Auto merge of #41469 - arielb1:rustc-spring-cleaning, r=eddyb

Performance audit, Spring 2017

Fix up some quite important performance "surprises" I've found running callgrind on rustc.

Author: bors

src/liballoc/heap.rs

@@ -16,7 +16,6 @@
             issue = "27700")]
 
 use core::{isize, usize};
-#[cfg(not(test))]
 use core::intrinsics::{min_align_of_val, size_of_val};
 
 #[allow(improper_ctypes)]
@@ -158,10 +157,9 @@ unsafe fn exchange_malloc(size: usize, align: usize) -> *mut u8 {
     }
 }
 
-#[cfg(not(test))]
-#[lang = "box_free"]
+#[cfg_attr(not(test), lang = "box_free")]
 #[inline]
-unsafe fn box_free<T: ?Sized>(ptr: *mut T) {
+pub(crate) unsafe fn box_free<T: ?Sized>(ptr: *mut T) {
     let size = size_of_val(&*ptr);
     let align = min_align_of_val(&*ptr);
     // We do not allocate for Box<T> when T is ZST, so deallocation is also not necessary.

src/liballoc/lib.rs

@@ -87,6 +87,7 @@
 #![feature(needs_allocator)]
 #![feature(optin_builtin_traits)]
 #![feature(placement_in_syntax)]
+#![cfg_attr(stage0, feature(pub_restricted))]
 #![feature(shared)]
 #![feature(staged_api)]
 #![feature(unboxed_closures)]

src/liballoc/rc.rs

@@ -239,7 +239,7 @@ use core::ops::CoerceUnsized;
 use core::ptr::{self, Shared};
 use core::convert::From;
 
-use heap::deallocate;
+use heap::{allocate, deallocate, box_free};
 use raw_vec::RawVec;
 
 struct RcBox<T: ?Sized> {
@@ -248,7 +248,6 @@ struct RcBox<T: ?Sized> {
     value: T,
 }
 
-
 /// A single-threaded reference-counting pointer.
 ///
 /// See the [module-level documentation](./index.html) for more details.
@@ -438,6 +437,38 @@ impl Rc<str> {
     }
 }
 
+impl<T> Rc<[T]> {
+    /// Constructs a new `Rc<[T]>` from a `Box<[T]>`.
+    #[doc(hidden)]
+    #[unstable(feature = "rustc_private",
+               reason = "for internal use in rustc",
+               issue = "0")]
+    pub fn __from_array(value: Box<[T]>) -> Rc<[T]> {
+        unsafe {
+            let ptr: *mut RcBox<[T]> =
+                mem::transmute([mem::align_of::<RcBox<[T; 1]>>(), value.len()]);
+            // FIXME(custom-DST): creating this invalid &[T] is dubiously defined,
+            // we should have a better way of getting the size/align
+            // of a DST from its unsized part.
+            let ptr = allocate(size_of_val(&*ptr), align_of_val(&*ptr));
+            let ptr: *mut RcBox<[T]> = mem::transmute([ptr as usize, value.len()]);
+
+            // Initialize the new RcBox.
+            ptr::write(&mut (*ptr).strong, Cell::new(1));
+            ptr::write(&mut (*ptr).weak, Cell::new(1));
+            ptr::copy_nonoverlapping(
+                value.as_ptr(),
+                &mut (*ptr).value as *mut [T] as *mut T,
+                value.len());
+
+            // Free the original allocation without freeing its (moved) contents.
+            box_free(Box::into_raw(value));
+
+            Rc { ptr: Shared::new(ptr as *const _) }
+        }
+    }
+}
+
 impl<T: ?Sized> Rc<T> {
     /// Creates a new [`Weak`][weak] pointer to this value.
     ///

src/librustc/infer/freshen.rs

@@ -99,7 +99,7 @@ impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for TypeFreshener<'a, 'gcx, 'tcx> {
             ty::ReEmpty |
             ty::ReErased => {
                 // replace all free regions with 'erased
-                self.tcx().mk_region(ty::ReErased)
+                self.tcx().types.re_erased
             }
         }
     }

src/librustc/infer/region_inference/mod.rs

@@ -948,7 +948,7 @@ impl<'a, 'gcx, 'tcx> RegionVarBindings<'a, 'gcx, 'tcx> {
                 } else {
                     // otherwise, we don't know what the free region is,
                     // so we must conservatively say the LUB is static:
-                    self.tcx.mk_region(ReStatic)
+                    self.tcx.types.re_static
                 }
             }
 
