Ensure hole checks take place in switch statement scopes

src/full-codegen/arm/full-codegen-arm.cc

Index: src/full-codegen/arm/full-codegen-arm.cc
diff --git a/src/full-codegen/arm/full-codegen-arm.cc b/src/full-codegen/arm/full-codegen-arm.cc
index 891888d232def562938c690516bb0c84a7326abe..aa728ed99c55f5bef01b22095c748bd171b13806 100644
--- a/src/full-codegen/arm/full-codegen-arm.cc
+++ b/src/full-codegen/arm/full-codegen-arm.cc
@@ -1454,67 +1454,26 @@ void FullCodeGenerator::EmitVariableLoad(VariableProxy* proxy,
       DCHECK_EQ(NOT_INSIDE_TYPEOF, typeof_mode);
       Comment cmnt(masm_, var->IsContextSlot() ? "[ Context variable"
                                                : "[ Stack variable");
-      if (var->binding_needs_init()) {
-        // var->scope() may be NULL when the proxy is located in eval code and
-        // refers to a potential outside binding. Currently those bindings are
-        // always looked up dynamically, i.e. in that case
-        //     var->location() == LOOKUP.
-        // always holds.
-        DCHECK(var->scope() != NULL);
-
-        // Check if the binding really needs an initialization check. The check
-        // can be skipped in the following situation: we have a LET or CONST
-        // binding in harmony mode, both the Variable and the VariableProxy have
-        // the same declaration scope (i.e. they are both in global code, in the
-        // same function or in the same eval code) and the VariableProxy is in
-        // the source physically located after the initializer of the variable.
-        //
-        // We cannot skip any initialization checks for CONST in non-harmony
-        // mode because const variables may be declared but never initialized:
-        //   if (false) { const x; }; var y = x;
-        //
-        // The condition on the declaration scopes is a conservative check for
-        // nested functions that access a binding and are called before the
-        // binding is initialized:
-        //   function() { f(); let x = 1; function f() { x = 2; } }
-        //
-        bool skip_init_check;
-        if (var->scope()->DeclarationScope() != scope()->DeclarationScope()) {
-          skip_init_check = false;
-        } else if (var->is_this()) {
-          CHECK(info_->has_literal() &&
-                (info_->literal()->kind() & kSubclassConstructor) != 0);
-          // TODO(dslomov): implement 'this' hole check elimination.
-          skip_init_check = false;
+      if (NeedsHoleCheck(proxy)) {
+        // Let and const need a read barrier.
+        GetVar(r0, var);
+        __ CompareRoot(r0, Heap::kTheHoleValueRootIndex);
+        if (var->mode() == LET || var->mode() == CONST) {
+          // Throw a reference error when using an uninitialized let/const
+          // binding in harmony mode.
+          Label done;
+          __ b(ne, &done);
+          __ mov(r0, Operand(var->name()));
+          __ push(r0);
+          __ CallRuntime(Runtime::kThrowReferenceError, 1);
+          __ bind(&done);
         } else {
-          // Check that we always have valid source position.
-          DCHECK(var->initializer_position() != RelocInfo::kNoPosition);
-          DCHECK(proxy->position() != RelocInfo::kNoPosition);
-          skip_init_check = var->mode() != CONST_LEGACY &&
-              var->initializer_position() < proxy->position();
-        }
-
-        if (!skip_init_check) {
-          // Let and const need a read barrier.
-          GetVar(r0, var);
-          __ CompareRoot(r0, Heap::kTheHoleValueRootIndex);
-          if (var->mode() == LET || var->mode() == CONST) {
-            // Throw a reference error when using an uninitialized let/const
-            // binding in harmony mode.
-            Label done;
-            __ b(ne, &done);
-            __ mov(r0, Operand(var->name()));
-            __ push(r0);
-            __ CallRuntime(Runtime::kThrowReferenceError, 1);
-            __ bind(&done);
-          } else {
-            // Uninitalized const bindings outside of harmony mode are unholed.
-            DCHECK(var->mode() == CONST_LEGACY);
-            __ LoadRoot(r0, Heap::kUndefinedValueRootIndex, eq);
-          }
-          context()->Plug(r0);
-          break;
+          // Uninitalized const bindings outside of harmony mode are unholed.

[adamk, 2015/08/24 22:15:00]

Typo (pre-existing, but might as well fix now): s/Uninitalized/Uninitialized/

That'll take you over 80 chars, but you could change this to:

// Uninitialized legacy const bindings are unholed.

Same goes for all other full codegen files.

[Dan Ehrenberg, 2015/08/25 01:48:13]

Fixed

+          DCHECK(var->mode() == CONST_LEGACY);
+          __ LoadRoot(r0, Heap::kUndefinedValueRootIndex, eq);
         }
+        context()->Plug(r0);
+        break;
       }
       context()->Plug(var);
       break;