alter exchange_free for sized deallocation

The support for sized deallocation is nearly complete. The only known
missing pieces are `Box<str>`, `Box<[T]>` and `proc`.

Author: thestinger

src/liballoc/heap.rs

@@ -9,7 +9,7 @@
 // except according to those terms.
 
 // FIXME: #13994: port to the sized deallocation API when available
-// FIXME: #13996: need a way to mark the `allocate` and `reallocate` return values as `noalias`
+// FIXME: #13996: mark the `allocate` and `reallocate` return value as `noalias` and `nonnull`
 
 use core::intrinsics::{abort, cttz32};
 use core::option::{None, Option};
@@ -133,14 +133,20 @@ unsafe fn exchange_malloc(size: uint, align: uint) -> *mut u8 {
     }
 }
 
-#[cfg(not(test))]
+#[cfg(not(test), stage0)]
 #[lang="exchange_free"]
 #[inline]
-// FIXME: #13994 (rustc should pass align and size here)
 unsafe fn exchange_free(ptr: *mut u8) {
     deallocate(ptr, 0, 8);
 }
 
+#[cfg(not(test), not(stage0))]
+#[lang="exchange_free"]
+#[inline]
+unsafe fn exchange_free(ptr: *mut u8, size: uint, align: uint) {
+    deallocate(ptr, size, align);
+}
+
 // FIXME: #7496
 #[cfg(not(test))]
 #[lang="closure_exchange_malloc"]

src/librustc/middle/trans/cleanup.rs

@@ -278,13 +278,14 @@ impl<'a> CleanupMethods<'a> for FunctionContext<'a> {
     fn schedule_free_value(&self,
                            cleanup_scope: ScopeId,
                            val: ValueRef,
-                           heap: Heap) {
+                           heap: Heap,
+                           content_ty: ty::t) {
         /*!
          * Schedules a call to `free(val)`. Note that this is a shallow
          * operation.
          */
 
-        let drop = box FreeValue { ptr: val, heap: heap };
+        let drop = box FreeValue { ptr: val, heap: heap, content_ty: content_ty };
 
         debug!("schedule_free_value({:?}, val={}, heap={:?})",
                cleanup_scope,
@@ -847,6 +848,7 @@ pub enum Heap {
 pub struct FreeValue {
     ptr: ValueRef,
     heap: Heap,
+    content_ty: ty::t
 }
 
 impl Cleanup for FreeValue {
@@ -860,7 +862,7 @@ impl Cleanup for FreeValue {
                 glue::trans_free(bcx, self.ptr)
             }
             HeapExchange => {
-                glue::trans_exchange_free(bcx, self.ptr)
+                glue::trans_exchange_free_ty(bcx, self.ptr, self.content_ty)
             }
         }
     }
@@ -931,7 +933,8 @@ pub trait CleanupMethods<'a> {
     fn schedule_free_value(&self,
                            cleanup_scope: ScopeId,
                            val: ValueRef,
-                           heap: Heap);
+                           heap: Heap,
+                           content_ty: ty::t);
     fn schedule_clean(&self,
                       cleanup_scope: ScopeId,
                       cleanup: Box<Cleanup>);

src/librustc/middle/trans/expr.rs

@@ -1183,7 +1183,7 @@ fn trans_uniq_expr<'a>(bcx: &'a Block<'a>,
     } else {
         let custom_cleanup_scope = fcx.push_custom_cleanup_scope();
         fcx.schedule_free_value(cleanup::CustomScope(custom_cleanup_scope),
-                                val, cleanup::HeapExchange);
+                                val, cleanup::HeapExchange, contents_ty);
         let bcx = trans_into(bcx, contents, SaveIn(val));
         fcx.pop_custom_cleanup_scope(custom_cleanup_scope);
         bcx
@@ -1205,7 +1205,7 @@ fn trans_managed_expr<'a>(bcx: &'a Block<'a>,
 
     let custom_cleanup_scope = fcx.push_custom_cleanup_scope();
     fcx.schedule_free_value(cleanup::CustomScope(custom_cleanup_scope),
-                            bx, cleanup::HeapManaged);
+                            bx, cleanup::HeapManaged, contents_ty);
     let bcx = trans_into(bcx, contents, SaveIn(body));
     fcx.pop_custom_cleanup_scope(custom_cleanup_scope);
     immediate_rvalue_bcx(bcx, bx, box_ty).to_expr_datumblock()
@@ -1789,13 +1789,14 @@ fn deref_once<'a>(bcx: &'a Block<'a>,
                 let scope = cleanup::temporary_scope(bcx.tcx(), expr.id);
                 let ptr = Load(bcx, datum.val);
                 if !type_is_zero_size(bcx.ccx(), content_ty) {
-                    bcx.fcx.schedule_free_value(scope, ptr, cleanup::HeapExchange);
+                    bcx.fcx.schedule_free_value(scope, ptr, cleanup::HeapExchange, content_ty);
                 }
             }
             RvalueExpr(Rvalue { mode: ByValue }) => {
                 let scope = cleanup::temporary_scope(bcx.tcx(), expr.id);
                 if !type_is_zero_size(bcx.ccx(), content_ty) {
-                    bcx.fcx.schedule_free_value(scope, datum.val, cleanup::HeapExchange);
+                    bcx.fcx.schedule_free_value(scope, datum.val, cleanup::HeapExchange,
+                                                content_ty);
                 }
             }
             LvalueExpr => { }

src/librustc/middle/trans/glue.rs

@@ -50,15 +50,30 @@ pub fn trans_free<'a>(cx: &'a Block<'a>, v: ValueRef) -> &'a Block<'a> {
         Some(expr::Ignore)).bcx
 }
 
