Pull building the environment for for_each into a seperate function.

Author: msullivan

src/comp/middle/trans.rs

@@ -4196,45 +4196,17 @@ fn collect_upvars(&@block_ctxt cx, &ast::block bloc,
     ret result;
 }
 
-fn trans_for_each(&@block_ctxt cx, &@ast::local local, &@ast::expr seq,
-                  &ast::block body) -> result {
-    /*
-     * The translation is a little .. complex here. Code like:
-     *
-     *    let ty1 p = ...;
-     *
-     *    let ty1 q = ...;
-     *
-     *    foreach (ty v in foo(a,b)) { body(p,q,v) }
-     *
-     *
-     * Turns into a something like so (C/Rust mishmash):
-     *
-     *    type env = { *ty1 p, *ty2 q, ... };
-     *
-     *    let env e = { &p, &q, ... };
-     *
-     *    fn foreach123_body(env* e, ty v) { body(*(e->p),*(e->q),v) }
-     *
-     *    foo([foreach123_body, env*], a, b);
-     *
-     */
-
-    // Step 1: walk body and figure out which references it makes
-    // escape. This could be determined upstream, and probably ought
-    // to be so, eventualy.
-
-    auto lcx = cx.fcx.lcx;
-    // FIXME: possibly support alias-mode here?
-
-    auto decl_ty = node_id_type(lcx.ccx, local.node.id);
-    auto decl_id = local.node.id;
-    auto upvars = collect_upvars(cx, body, decl_id);
+// Given a block context and a list of upvars, construct a closure that
+// contains pointers to all of the upvars and all of the tydescs in
+// scope. Return the ValueRef and TypeRef corresponding to the closure. 
+fn build_environment(&@block_ctxt cx, &vec[ast::node_id] upvars) ->
+    tup(ValueRef, TypeRef)
+{
     auto upvar_count = vec::len(upvars);
     auto llbindingsptr;
+
     if (upvar_count > 0u) {
         // Gather up the upvars.
-
         let vec[ValueRef] llbindings = [];
         let vec[TypeRef] llbindingtys = [];
         for (ast::node_id nid in upvars) {
@@ -4253,8 +4225,8 @@ fn trans_for_each(&@block_ctxt cx, &@ast::local local, &@ast::expr seq,
             llbindings += [llbinding];
             llbindingtys += [val_ty(llbinding)];
         }
-        // Create an array of bindings and copy in aliases to the upvars.
 
+        // Create an array of bindings and copy in aliases to the upvars.
         llbindingsptr = alloca(cx, T_struct(llbindingtys));
         auto i = 0u;
         while (i < upvar_count) {
@@ -4265,23 +4237,22 @@ fn trans_for_each(&@block_ctxt cx, &@ast::local local, &@ast::expr seq,
         }
     } else {
         // Null bindings.
-
         llbindingsptr = C_null(T_ptr(T_i8()));
     }
-    // Create an environment and populate it with the bindings.
 
+    // Create an environment and populate it with the bindings.
     auto tydesc_count = vec::len[ValueRef](cx.fcx.lltydescs);
     auto llenvptrty =
-        T_closure_ptr(lcx.ccx.tn, T_ptr(T_nil()), val_ty(llbindingsptr),
-                      tydesc_count);
+        T_closure_ptr(cx.fcx.lcx.ccx.tn, T_ptr(T_nil()),
+                      val_ty(llbindingsptr), tydesc_count);
     auto llenvptr = alloca(cx, llvm::LLVMGetElementType(llenvptrty));
     auto llbindingsptrptr =
         cx.build.GEP(llenvptr,
                      [C_int(0), C_int(abi::box_rc_field_body), C_int(2)]);
     cx.build.Store(llbindingsptr, llbindingsptrptr);
+
     // Copy in our type descriptors, in case the iterator body needs to refer
     // to them.
-
     auto lltydescsptr =
         cx.build.GEP(llenvptr,
                      [C_int(0), C_int(abi::box_rc_field_body),
@@ -4293,16 +4264,58 @@ fn trans_for_each(&@block_ctxt cx, &@ast::local local, &@ast::expr seq,
         cx.build.Store(cx.fcx.lltydescs.(i), lltydescptr);
         i += 1u;
     }
-    // Step 2: Declare foreach body function.
 
