Simplify translation of conditionals in the flow graph builder.

runtime/vm/flow_graph_builder.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/flow_graph_builder.h"
 
 #include "vm/ast_printer.h"
 #include "vm/flags.h"
 #include "vm/intermediate_language.h"
 #include "vm/longjump.h"
@@ skipping 35 matching lines @@
                               const EffectGraphVisitor& false_fragment) {
   // We have: a test graph fragment with zero, one, or two available exits;
   // and a pair of effect graph fragments with zero or one available exits.
   // We want to append the branch and (if necessary) a join node to this
   // graph fragment.
   ASSERT(is_open());
 
   // 1. Connect the test to this graph.
   Append(test_fragment);
 
-  // 2. Connect the true and false bodies to the test if they are reachable,
-  // and if so record their exits (if any).
+  // 2. Connect the true and false bodies to the test and record their exits
+  // (if any).
   Instruction* true_exit = NULL;
   Instruction* false_exit = NULL;
-  if (test_fragment.can_be_true()) {
-    TargetEntryInstr* true_entry = new TargetEntryInstr();
-    *test_fragment.true_successor_address() = true_entry;
-    true_entry->SetSuccessor(true_fragment.entry());
-    true_exit = true_fragment.is_empty() ? true_entry : true_fragment.exit();
+  TargetEntryInstr* true_entry = new TargetEntryInstr();
+  *test_fragment.true_successor_address() = true_entry;
+  true_entry->SetSuccessor(true_fragment.entry());
+  true_exit = true_fragment.is_empty() ? true_entry : true_fragment.exit();
 
-    TargetEntryInstr* false_entry = new TargetEntryInstr();
-    *test_fragment.false_successor_address() = false_entry;
-    false_entry->SetSuccessor(false_fragment.entry());
-    false_exit =
-        false_fragment.is_empty() ? false_entry : false_fragment.exit();
-  }
+  TargetEntryInstr* false_entry = new TargetEntryInstr();
+  *test_fragment.false_successor_address() = false_entry;
+  false_entry->SetSuccessor(false_fragment.entry());
+  false_exit = false_fragment.is_empty() ? false_entry : false_fragment.exit();
 
   // 3. Add a join or select one (or neither) of the arms as exit.
   if (true_exit == NULL) {
     exit_ = false_exit;  // May be NULL.
   } else if (false_exit == NULL) {
     exit_ = true_exit;
   } else {
     exit_ = new JoinEntryInstr();
     true_exit->SetSuccessor(exit_);
     false_exit->SetSuccessor(exit_);
   }
 }
 
 
 void EffectGraphVisitor::TieLoop(const TestGraphVisitor& test_fragment,
                                  const EffectGraphVisitor& body_fragment) {
   // We have: a test graph fragment with zero, one, or two available exits;
   // and an effect graph fragment with zero or one available exits.  We want
   // to append the 'while loop' consisting of the test graph fragment as
   // condition and the effect graph fragment as body.
   ASSERT(is_open());
 
   // 1. Connect the body to the test if it is reachable, and if so record
   // its exit (if any).
   Instruction* body_exit = NULL;
-  if (test_fragment.can_be_true()) {
-    TargetEntryInstr* body_entry = new TargetEntryInstr();
-    *test_fragment.true_successor_address() = body_entry;
-    body_entry->SetSuccessor(body_fragment.entry());
-    body_exit = body_fragment.is_empty() ? body_entry : body_fragment.exit();
-  }
+  TargetEntryInstr* body_entry = new TargetEntryInstr();
+  *test_fragment.true_successor_address() = body_entry;
+  body_entry->SetSuccessor(body_fragment.entry());
+  body_exit = body_fragment.is_empty() ? body_entry : body_fragment.exit();
 
   // 2. Connect the test to this graph, including the body if reachable and
   // using a fresh join node if the body is reachable and has an open exit.
   if (body_exit == NULL) {
     Append(test_fragment);
   } else {
     JoinEntryInstr* join = new JoinEntryInstr();
     AddInstruction(join);
     join->SetSuccessor(test_fragment.entry());
     body_exit->SetSuccessor(join);
   }
 