-pub fn trans_exchange_free<'a>(cx: &'a Block<'a>, v: ValueRef)
-                           -> &'a Block<'a> {
+fn trans_exchange_free<'a>(cx: &'a Block<'a>, v: ValueRef, size: u64,
+                               align: u64) -> &'a Block<'a> {
     let _icx = push_ctxt("trans_exchange_free");
+    let ccx = cx.ccx();
     callee::trans_lang_call(cx,
         langcall(cx, None, "", ExchangeFreeFnLangItem),
-        [PointerCast(cx, v, Type::i8p(cx.ccx()))],
+        [PointerCast(cx, v, Type::i8p(ccx)), C_uint(ccx, size as uint), C_uint(ccx, align as uint)],
         Some(expr::Ignore)).bcx
 }
 
+pub fn trans_exchange_free_ty<'a>(bcx: &'a Block<'a>, ptr: ValueRef,
+                                  content_ty: ty::t) -> &'a Block<'a> {
+    let sizing_type = sizing_type_of(bcx.ccx(), content_ty);
+    let content_size = llsize_of_alloc(bcx.ccx(), sizing_type);
+
+    // `Box<ZeroSizeType>` does not allocate.
+    if content_size != 0 {
+        let content_align = llalign_of_min(bcx.ccx(), sizing_type);
+        trans_exchange_free(bcx, ptr, content_size, content_align)
+    } else {
+        bcx
+    }
+}
+
 pub fn take_ty<'a>(bcx: &'a Block<'a>, v: ValueRef, t: ty::t)
                -> &'a Block<'a> {
     // NB: v is an *alias* of type t here, not a direct value.
@@ -87,17 +102,15 @@ fn get_drop_glue_type(ccx: &CrateContext, t: ty::t) -> ty::t {
                 ty::ty_vec(_, None) | ty::ty_str => t,
                 _ => {
                     let llty = sizing_type_of(ccx, typ);
-                    // Unique boxes do not allocate for zero-size types. The standard
-                    // library may assume that `free` is never called on the pointer
-                    // returned for `Box<ZeroSizeType>`.
+                    // `Box<ZeroSizeType>` does not allocate.
                     if llsize_of_alloc(ccx, llty) == 0 {
                         ty::mk_i8()
                     } else {
                         ty::mk_uniq(tcx, ty::mk_i8())
                     }
-                        }
-                    }
                 }
+            }
+        }
         _ => t
     }
 }
@@ -285,20 +298,22 @@ fn make_drop_glue<'a>(bcx: &'a Block<'a>, v0: ValueRef, t: ty::t) -> &'a Block<'
                 ty::ty_vec(mt, None) => {
                     with_cond(bcx, not_null, |bcx| {
                         let bcx = tvec::make_drop_glue_unboxed(bcx, llbox, mt.ty);
-                        trans_exchange_free(bcx, llbox)
+                        // FIXME: #13994: the old `Box<[T]>` will not support sized deallocation
+                        trans_exchange_free(bcx, llbox, 0, 8)
                     })
                 }
                 ty::ty_str => {
                     with_cond(bcx, not_null, |bcx| {
                         let unit_ty = ty::sequence_element_type(bcx.tcx(), t);
                         let bcx = tvec::make_drop_glue_unboxed(bcx, llbox, unit_ty);
-                        trans_exchange_free(bcx, llbox)
+                        // FIXME: #13994: the old `Box<str>` will not support sized deallocation
+                        trans_exchange_free(bcx, llbox, 0, 8)
                     })
                 }
                 _ => {
                     with_cond(bcx, not_null, |bcx| {
                         let bcx = drop_ty(bcx, llbox, content_ty);
-                        trans_exchange_free(bcx, llbox)
+                        trans_exchange_free_ty(bcx, llbox, content_ty)
                     })
                 }
             }
@@ -340,7 +355,8 @@ fn make_drop_glue<'a>(bcx: &'a Block<'a>, v0: ValueRef, t: ty::t) -> &'a Block<'
                 Call(bcx, dtor, [PointerCast(bcx, cdata, Type::i8p(bcx.ccx()))], []);
 
                 // Free the environment itself
-                trans_exchange_free(bcx, env)
+                // FIXME: #13994: pass align and size here
+                trans_exchange_free(bcx, env, 0, 8)
             })
         }
         _ => {

src/librustc/middle/trans/tvec.rs

@@ -287,8 +287,11 @@ pub fn trans_uniq_vstore<'a>(bcx: &'a Block<'a>,
     // Create a temporary scope lest execution should fail while
     // constructing the vector.
     let temp_scope = fcx.push_custom_cleanup_scope();
+
+    // FIXME: #13994: the old `Box<[T]> will not support sized deallocation, this is a placeholder
+    let content_ty = vt.unit_ty;
     fcx.schedule_free_value(cleanup::CustomScope(temp_scope),
-                            val, cleanup::HeapExchange);
+                            val, cleanup::HeapExchange, content_ty);
 
     let dataptr = get_dataptr(bcx, val);