+    ret tup(llenvptr, llenvptrty);
+}
+
+fn trans_for_each(&@block_ctxt cx, &@ast::local local, &@ast::expr seq,
+                  &ast::block body) -> result {
+    /*
+     * The translation is a little .. complex here. Code like:
+     *
+     *    let ty1 p = ...;
+     *
+     *    let ty1 q = ...;
+     *
+     *    foreach (ty v in foo(a,b)) { body(p,q,v) }
+     *
+     *
+     * Turns into a something like so (C/Rust mishmash):
+     *
+     *    type env = { *ty1 p, *ty2 q, ... };
+     *
+     *    let env e = { &p, &q, ... };
+     *
+     *    fn foreach123_body(env* e, ty v) { body(*(e->p),*(e->q),v) }
+     *
+     *    foo([foreach123_body, env*], a, b);
+     *
+     */
+
+    // Step 1: walk body and figure out which references it makes
+    // escape. This could be determined upstream, and probably ought
+    // to be so, eventualy.
+    auto lcx = cx.fcx.lcx;
+
+    // FIXME: possibly support alias-mode here?
+    auto decl_ty = node_id_type(lcx.ccx, local.node.id);
+    auto decl_id = local.node.id;
+    auto upvars = collect_upvars(cx, body, decl_id);
+    auto upvar_count = vec::len(upvars);
+
+    auto environment_data = build_environment(cx, upvars);
+    auto llenvptr = environment_data._0;
+    auto llenvptrty = environment_data._1;
+
+    // Step 2: Declare foreach body function.
     let str s =
         mangle_internal_name_by_path_and_seq(lcx.ccx, lcx.path, "foreach");
+
     // The 'env' arg entering the body function is a fake env member (as in
     // the env-part of the normal rust calling convention) that actually
     // points to a stack allocated env in this frame. We bundle that env
     // pointer along with the foreach-body-fn pointer into a 'normal' fn pair
     // and pass it in as a first class fn-arg to the iterator.
-
     auto iter_body_llty =
         type_of_fn_full(lcx.ccx, cx.sp, ast::proto_fn, none[TypeRef],
                         [rec(mode=ty::mo_alias(false), ty=decl_ty)],
@@ -4311,8 +4324,8 @@ fn trans_for_each(&@block_ctxt cx, &@ast::local local, &@ast::expr seq,
         decl_internal_fastcall_fn(lcx.ccx.llmod, s, iter_body_llty);
     auto fcx = new_fn_ctxt(lcx, cx.sp, lliterbody);
     auto copy_args_bcx = new_raw_block_ctxt(fcx, fcx.llcopyargs);
-    // Populate the upvars from the environment.
 
+    // Populate the upvars from the environment.
     auto llremoteenvptr =
         copy_args_bcx.build.PointerCast(fcx.llenv, llenvptrty);
     auto llremotebindingsptrptr =
@@ -4321,7 +4334,7 @@ fn trans_for_each(&@block_ctxt cx, &@ast::local local, &@ast::expr seq,
                                  C_int(abi::closure_elt_bindings)]);
     auto llremotebindingsptr =
         copy_args_bcx.build.Load(llremotebindingsptrptr);
-    i = 0u;
+    auto i = 0u;
     while (i < upvar_count) {
         auto upvar_id = upvars.(i);
         auto llupvarptrptr =
@@ -4331,12 +4344,13 @@ fn trans_for_each(&@block_ctxt cx, &@ast::local local, &@ast::expr seq,
         fcx.llupvars.insert(upvar_id, llupvarptr);
         i += 1u;
     }
-    // Populate the type parameters from the environment.
 
+    // Populate the type parameters from the environment.
     auto llremotetydescsptr =
         copy_args_bcx.build.GEP(llremoteenvptr,
                                 [C_int(0), C_int(abi::box_rc_field_body),
                                  C_int(abi::closure_elt_ty_params)]);
+    auto tydesc_count = vec::len[ValueRef](cx.fcx.lltydescs);
     i = 0u;
     while (i < tydesc_count) {
         auto llremotetydescptr =
@@ -4346,8 +4360,8 @@ fn trans_for_each(&@block_ctxt cx, &@ast::local local, &@ast::expr seq,
         fcx.lltydescs += [llremotetydesc];
         i += 1u;
     }
-    // Add an upvar for the loop variable alias.
 
+    // Add an upvar for the loop variable alias.
     fcx.llupvars.insert(decl_id, llvm::LLVMGetParam(fcx.llfn, 3u));
     auto bcx = new_top_block_ctxt(fcx);
     auto lltop = bcx.llbb;