3 files changed, 53 insertions, 25 deletions

diff --git a/src/ir/eh-utils.cpp b/src/ir/eh-utils.cpp
index 3d369573d..fe33b09c2 100644
--- a/src/ir/eh-utils.cpp
+++ b/src/ir/eh-utils.cpp
@@ -162,6 +162,37 @@ void handleBlockNestedPops(Function* func, Module& wasm) {
   TypeUpdating::handleNonDefaultableLocals(func, wasm);
 }
 
+Pop* findPop(Expression* expr) {
+  auto pops = findPops(expr);
+  if (pops.size() == 0) {
+    return nullptr;
+  }
+  assert(pops.size() == 1);
+  return pops[0];
+}
+
+SmallVector<Pop*, 1> findPops(Expression* expr) {
+  SmallVector<Pop*, 1> pops;
+  SmallVector<Expression*, 8> work;
+  work.push_back(expr);
+  while (!work.empty()) {
+    auto* curr = work.back();
+    work.pop_back();
+    if (auto* pop = curr->dynCast<Pop>()) {
+      pops.push_back(pop);
+    } else if (auto* try_ = curr->dynCast<Try>()) {
+      // We don't go into inner catch bodies; pops in inner catch bodies
+      // belong to the inner catches
+      work.push_back(try_->body);
+    } else {
+      for (auto* child : ChildIterator(curr)) {
+        work.push_back(child);
+      }
+    }
+  }
+  return pops;
+};
+
 } // namespace EHUtils
 
 } // namespace wasm
diff --git a/src/ir/eh-utils.h b/src/ir/eh-utils.h
index 25677a32e..79ccbc507 100644
--- a/src/ir/eh-utils.h
+++ b/src/ir/eh-utils.h
@@ -17,6 +17,7 @@
 #ifndef wasm_ir_eh_h
 #define wasm_ir_eh_h
 
+#include "support/small_vector.h"
 #include "wasm.h"
 
 namespace wasm {
@@ -40,6 +41,25 @@ void handleBlockNestedPop(Try* try_, Function* func, Module& wasm);
 // Calls handleBlockNestedPop for each 'Try's in a given function.
 void handleBlockNestedPops(Function* func, Module& wasm);
 
+// Given a catch body, find the pop corresponding to the catch. There might be
+// pops nested inside a try inside this catch, and we must ignore them, like
+// here:
+//
+//  (catch
+//    (pop) ;; we want this for the outer catch
+//    (try
+//      (catch
+//        (pop) ;; but we do not want this for the outer catch
+//
+// If there is no pop, which can happen if the tag has no params, then nullptr
+// is returned.
+Pop* findPop(Expression* expr);
+
+// Like findPop(), but it does *not* assume that the module validates. A catch
+// might therefore have any number of pops. This function is primarily useful in
+// the validator - normally you should call findPop(), above.
+SmallVector<Pop*, 1> findPops(Expression* expr);
+
 } // namespace EHUtils
 
 } // namespace wasm
diff --git a/src/wasm/wasm-validator.cpp b/src/wasm/wasm-validator.cpp
index 9845da72c..57b52e182 100644
--- a/src/wasm/wasm-validator.cpp
+++ b/src/wasm/wasm-validator.cpp
@@ -2165,29 +2165,6 @@ void FunctionValidator::visitTry(Try* curr) {
                 curr,
                 "try cannot have both catch and delegate at the same time");
 
-  // Given a catch body, find pops corresponding to the catch
-  auto findPops = [](Expression* expr) {
-    SmallVector<Pop*, 1> pops;
-    SmallVector<Expression*, 8> work;
-    work.push_back(expr);
-    while (!work.empty()) {
-      auto* curr = work.back();
-      work.pop_back();
-      if (auto* pop = curr->dynCast<Pop>()) {
-        pops.push_back(pop);
-      } else if (auto* try_ = curr->dynCast<Try>()) {
-        // We don't go into inner catch bodies; pops in inner catch bodies
-        // belong to the inner catches
-        work.push_back(try_->body);
-      } else {
-        for (auto* child : ChildIterator(curr)) {
-          work.push_back(child);
-        }
-      }
-    }
-    return pops;
-  };
-
   for (Index i = 0; i < curr->catchTags.size(); i++) {
     Name tagName = curr->catchTags[i];
     auto* tag = getModule()->getTagOrNull(tagName);
@@ -2196,7 +2173,7 @@ void FunctionValidator::visitTry(Try* curr) {
     }
 
     auto* catchBody = curr->catchBodies[i];
-    SmallVector<Pop*, 1> pops = findPops(catchBody);
+    auto pops = EHUtils::findPops(catchBody);
     if (tag->sig.params == Type::none) {
       if (!shouldBeTrue(pops.empty(), curr, "")) {
         getStream() << "catch's tag (" << tagName
@@ -2225,7 +2202,7 @@ void FunctionValidator::visitTry(Try* curr) {
 
   if (curr->hasCatchAll()) {
     auto* catchAllBody = curr->catchBodies.back();
-    shouldBeTrue(findPops(catchAllBody).empty(),
+    shouldBeTrue(EHUtils::findPops(catchAllBody).empty(),
                  curr,
                  "catch_all's body should not have pops");
   }