New compiler: implement switch/case in graph builder.

runtime/vm/flow_graph_builder.cc

Index: runtime/vm/flow_graph_builder.cc
===================================================================
--- runtime/vm/flow_graph_builder.cc	(revision 6099)
+++ runtime/vm/flow_graph_builder.cc	(working copy)
@@ -701,12 +701,144 @@
 
 
 void EffectGraphVisitor::VisitSwitchNode(SwitchNode* node) {
-  Bailout("EffectGraphVisitor::VisitSwitchNode");
+  EffectGraphVisitor switch_body(owner(), temp_index());
+  node->body()->Visit(&switch_body);
+  Append(switch_body);
+  if ((node->label() != NULL) && (node->label()->join_for_break() != NULL)) {
+    if (is_open()) {
+      AddInstruction(node->label()->join_for_break());
+    } else {
+      exit_ = node->label()->join_for_break();
+    }
+  }
+  // No continue label allowed.
+  ASSERT((node->label() == NULL) ||
+         (node->label()->join_for_continue() == NULL));
 }
 
 
+// A case node contains zero or more case expressions, can contain default
+// and a case statement body.
+// Compose fragment as follows:
+// - if no case expressions, must have default:
+//   a) target
+//   b) [ case-statements ]
+//
+// - if has 1 or more case statements
+//   a) target-0
+//   b) [ case-expression-0 ] -> (true-target-0, target-1)
+//   c) target-1
+//   d) [ case-expression-1 ] -> (true-target-1, exit-target)
+//   e) true-target-0 -> case-statements-join
+//   f) true-target-1 -> case-statements-join
+//   g) case-statements-join
+//   h) [ case-statements ] -> exit-join
+//   i) exit-target -> exit-join
+//   j) exit-join
+//
+// Note: The specification of switch/case is under discussion and may change
+// drastically.
 void EffectGraphVisitor::VisitCaseNode(CaseNode* node) {
-  Bailout("EffectGraphVisitor::VisitCaseNode");
+  const intptr_t len = node->case_expressions()->length();
+  // Create case statements instructions.
+  const bool needs_join_at_statement_entry =
+      (len > 1) || ((len > 0) && (node->contains_default()));
+  EffectGraphVisitor for_case_statements(owner(), temp_index());
+  // Compute start of statements fragment.
+  BlockEntryInstr* statement_start = NULL;
+  if ((node->label() != NULL) && (node->label()->is_continue_target())) {
+    // Since a labeled jump continue statement occur in a different case node,
+    // allocate JoinNode here and use it as statement start.
+    if (node->label()->join_for_continue() == NULL) {
+      node->label()->set_join_for_continue(new JoinEntryInstr());
+    }
+    statement_start = node->label()->join_for_continue();
+  } else if (needs_join_at_statement_entry) {
+    statement_start = new JoinEntryInstr();
+  } else {
+    statement_start = new TargetEntryInstr();
+  }
+  for_case_statements.AddInstruction(statement_start);
+  node->statements()->Visit(&for_case_statements);
+  if (is_open() && (len == 0)) {
+    ASSERT(node->contains_default());
+    // Default only case node.
+    Append(for_case_statements);
+    return;
+  }
+
+  // Generate instructions for all case expressions and collect data to
+  // connect them.
+  GrowableArray<TargetEntryInstr**> case_true_addresses;
+  GrowableArray<TargetEntryInstr**> case_false_addresses;
+  GrowableArray<TargetEntryInstr*> case_entries;
+  for (intptr_t i = 0; i < len; i++) {
+    AstNode* case_expr = node->case_expressions()->NodeAt(i);
+    TestGraphVisitor for_case_expression(owner(), temp_index());
+    if (i == 0) {
+      case_entries.Add(NULL);  // Not to be used
+      case_expr->Visit(&for_case_expression);
+      // Append only the first one, everything else is connected from it.
+      Append(for_case_expression);
+    } else {
+      TargetEntryInstr* case_entry_target = new TargetEntryInstr();
+      case_entries.Add(case_entry_target);
+      for_case_expression.AddInstruction(case_entry_target);
+      case_expr->Visit(&for_case_expression);
+    }
+    case_true_addresses.Add(for_case_expression.true_successor_address());
+    case_false_addresses.Add(for_case_expression.false_successor_address());
+  }
+
+  // Once a test fragment has been added, this fragment is closed.
+  ASSERT(!is_open());

[regis, 2012/04/04 01:31:08]

Can you move this ASSERT up inside the loop? Each for_case_expression should be
closed, right?

[srdjan, 2012/04/04 17:33:00]

Discussed offline, leaving it here. Checking that we have added a fragment to
'this' EffectGraphVisitor' which has closed it.

+
+  // Connect all test cases except the last one.
+  for (intptr_t i = 0; i < (len - 1); i++) {
+    ASSERT(needs_join_at_statement_entry);
+    *case_false_addresses[i] = case_entries[i + 1];
+    TargetEntryInstr* true_target = new TargetEntryInstr();
+    *case_true_addresses[i] = true_target;
+    true_target->SetSuccessor(statement_start);
+  }
+
+  BlockEntryInstr* exit_instruction = NULL;
+  // Handle last (or only) case: false goes to exit or to statement if this
+  // node contains default.
+  if (len > 0) {
+    if (statement_start->IsTargetEntry()) {
+      *case_true_addresses[len - 1] = statement_start->AsTargetEntry();
+    } else {
+      TargetEntryInstr* true_target = new TargetEntryInstr();
+      *case_true_addresses[len - 1] = true_target;
+      true_target->SetSuccessor(statement_start);
+    }
+    TargetEntryInstr* false_target = new TargetEntryInstr();
+    *case_false_addresses[len - 1] = false_target;
+    if (node->contains_default()) {
+      // True and false go to statement start.
+      false_target->SetSuccessor(statement_start);
+      if (for_case_statements.is_open()) {
+        exit_instruction = new TargetEntryInstr();
+        for_case_statements.exit()->SetSuccessor(exit_instruction);
+      }
+    } else {
+      if (for_case_statements.is_open()) {
+        exit_instruction = new JoinEntryInstr();
+        for_case_statements.exit()->SetSuccessor(exit_instruction);
+      } else {
+        exit_instruction = new TargetEntryInstr();
+      }
+      false_target->SetSuccessor(exit_instruction);
+    }
+  } else {
+    // A CaseNode without case expressions must contain default.
+    ASSERT(node->contains_default());
+    AddInstruction(statement_start);
+  }
+
+  ASSERT(!is_open());
+  exit_ = exit_instruction;
 }