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diff --git a/src/ir/branch-utils.h b/src/ir/branch-utils.h
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+/*
+ * Copyright 2017 WebAssembly Community Group participants
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef wasm_ir_branch_h
+#define wasm_ir_branch_h
+
+#include "wasm.h"
+#include "wasm-traversal.h"
+
+namespace wasm {
+
+namespace BranchUtils {
+
+// Some branches are obviously not actually reachable (e.g. (br $out (unreachable)))
+
+inline bool isBranchReachable(Break* br) {
+  return !(br->value     && br->value->type     == unreachable) &&
+         !(br->condition && br->condition->type == unreachable);
+}
+
+inline bool isBranchReachable(Switch* sw) {
+  return !(sw->value && sw->value->type     == unreachable) &&
+                        sw->condition->type != unreachable;
+}
+
+inline bool isBranchReachable(Expression* expr) {
+  if (auto* br = expr->dynCast<Break>()) {
+    return isBranchReachable(br);
+  } else if (auto* sw = expr->dynCast<Switch>()) {
+    return isBranchReachable(sw);
+  }
+  WASM_UNREACHABLE();
+}
+
+// returns the set of targets to which we branch that are
+// outside of a node
+inline std::set<Name> getExitingBranches(Expression* ast) {
+  struct Scanner : public PostWalker<Scanner> {
+    std::set<Name> targets;
+
+    void visitBreak(Break* curr) {
+      targets.insert(curr->name);
+    }
+    void visitSwitch(Switch* curr) {
+      for (auto target : targets) {
+        targets.insert(target);
+      }
+      targets.insert(curr->default_);
+    }
+    void visitBlock(Block* curr) {
+      if (curr->name.is()) {
+        targets.erase(curr->name);
+      }
+    }
+    void visitLoop(Loop* curr) {
+      if (curr->name.is()) {
+        targets.erase(curr->name);
+      }
+    }
+  };
+  Scanner scanner;
+  scanner.walk(ast);
+  // anything not erased is a branch out
+  return scanner.targets;
+}
+
+// returns the list of all branch targets in a node
+
+inline std::set<Name> getBranchTargets(Expression* ast) {
+  struct Scanner : public PostWalker<Scanner> {
+    std::set<Name> targets;
+
+    void visitBlock(Block* curr) {
+      if (curr->name.is()) {
+        targets.insert(curr->name);
+      }
+    }
+    void visitLoop(Loop* curr) {
+      if (curr->name.is()) {
+        targets.insert(curr->name);
+      }
+    }
+  };
+  Scanner scanner;
+  scanner.walk(ast);
+  return scanner.targets;
+}
+
+// Finds if there are branches targeting a name. Note that since names are
+// unique in our IR, we just need to look for the name, and do not need
+// to analyze scoping.
+// By default we consider all branches, so any place there is a branch that
+// names the target. You can unset 'named' to only note branches that appear
+// reachable (i.e., are not obviously unreachable).
+struct BranchSeeker : public PostWalker<BranchSeeker> {
+  Name target;
+  bool named = true;
+
+  Index found;
+  WasmType valueType;
+
+  BranchSeeker(Name target) : target(target), found(0) {}
+
+  void noteFound(Expression* value) {
+    found++;
+    if (found == 1) valueType = unreachable;
+    if (!value) valueType = none;
+    else if (value->type != unreachable) valueType = value->type;
+  }
+
+  void visitBreak(Break *curr) {
+    if (!named) {
+      // ignore an unreachable break
+      if (curr->condition && curr->condition->type == unreachable) return;
+      if (curr->value && curr->value->type == unreachable) return;
+    }
+    // check the break
+    if (curr->name == target) noteFound(curr->value);
+  }
+
+  void visitSwitch(Switch *curr) {
+    if (!named) {
+      // ignore an unreachable switch
+      if (curr->condition->type == unreachable) return;
+      if (curr->value && curr->value->type == unreachable) return;
+    }
+    // check the switch
+    for (auto name : curr->targets) {
+      if (name == target) noteFound(curr->value);
+    }
+    if (curr->default_ == target) noteFound(curr->value);
+  }
+
+  static bool hasReachable(Expression* tree, Name target) {
+    if (!target.is()) return false;
+    BranchSeeker seeker(target);
+    seeker.named = false;
+    seeker.walk(tree);
+    return seeker.found > 0;
+  }
+
+  static Index countReachable(Expression* tree, Name target) {
+    if (!target.is()) return 0;
+    BranchSeeker seeker(target);
+    seeker.named = false;
+    seeker.walk(tree);
+    return seeker.found;
+  }
+
+  static bool hasNamed(Expression* tree, Name target) {
+    if (!target.is()) return false;
+    BranchSeeker seeker(target);
+    seeker.walk(tree);
+    return seeker.found > 0;
+  }
+
+  static Index countNamed(Expression* tree, Name target) {
+    if (!target.is()) return 0;
+    BranchSeeker seeker(target);
+    seeker.walk(tree);
+    return seeker.found;
+  }
+};
+
+} // namespace BranchUtils
+
+} // namespace wasm
+
+#endif // wasm_ir_branch_h
+