[ignition] Eliminate hole checks where statically possible for loads and stores

src/full-codegen/full-codegen.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/full-codegen/full-codegen.h"
 
 #include "src/ast/ast-numbering.h"
 #include "src/ast/ast.h"
 #include "src/ast/prettyprinter.h"
 #include "src/ast/scopes.h"
@@ skipping 1964 matching lines @@
     codegen_->LoadContextField(codegen_->context_register(),
                                Context::PREVIOUS_INDEX);
     // Update local stack frame context field.
     codegen_->StoreToFrameField(StandardFrameConstants::kContextOffset,
                                 codegen_->context_register());
   }
   codegen_->PrepareForBailoutForId(exit_id_, BailoutState::NO_REGISTERS);
   codegen_->scope_ = saved_scope_;
 }
 
-
-bool FullCodeGenerator::NeedsHoleCheckForLoad(VariableProxy* proxy) {
-  Variable* var = proxy->var();
-
-  if (!var->binding_needs_init()) {
-    return false;
-  }
-
-  // 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);
-  DCHECK(var->location() == VariableLocation::PARAMETER ||
-         var->location() == VariableLocation::LOCAL ||
-         var->location() == VariableLocation::CONTEXT);
-
-  // 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), the VariableProxy is in
-  // the source physically located after the initializer of the variable,
-  // and that the initializer cannot be skipped due to a nonlinear scope.
-  //
-  // 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; } }
-  //
-  // The check cannot be skipped on non-linear scopes, namely switch
-  // scopes, to ensure tests are done in cases like the following:
-  //   switch (1) { case 0: let x = 2; case 1: f(x); }
-  // The scope of the variable needs to be checked, in case the use is
-  // in a sub-block which may be linear.
-  if (var->scope()->GetDeclarationScope() != scope()->GetDeclarationScope()) {
-    return true;
-  }
-
-  if (var->is_this()) {
-    DCHECK(literal() != nullptr &&
-           (literal()->kind() & kSubclassConstructor) != 0);
-    // TODO(littledan): implement 'this' hole check elimination.
-    return true;
-  }
-
-  // Check that we always have valid source position.
-  DCHECK(var->initializer_position() != kNoSourcePosition);
-  DCHECK(proxy->position() != kNoSourcePosition);
-
-  return var->scope()->is_nonlinear() ||
-         var->initializer_position() >= proxy->position();
-}
-
 Handle<Script> FullCodeGenerator::script() { return info_->script(); }
 
 LanguageMode FullCodeGenerator::language_mode() {
   return scope()->language_mode();
 }
 
 bool FullCodeGenerator::has_simple_parameters() {
   return info_->has_simple_parameters();
 }
 
 FunctionLiteral* FullCodeGenerator::literal() const { return info_->literal(); }
 
 #undef __
 
 
 }  // namespace internal
 }  // namespace v8