auto merge of #15439 : dotdash/rust/remove_entry_bcx, r=pcwalton

We no longer need to refer to the entry block from arbitrary places, so
we can drop it from FunctionContext.

Author: bors

src/librustc/middle/trans/base.rs

@@ -1112,8 +1112,7 @@ pub fn make_return_pointer(fcx: &FunctionContext, output_type: ty::t)
             llvm::LLVMGetParam(fcx.llfn, 0)
         } else {
             let lloutputtype = type_of::type_of(fcx.ccx, output_type);
-            let bcx = fcx.entry_bcx.borrow().clone().unwrap();
-            Alloca(bcx, lloutputtype, "__make_return_pointer")
+            AllocaFcx(fcx, lloutputtype, "__make_return_pointer")
         }
     }
 }
@@ -1154,7 +1153,6 @@ pub fn new_fn_ctxt<'a>(ccx: &'a CrateContext,
           llfn: llfndecl,
           llenv: None,
           llretptr: Cell::new(None),
-          entry_bcx: RefCell::new(None),
           alloca_insert_pt: Cell::new(None),
           llreturn: Cell::new(None),
           personality: Cell::new(None),
@@ -1184,11 +1182,9 @@ pub fn new_fn_ctxt<'a>(ccx: &'a CrateContext,
 /// and allocating space for the return pointer.
 pub fn init_function<'a>(fcx: &'a FunctionContext<'a>,
                          skip_retptr: bool,
-                         output_type: ty::t) {
+                         output_type: ty::t) -> &'a Block<'a> {
     let entry_bcx = fcx.new_temp_block("entry-block");
 
-    *fcx.entry_bcx.borrow_mut() = Some(entry_bcx);
-
     // Use a dummy instruction as the insertion point for all allocas.
     // This is later removed in FunctionContext::cleanup.
     fcx.alloca_insert_pt.set(Some(unsafe {
@@ -1210,6 +1206,8 @@ pub fn init_function<'a>(fcx: &'a FunctionContext<'a>,
             fcx.llretptr.set(Some(make_return_pointer(fcx, substd_output_type)));
         }
     }
+
+    entry_bcx
 }
 
 // NB: must keep 4 fns in sync:
@@ -1364,15 +1362,11 @@ pub fn trans_closure(ccx: &CrateContext,
                           param_substs,
                           Some(body.span),
                           &arena);
-    init_function(&fcx, false, output_type);
+    let mut bcx = init_function(&fcx, false, output_type);
 
     // cleanup scope for the incoming arguments
     let arg_scope = fcx.push_custom_cleanup_scope();
 
-    // Create the first basic block in the function and keep a handle on it to
-    //  pass to finish_fn later.
-    let bcx_top = fcx.entry_bcx.borrow().clone().unwrap();
-    let mut bcx = bcx_top;
     let block_ty = node_id_type(bcx, body.id);
 
     // Set up arguments to the function.
@@ -1499,14 +1493,12 @@ fn trans_enum_variant_or_tuple_like_struct(ccx: &CrateContext,
     let arena = TypedArena::new();
     let fcx = new_fn_ctxt(ccx, llfndecl, ctor_id, false, result_ty,
                           param_substs, None, &arena);
-    init_function(&fcx, false, result_ty);
+    let bcx = init_function(&fcx, false, result_ty);
 
     let arg_tys = ty::ty_fn_args(ctor_ty);
 
     let arg_datums = create_datums_for_fn_args(&fcx, arg_tys.as_slice());
 
-    let bcx = fcx.entry_bcx.borrow().clone().unwrap();
-
     if !type_is_zero_size(fcx.ccx, result_ty) {
         let repr = adt::represent_type(ccx, result_ty);
         adt::trans_start_init(bcx, &*repr, fcx.llretptr.get().unwrap(), disr);

src/librustc/middle/trans/callee.rs

@@ -277,10 +277,9 @@ pub fn trans_unboxing_shim(bcx: &Block,
                           &empty_param_substs,
                           None,
                           &block_arena);
-    init_function(&fcx, false, return_type);
+    let mut bcx = init_function(&fcx, false, return_type);
 
