add the option to seek named breaks, not just taken breaks; refactor headers to make this practical

1 files changed, 75 insertions, 0 deletions

diff --git a/src/ast/branch-utils.h b/src/ast/branch-utils.h
index 853b998af..77ec70753 100644
--- a/src/ast/branch-utils.h
+++ b/src/ast/branch-utils.h
@@ -100,6 +100,81 @@ inline std::set<Name> getBranchTargets(Expression* 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 ignore untaken branches. You can set named to
+// note those as well, then any named branch is noted, even if untaken
+struct BranchSeeker : public PostWalker<BranchSeeker> {
+  Name target;
+  bool named = false;
+
+  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 has(Expression* tree, Name target) {
+    if (!target.is()) return false;
+    BranchSeeker seeker(target);
+    seeker.walk(tree);
+    return seeker.found > 0;
+  }
+
+  static Index count(Expression* tree, Name target) {
+    if (!target.is()) return 0;
+    BranchSeeker seeker(target);
+    seeker.walk(tree);
+    return seeker.found;
+  }
+
+  static bool hasNamed(Expression* tree, Name target) {
+    if (!target.is()) return false;
+    BranchSeeker seeker(target);
+    seeker.named = true;
+    seeker.walk(tree);
+    return seeker.found > 0;
+  }
+
+  static Index countNamed(Expression* tree, Name target) {
+    if (!target.is()) return 0;
+    BranchSeeker seeker(target);
+    seeker.named = true;
+    seeker.walk(tree);
+    return seeker.found;
+  }
+};
+
 } // namespace BranchUtils
 
 } // namespace wasm