Compute LLVM-agnostic type layouts in rustc.

# Conflicts:
#	src/librustc/ty/layout.rs

Author: eddyb

src/librustc/ty/context.rs

@@ -31,7 +31,7 @@ use hir::FreevarMap;
 use ty::{BareFnTy, InferTy, ParamTy, ProjectionTy, TraitTy};
 use ty::{TyVar, TyVid, IntVar, IntVid, FloatVar, FloatVid};
 use ty::TypeVariants::*;
-use ty::layout::TargetDataLayout;
+use ty::layout::{Layout, TargetDataLayout};
 use ty::maps;
 use util::common::MemoizationMap;
 use util::nodemap::{NodeMap, NodeSet, DefIdMap, DefIdSet};
@@ -56,6 +56,7 @@ pub struct CtxtArenas<'tcx> {
     bare_fn: TypedArena<BareFnTy<'tcx>>,
     region: TypedArena<Region>,
     stability: TypedArena<attr::Stability>,
+    layout: TypedArena<Layout>,
 
     // references
     trait_defs: TypedArena<ty::TraitDef<'tcx>>,
@@ -70,6 +71,7 @@ impl<'tcx> CtxtArenas<'tcx> {
             bare_fn: TypedArena::new(),
             region: TypedArena::new(),
             stability: TypedArena::new(),
+            layout: TypedArena::new(),
 
             trait_defs: TypedArena::new(),
             adt_defs: TypedArena::new()
@@ -230,6 +232,7 @@ pub struct TyCtxt<'tcx> {
     bare_fn_interner: RefCell<FnvHashMap<&'tcx BareFnTy<'tcx>, &'tcx BareFnTy<'tcx>>>,
     region_interner: RefCell<FnvHashMap<&'tcx Region, &'tcx Region>>,
     stability_interner: RefCell<FnvHashMap<&'tcx attr::Stability, &'tcx attr::Stability>>,
+    layout_interner: RefCell<FnvHashMap<&'tcx Layout, &'tcx Layout>>,
 
     pub dep_graph: DepGraph,
 
@@ -423,6 +426,9 @@ pub struct TyCtxt<'tcx> {
 
     /// Data layout specification for the current target.
     pub data_layout: TargetDataLayout,
+
+    /// Cache for layouts computed from types.
+    pub layout_cache: RefCell<FnvHashMap<Ty<'tcx>, &'tcx Layout>>,
 }
 
 impl<'tcx> TyCtxt<'tcx> {
@@ -504,6 +510,20 @@ impl<'tcx> TyCtxt<'tcx> {
         interned
     }
 
+    pub fn intern_layout(&self, layout: Layout) -> &'tcx Layout {
+        if let Some(layout) = self.layout_interner.borrow().get(&layout) {
+            return layout;
+        }
+
+        let interned = self.arenas.layout.alloc(layout);
+        if let Some(prev) = self.layout_interner
+                                .borrow_mut()
+                                .insert(interned, interned) {
+            bug!("Tried to overwrite interned Layout: {:?}", prev)
+        }
+        interned
+    }
+
     pub fn store_free_region_map(&self, id: NodeId, map: FreeRegionMap) {
         if self.free_region_maps.borrow_mut().insert(id, map).is_some() {
             bug!("Tried to overwrite interned FreeRegionMap for NodeId {:?}", id)
@@ -547,6 +567,7 @@ impl<'tcx> TyCtxt<'tcx> {
             bare_fn_interner: RefCell::new(FnvHashMap()),
             region_interner: RefCell::new(FnvHashMap()),
             stability_interner: RefCell::new(FnvHashMap()),
+            layout_interner: RefCell::new(FnvHashMap()),
             dep_graph: dep_graph.clone(),
             types: common_types,
             named_region_map: named_region_map,
@@ -595,6 +616,7 @@ impl<'tcx> TyCtxt<'tcx> {
             fragment_infos: RefCell::new(DefIdMap()),
             crate_name: token::intern_and_get_ident(crate_name),
             data_layout: data_layout,
+            layout_cache: RefCell::new(FnvHashMap()),
        }, f)
     }
 }
@@ -768,6 +790,7 @@ impl<'tcx> TyCtxt<'tcx> {
         println!("BareFnTy interner: #{}", self.bare_fn_interner.borrow().len());
         println!("Region interner: #{}", self.region_interner.borrow().len());
         println!("Stability interner: #{}", self.stability_interner.borrow().len());
+        println!("Layout interner: #{}", self.layout_interner.borrow().len());
     }
 }