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

runtime/vm/intermediate_language.cc

Index: runtime/vm/intermediate_language.cc
diff --git a/runtime/vm/intermediate_language.cc b/runtime/vm/intermediate_language.cc
index 8fc6e01d85f6dea53704d9eefbc56e93885e7111..0721fc595f540d9caa02cd79bea22119dcf035a5 100644
--- a/runtime/vm/intermediate_language.cc
+++ b/runtime/vm/intermediate_language.cc
@@ -119,9 +119,17 @@ void JoinEntryInstr::DiscoverBlocks(
   // 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());
@@ -152,9 +160,19 @@ void TargetEntryInstr::DiscoverBlocks(
   // 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());
@@ -162,77 +180,6 @@ void TargetEntryInstr::DiscoverBlocks(
 }
 
 
-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,