Do not use recursion for depth-first traversal of straight line code.

runtime/vm/intermediate_language.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/intermediate_language.h"
 
 #include "vm/object.h"
 #include "vm/os.h"
 #include "vm/scopes.h"
 
@@ skipping 101 matching lines @@
   // 3. The last entry in the preorder array is the spanning-tree parent.
   parent->Add(preorder->Last());
 
   // 4. Assign preorder number and add the block entry to the list.
   set_preorder_number(preorder->length());
   preorder->Add(this);
   // The preorder and parent arrays are both indexed by preorder block
   // number, so they should stay in lockstep.
   ASSERT(preorder->length() == parent->length());
 
-  // 5. Recursively visit the successor.
+  // 5. Iterate straight-line successors until a branch instruction or
+  // another basic block entry instruction, and visit that instruction.
   ASSERT(successor_ != NULL);
-  successor_->DiscoverBlocks(this, preorder, postorder, parent);
+  Instruction* next = successor_;
+  while ((next != NULL) && !next->IsBlockEntry() && !next->IsBranch()) {
+    set_last_instruction(next);
+    next = next->StraightLineSuccessor();
+  }
+  if (next != NULL) {
+    next->DiscoverBlocks(this, preorder, postorder, parent);
+  }
 
   // 6. Assign postorder number and add the block entry to the list.
   set_postorder_number(postorder->length());
   postorder->Add(this);
 }
 
 
 void TargetEntryInstr::DiscoverBlocks(
     BlockEntryInstr* current_block,
     GrowableArray<BlockEntryInstr*>* preorder,
@@ skipping 10 matching lines @@
   // The global graph entry has a NULL parent.
   parent->Add(preorder->is_empty() ? NULL : preorder->Last());
 
   // 4. Assign preorder number and add the block entry to the list.
   set_preorder_number(preorder->length());
   preorder->Add(this);
   // The preorder and parent arrays are indexed by preorder block number, so
   // they should stay in lockstep.
   ASSERT(preorder->length() == parent->length());
 
-  // 5. Recursively visit the successor.
+  // 5. Iterate straight-line successors until a branch instruction or
+  // another basic block entry instruction, and visit that instruction.
   ASSERT(successor_ != NULL);
-  successor_->DiscoverBlocks(this, preorder, postorder, parent);
+  Instruction* next = successor_;
+  while ((next != NULL) &&
+         !next->IsBlockEntry() &&
+         !next->IsBranch()) {
+    set_last_instruction(next);
+    next = next->StraightLineSuccessor();
+  }
+  if (next != NULL) {
+    next->DiscoverBlocks(this, preorder, postorder, parent);
+  }
 
   // 6. Assign postorder number and add the block entry to the list.
   set_postorder_number(postorder->length());
   postorder->Add(this);
 }
 
 
-void PickTempInstr::DiscoverBlocks(
-    BlockEntryInstr* current_block,
-    GrowableArray<BlockEntryInstr*>* preorder,
-    GrowableArray<BlockEntryInstr*>* postorder,
-    GrowableArray<BlockEntryInstr*>* parent) {
-  current_block->set_last_instruction(this);
-  ASSERT(successor_ != NULL);
-  successor_->DiscoverBlocks(current_block, preorder, postorder, parent);
-}
-
-
-void TuckTempInstr::DiscoverBlocks(
-    BlockEntryInstr* current_block,
-    GrowableArray<BlockEntryInstr*>* preorder,
-    GrowableArray<BlockEntryInstr*>* postorder,
-    GrowableArray<BlockEntryInstr*>* parent) {
-  current_block->set_last_instruction(this);
-  ASSERT(successor_ != NULL);
-  successor_->DiscoverBlocks(current_block, preorder, postorder, parent);
-}
-
-
-void DoInstr::DiscoverBlocks(
-    BlockEntryInstr* current_block,
-    GrowableArray<BlockEntryInstr*>* preorder,
-    GrowableArray<BlockEntryInstr*>* postorder,
-    GrowableArray<BlockEntryInstr*>* parent) {
-  current_block->set_last_instruction(this);
-  ASSERT(successor_ != NULL);
-  successor_->DiscoverBlocks(current_block, preorder, postorder, parent);
-}
-
-
-void BindInstr::DiscoverBlocks(
-    BlockEntryInstr* current_block,
-    GrowableArray<BlockEntryInstr*>* preorder,
-    GrowableArray<BlockEntryInstr*>* postorder,
-    GrowableArray<BlockEntryInstr*>* parent) {
-  current_block->set_last_instruction(this);
-  ASSERT(successor_ != NULL);
-  successor_->DiscoverBlocks(current_block, preorder, postorder, parent);
-}
-
-
-void ReturnInstr::DiscoverBlocks(
-    BlockEntryInstr* current_block,
-    GrowableArray<BlockEntryInstr*>* preorder,
-    GrowableArray<BlockEntryInstr*>* postorder,
-    GrowableArray<BlockEntryInstr*>* parent) {
-  current_block->set_last_instruction(this);
-}
-
-
-void ThrowInstr::DiscoverBlocks(
-    BlockEntryInstr* current_block,
-    GrowableArray<BlockEntryInstr*>* preorder,
-    GrowableArray<BlockEntryInstr*>* postorder,
-    GrowableArray<BlockEntryInstr*>* parent) {
-  current_block->set_last_instruction(this);
-}
-
-
-void ReThrowInstr::DiscoverBlocks(
-    BlockEntryInstr* current_block,
-    GrowableArray<BlockEntryInstr*>* preorder,
-    GrowableArray<BlockEntryInstr*>* postorder,
-    GrowableArray<BlockEntryInstr*>* parent) {
-  current_block->set_last_instruction(this);
-}
-
-
 void BranchInstr::DiscoverBlocks(
     BlockEntryInstr* current_block,
     GrowableArray<BlockEntryInstr*>* preorder,
     GrowableArray<BlockEntryInstr*>* postorder,
     GrowableArray<BlockEntryInstr*>* parent) {
   current_block->set_last_instruction(this);
   // Visit the false successor before the true successor so they appear in
   // true/false order in reverse postorder used as the block ordering in the
   // nonoptimizing compiler.
   ASSERT(true_successor_ != NULL);
   ASSERT(false_successor_ != NULL);
   false_successor_->DiscoverBlocks(current_block, preorder, postorder, parent);
   true_successor_->DiscoverBlocks(current_block, preorder, postorder, parent);
 }
 
 
 }  // namespace dart