_mir_only_rlib<'tcx> {
+    fn describe(_tcx: TyCtxt, cnum: CrateNum) -> String {
+        format!("computing whether `{}` is a MIR-only RLIB", cnum)
+    }
+}
+
 impl<'tcx> QueryDescription<'tcx> for queries::is_copy_raw<'tcx> {
     fn describe(_tcx: TyCtxt, env: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> String {
         format!("computing whether `{}` is `Copy`", env.value)

src/librustc/ty/maps/mod.rs

@@ -349,7 +349,7 @@ define_maps! { <'tcx>
     [] fn export_name: ExportName(DefId) -> Option<Symbol>,
     [] fn contains_extern_indicator: ContainsExternIndicator(DefId) -> bool,
     [] fn symbol_export_level: GetSymbolExportLevel(DefId) -> SymbolExportLevel,
-    [] fn is_translated_function: IsTranslatedFunction(DefId) -> bool,
+    [] fn is_translated_item: IsTranslatedItem(DefId) -> bool,
     [] fn codegen_unit: CodegenUnit(InternedString) -> Arc<CodegenUnit<'tcx>>,
     [] fn compile_codegen_unit: CompileCodegenUnit(InternedString) -> Stats,
     [] fn output_filenames: output_filenames_node(CrateNum)
@@ -374,6 +374,8 @@ define_maps! { <'tcx>
     // Get an estimate of the size of an InstanceDef based on its MIR for CGU partitioning.
     [] fn instance_def_size_estimate: instance_def_size_estimate_dep_node(ty::InstanceDef<'tcx>)
         -> usize,
+
+    [] fn is_mir_only_rlib: IsMirOnlyRlib(CrateNum) -> bool,
 }
 
 //////////////////////////////////////////////////////////////////////

src/librustc/ty/maps/plumbing.rs

@@ -929,13 +929,14 @@ pub fn force_from_dep_node<'a, 'gcx, 'lcx>(tcx: TyCtxt<'a, 'gcx, 'lcx>,
         DepKind::ContainsExternIndicator => {
             force!(contains_extern_indicator, def_id!());
         }
-        DepKind::IsTranslatedFunction => { force!(is_translated_function, def_id!()); }
+        DepKind::IsTranslatedItem => { force!(is_translated_item, def_id!()); }
         DepKind::OutputFilenames => { force!(output_filenames, LOCAL_CRATE); }
 
         DepKind::TargetFeaturesWhitelist => { force!(target_features_whitelist, LOCAL_CRATE); }
         DepKind::TargetFeaturesEnabled => { force!(target_features_enabled, def_id!()); }
 
         DepKind::GetSymbolExportLevel => { force!(symbol_export_level, def_id!()); }
+        DepKind::IsMirOnlyRlib => { force!(is_mir_only_rlib, krate!()); }
     }
 
     true

src/librustc_driver/driver.rs

@@ -929,6 +929,7 @@ pub fn phase_2_configure_and_expand_inner<'a, F>(sess: &'a Session,
 }
 
 pub fn default_provide(providers: &mut ty::maps::Providers) {
+    hir::provide(providers);
     borrowck::provide(providers);
     mir::provide(providers);
     reachable::provide(providers);

src/librustc_metadata/cstore_impl.rs

@@ -237,6 +237,8 @@ provide! { <'tcx> tcx, def_id, other, cdata,
 
     has_copy_closures => { cdata.has_copy_closures(tcx.sess) }
     has_clone_closures => { cdata.has_clone_closures(tcx.sess) }
+
+    is_mir_only_rlib => { cdata.root.is_mir_only_rlib }
 }
 
 pub fn provide<'tcx>(providers: &mut Providers<'tcx>) {

src/librustc_metadata/encoder.rs

@@ -415,6 +415,14 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
         let has_default_lib_allocator =
             attr::contains_name(tcx.hir.krate_attrs(), "default_lib_allocator");
         let has_global_allocator = tcx.sess.has_global_allocator.get();
+
+        let is_mir_only_rlib = if tcx.sess.opts.debugging_opts.mir_only_rlibs != Some(false) {
+            let crate_types = tcx.sess.crate_types.borrow();
+            crate_types.len() == 1 && crate_types[0] == config::CrateTypeRlib
+        } else {
+            false
+        };
+
         let root = self.lazy(&CrateRoot {
             name: tcx.crate_name(LOCAL_CRATE),
             triple: tcx.sess.opts.target_triple.clone(),
@@ -423,6 +431,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             panic_strategy: tcx.sess.panic_strategy(),
             has_global_allocator: has_global_allocator,
             has_default_lib_allocator: has_default_lib_allocator,
+            is_mir_only_rlib,
             plugin_registrar_fn: tcx.sess
                 .plugin_registrar_fn
                 .get()
@@ -833,7 +842,8 @@ impl<'a, 'b: 'a, 'tcx: 'b> IsolatedEncoder<'a, 'b, 'tcx> {
             let needs_inline = types > 0 || attr::requests_inline(&ast_item.attrs);
             let is_const_fn = sig.constness == hir::Constness::Const;
             let ast = if is_const_fn { Some(body) } else { None };
-            let always_encode_mir = self.tcx.sess.opts.debugging_opts.always_encode_mir;
+            let always_encode_mir = self.tcx.sess.opts.debugging_opts.always_encode_mir ||
+                                    self.tcx.sess.opts.debugging_opts.mir_only_rlibs != Some(false);
             (ast, needs_inline || is_const_fn || always_encode_mir)
         } else {
             (None, false)
@@ -1115,14 +1125,16 @@ impl<'a, 'b: 'a, 'tcx: 'b> IsolatedEncoder<'a, 'b, 'tcx> {
                 _ => None,
             },
             mir: match item.node {
-                hir::ItemStatic(..) if self.tcx.sess.opts.debugging_opts.always_encode_mir => {
+                hir::ItemStatic(..) if self.tcx.sess.opts.debugging_opts.always_encode_mir ||
+                            self.tcx.sess.opts.debugging_opts.mir_only_rlibs != Some(false) => {
                     self.encode_optimized_mir(def_id)
                 }
                 hir::ItemConst(..) => self.encode_optimized_mir(def_id),
                 hir::ItemFn(_, _, constness, _, ref generics, _) => {
                     let has_tps = generics.ty_params().next().is_some();
                     let needs_inline = has_tps || attr::requests_inline(&item.attrs);
-                    let always_encode_mir = self.tcx.sess.opts.debugging_opts.always_encode_mir;
+                    let always_encode_mir = self.tcx.sess.opts.debugging_opts.always_encode_mir ||
+                                self.tcx.sess.opts.debugging_opts.mir_only_rlibs != Some(false);
                     if needs_inline || constness == hir::Constness::Const || always_encode_mir {
                         self.encode_optimized_mir(def_id)
                     } else {

src/librustc_metadata/schema.rs

@@ -191,6 +191,7 @@ pub struct CrateRoot {
     pub panic_strategy: PanicStrategy,
     pub has_global_allocator: bool,
     pub has_default_lib_allocator: bool,
+    pub is_mir_only_rlib: bool,
     pub plugin_registrar_fn: Option<DefIndex>,
     pub macro_derive_registrar: Option<DefIndex>,