     // Create the substituted versions of the self type.
-    let mut bcx = fcx.entry_bcx.borrow().clone().unwrap();
     let arg_scope = fcx.push_custom_cleanup_scope();
     let arg_scope_id = cleanup::CustomScope(arg_scope);
     let boxed_arg_types = ty::ty_fn_args(boxed_function_type);

src/librustc/middle/trans/closure.rs

@@ -424,8 +424,7 @@ pub fn get_wrapper_for_bare_fn(ccx: &CrateContext,
     let empty_param_substs = param_substs::empty();
     let fcx = new_fn_ctxt(ccx, llfn, -1, true, f.sig.output,
                           &empty_param_substs, None, &arena);
-    init_function(&fcx, true, f.sig.output);
-    let bcx = fcx.entry_bcx.borrow().clone().unwrap();
+    let bcx = init_function(&fcx, true, f.sig.output);
 
     let args = create_datums_for_fn_args(&fcx,
                                          ty::ty_fn_args(closure_ty)

src/librustc/middle/trans/common.rs

@@ -239,8 +239,6 @@ pub struct FunctionContext<'a> {
     // always be Some.
     pub llretptr: Cell<Option<ValueRef>>,
 
-    pub entry_bcx: RefCell<Option<&'a Block<'a>>>,
-
     // These pub elements: "hoisted basic blocks" containing
     // administrative activities that have to happen in only one place in
     // the function, due to LLVM's quirks.
@@ -322,8 +320,6 @@ impl<'a> FunctionContext<'a> {
                                                      .get()
                                                      .unwrap());
         }
-        // Remove the cycle between fcx and bcx, so memory can be freed
-        *self.entry_bcx.borrow_mut() = None;
     }
 
     pub fn get_llreturn(&self) -> BasicBlockRef {

src/librustc/middle/trans/glue.rs

@@ -490,7 +490,7 @@ fn make_generic_glue(ccx: &CrateContext,
     let fcx = new_fn_ctxt(ccx, llfn, -1, false, ty::mk_nil(),
                           &empty_param_substs, None, &arena);
 
-    init_function(&fcx, false, ty::mk_nil());
+    let bcx = init_function(&fcx, false, ty::mk_nil());
 
     lib::llvm::SetLinkage(llfn, lib::llvm::InternalLinkage);
     ccx.stats.n_glues_created.set(ccx.stats.n_glues_created.get() + 1u);
@@ -502,7 +502,6 @@ fn make_generic_glue(ccx: &CrateContext,
     // llfn is expected be declared to take a parameter of the appropriate
     // type, so we don't need to explicitly cast the function parameter.
 
-    let bcx = fcx.entry_bcx.borrow().clone().unwrap();
     let llrawptr0 = unsafe { llvm::LLVMGetParam(llfn, fcx.arg_pos(0) as c_uint) };
     let bcx = helper(bcx, llrawptr0, t);
     finish_fn(&fcx, bcx);

src/librustc/middle/trans/intrinsic.rs

@@ -188,11 +188,10 @@ pub fn trans_intrinsic(ccx: &CrateContext,
     let arena = TypedArena::new();
     let fcx = new_fn_ctxt(ccx, decl, item.id, false, output_type,
                           substs, Some(item.span), &arena);
-    init_function(&fcx, true, output_type);
+    let mut bcx = init_function(&fcx, true, output_type);
 
     set_always_inline(fcx.llfn);
 
-    let mut bcx = fcx.entry_bcx.borrow().clone().unwrap();
     let first_real_arg = fcx.arg_pos(0u);
 
     let name = token::get_ident(item.ident);

src/librustc/middle/trans/reflect.rs

@@ -313,7 +313,7 @@ impl<'a, 'b> Reflector<'a, 'b> {
                 let fcx = new_fn_ctxt(ccx, llfdecl, -1, false,
                                       ty::mk_u64(), &empty_param_substs,
                                       None, &arena);
-                init_function(&fcx, false, ty::mk_u64());
+                let bcx = init_function(&fcx, false, ty::mk_u64());
 
                 let arg = unsafe {
                     //
@@ -323,7 +323,6 @@ impl<'a, 'b> Reflector<'a, 'b> {
                     //
                     llvm::LLVMGetParam(llfdecl, fcx.arg_pos(0u) as c_uint)
                 };
-                let bcx = fcx.entry_bcx.borrow().clone().unwrap();
                 let arg = BitCast(bcx, arg, llptrty);
                 let ret = adt::trans_get_discr(bcx, &*repr, arg, Some(Type::i64(ccx)));
                 Store(bcx, ret, fcx.llretptr.get().unwrap());