-  // 3. Set the exit to the graph to be empty or a fresh target node
-  // depending on whether the false branch of the test is reachable.
-  if (test_fragment.can_be_false()) {
-    exit_ = *test_fragment.false_successor_address() = new TargetEntryInstr();
-  } else {
-    exit_ = NULL;
-  }
+  // 3. Set the exit to the graph to be the false successor of the test, a
+  // fresh target node
+  exit_ = *test_fragment.false_successor_address() = new TargetEntryInstr();
 }
 
 
 void TestGraphVisitor::ReturnValue(Value* value) {
   BranchInstr* branch = new BranchInstr(value);
   AddInstruction(branch);
   CloseFragment();
   true_successor_address_ = branch->true_successor_address();
   false_successor_address_ = branch->false_successor_address();
 }
@@ skipping 492 matching lines @@
       new InstanceCallComp(node->store_id(), node->token_index(), store_name,
                            arguments, Array::ZoneHandle(), 1);
   AddInstruction(new DoInstr(store));
   ReturnValue(new TempVal(AllocateTempIndex()));
 }
 
 
 void EffectGraphVisitor::VisitConditionalExprNode(ConditionalExprNode* node) {
   TestGraphVisitor for_test(owner(), temp_index());
   node->condition()->Visit(&for_test);
-  ASSERT(for_test.can_be_true() && for_test.can_be_false());
 
   // Translate the subexpressions for their effects.
   EffectGraphVisitor for_true(owner(), temp_index());
   node->true_expr()->Visit(&for_true);
   EffectGraphVisitor for_false(owner(), temp_index());
   node->false_expr()->Visit(&for_false);
 
   Join(for_test, for_true, for_false);
 }
 
 
 void ValueGraphVisitor::VisitConditionalExprNode(ConditionalExprNode* node) {
   TestGraphVisitor for_test(owner(), temp_index());
   node->condition()->Visit(&for_test);
-  ASSERT(for_test.can_be_true() && for_test.can_be_false());
 
   // Ensure that the value of the true/false subexpressions are named with
   // the same temporary name.
   ValueGraphVisitor for_true(owner(), temp_index());
   node->true_expr()->Visit(&for_true);
   ASSERT(for_true.is_open());
   if (for_true.value()->IsTemp()) {
     ASSERT(for_true.value()->AsTemp()->index() == temp_index());
   } else {
     for_true.AddInstruction(new BindInstr(temp_index(), for_true.value()));
@@ skipping 16 matching lines @@
 // <Statement> ::= If { condition: <Expression>
 //                      true_branch: <Sequence>
 //                      false_branch: <Sequence> }
 void EffectGraphVisitor::VisitIfNode(IfNode* node) {
   TestGraphVisitor for_test(owner(), temp_index());
   node->condition()->Visit(&for_test);
 
   EffectGraphVisitor for_true(owner(), temp_index());
   EffectGraphVisitor for_false(owner(), temp_index());
 
-  if (for_test.can_be_true()) {
-    node->true_branch()->Visit(&for_true);
-    // The for_false graph fragment will be empty (default graph fragment)
-    // if we do not call Visit.
-    if (node->false_branch() != NULL) node->false_branch()->Visit(&for_false);
-  }
+  node->true_branch()->Visit(&for_true);
+  // The for_false graph fragment will be empty (default graph fragment) if
+  // we do not call Visit.
+  if (node->false_branch() != NULL) node->false_branch()->Visit(&for_false);
   Join(for_test, for_true, for_false);
 }
 
 
 void EffectGraphVisitor::VisitSwitchNode(SwitchNode* node) {
   Bailout("EffectGraphVisitor::VisitSwitchNode");
 }
 
 
 void EffectGraphVisitor::VisitCaseNode(CaseNode* node) {
   Bailout("EffectGraphVisitor::VisitCaseNode");
 }
 
 
 // <Statement> ::= While { label:     SourceLabel
 //                         condition: <Expression>
 //                         body:      <Sequence> }
 void EffectGraphVisitor::VisitWhileNode(WhileNode* node) {
   TestGraphVisitor for_test(owner(), temp_index());
   node->condition()->Visit(&for_test);
 
   EffectGraphVisitor for_body(owner(), temp_index());
-  if (for_test.can_be_true()) node->body()->Visit(&for_body);
+  node->body()->Visit(&for_body);
   TieLoop(for_test, for_body);
 }
 
 
 void EffectGraphVisitor::VisitDoWhileNode(DoWhileNode* node) {
   EffectGraphVisitor for_body(owner(), temp_index());
   node->body()->Visit(&for_body);
   TestGraphVisitor for_test(owner(), temp_index());
   node->condition()->Visit(&for_test);
   ASSERT(is_open());
@@ skipping 916 matching lines @@
   char* chars = reinterpret_cast<char*>(
       Isolate::Current()->current_zone()->Allocate(len));
   OS::SNPrint(chars, len, kFormat, function_name, reason);
   const Error& error = Error::Handle(
       LanguageError::New(String::Handle(String::New(chars))));
   Isolate::Current()->long_jump_base()->Jump(1, error);
 }
 
 
 }  // namespace dart