@@ -971,7 +971,7 @@ impl<'a, 'gcx, 'tcx> RegionVarBindings<'a, 'gcx, 'tcx> {
                 if a == b {
                     a
                 } else {
-                    self.tcx.mk_region(ReStatic)
+                    self.tcx.types.re_static
                 }
             }
         }
@@ -1018,7 +1018,7 @@ impl<'a, 'gcx, 'tcx> RegionVarBindings<'a, 'gcx, 'tcx> {
 
     fn construct_var_data(&self) -> Vec<VarValue<'tcx>> {
         (0..self.num_vars() as usize)
-            .map(|_| Value(self.tcx.mk_region(ty::ReEmpty)))
+            .map(|_| Value(self.tcx.types.re_empty))
             .collect()
     }
 
@@ -1493,7 +1493,7 @@ fn lookup<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
                           -> &'tcx ty::Region {
     match values[rid.index as usize] {
         Value(r) => r,
-        ErrorValue => tcx.mk_region(ReStatic), // Previously reported error.
+        ErrorValue => tcx.types.re_static, // Previously reported error.
     }
 }
 

src/librustc/middle/cstore.rs

@@ -188,14 +188,13 @@ pub trait CrateStore {
     fn visibility(&self, def: DefId) -> ty::Visibility;
     fn visible_parent_map<'a>(&'a self) -> ::std::cell::Ref<'a, DefIdMap<DefId>>;
     fn item_generics_cloned(&self, def: DefId) -> ty::Generics;
-    fn item_attrs(&self, def_id: DefId) -> Vec<ast::Attribute>;
+    fn item_attrs(&self, def_id: DefId) -> Rc<[ast::Attribute]>;
     fn fn_arg_names(&self, did: DefId) -> Vec<ast::Name>;
 
     // trait info
     fn implementations_of_trait(&self, filter: Option<DefId>) -> Vec<DefId>;
 
     // impl info
-    fn impl_polarity(&self, def: DefId) -> hir::ImplPolarity;
     fn impl_parent(&self, impl_def_id: DefId) -> Option<DefId>;
 
     // trait/impl-item info
@@ -323,14 +322,13 @@ impl CrateStore for DummyCrateStore {
     }
     fn item_generics_cloned(&self, def: DefId) -> ty::Generics
         { bug!("item_generics_cloned") }
-    fn item_attrs(&self, def_id: DefId) -> Vec<ast::Attribute> { bug!("item_attrs") }
+    fn item_attrs(&self, def_id: DefId) -> Rc<[ast::Attribute]> { bug!("item_attrs") }
     fn fn_arg_names(&self, did: DefId) -> Vec<ast::Name> { bug!("fn_arg_names") }
 
     // trait info
     fn implementations_of_trait(&self, filter: Option<DefId>) -> Vec<DefId> { vec![] }
 
     // impl info
-    fn impl_polarity(&self, def: DefId) -> hir::ImplPolarity { bug!("impl_polarity") }
     fn impl_parent(&self, def: DefId) -> Option<DefId> { bug!("impl_parent") }
 
     // trait/impl-item info

src/librustc/middle/expr_use_visitor.rs

@@ -426,7 +426,7 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
 
             hir::ExprMatch(ref discr, ref arms, _) => {
                 let discr_cmt = return_if_err!(self.mc.cat_expr(&discr));
-                let r = self.tcx().mk_region(ty::ReEmpty);
+                let r = self.tcx().types.re_empty;
                 self.borrow_expr(&discr, r, ty::ImmBorrow, MatchDiscriminant);
 
                 // treatment of the discriminant is handled while walking the arms.

src/librustc/middle/lang_items.rs

@@ -223,9 +223,10 @@ impl<'a, 'tcx> LanguageItemCollector<'a, 'tcx> {
 
 pub fn extract(attrs: &[ast::Attribute]) -> Option<Symbol> {
     for attribute in attrs {
-        match attribute.value_str() {
-            Some(value) if attribute.check_name("lang") => return Some(value),
-            _ => {}
+        if attribute.check_name("lang") {
+            if let Some(value) = attribute.value_str() {
+                return Some(value)
+            }
         }
     }
 

src/librustc/middle/mem_categorization.rs

@@ -871,8 +871,8 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
         // we can promote to a constant, otherwise equal to enclosing temp
         // lifetime.
         let (re, old_re) = if promotable {
-            (self.tcx().mk_region(ty::ReStatic),
-             self.tcx().mk_region(ty::ReStatic))
+            (self.tcx().types.re_static,
+             self.tcx().types.re_static)
         } else {
             self.temporary_scope(id)
         };

src/librustc/traits/fulfill.rs

@@ -443,7 +443,7 @@ fn process_predicate<'a, 'gcx, 'tcx>(
                         // Otherwise, we have something of the form
                         // `for<'a> T: 'a where 'a not in T`, which we can treat as `T: 'static`.
                         Some(t_a) => {
-                            let r_static = selcx.tcx().mk_region(ty::ReStatic);
+                            let r_static = selcx.tcx().types.re_static;
                             register_region_obligation(t_a, r_static,
                                                        obligation.cause.clone(),
                                                        region_obligations);