2 files changed, 30 insertions, 4 deletions
diff --git a/src/ir/names.h b/src/ir/names.h
index a589571bf..3d49a4a36 100644
--- a/src/ir/names.h
+++ b/src/ir/names.h
@@ -46,6 +46,33 @@ inline void ensureNames(Function* func) {
   }
 }
 
+// Given a root of a name, finds a valid name with perhaps a number appended
+// to it, by calling a function to check if a name is valid.
+inline Name
+getValidName(Module& module, Name root, std::function<bool(Name)> check) {
+  if (check(root)) {
+    return root;
+  }
+  auto prefixed = std::string(root.str) + '_';
+  Index num = 0;
+  while (1) {
+    auto name = prefixed + std::to_string(num);
+    if (check(name)) {
+      return name;
+    }
+    num++;
+  }
+}
+
+inline Name getValidGlobalName(Module& module, Name root) {
+  return getValidName(
+    module, root, [&](Name test) { return !module.getGlobalOrNull(test); });
+}
+inline Name getValidFunctionName(Module& module, Name root) {
+  return getValidName(
+    module, root, [&](Name test) { return !module.getFunctionOrNull(test); });
+}
+
 } // namespace Names
 
 } // namespace wasm
diff --git a/src/passes/MemoryPacking.cpp b/src/passes/MemoryPacking.cpp
index 6003274e8..d4d75e6d6 100644
--- a/src/passes/MemoryPacking.cpp
+++ b/src/passes/MemoryPacking.cpp
@@ -30,6 +30,7 @@
 
 #include "ir/manipulation.h"
 #include "ir/module-utils.h"
+#include "ir/names.h"
 #include "ir/utils.h"
 #include "pass.h"
 #include "support/space.h"
@@ -90,8 +91,6 @@ makeGtShiftedMemorySize(Builder& builder, Module& module, MemoryInit* curr) {
 } // anonymous namespace
 
 struct MemoryPacking : public Pass {
-  size_t dropStateGlobalCount = 0;
-
   // FIXME: Chrome has a bug decoding section indices that prevents it from
   // using more than 63. Just use WebLimitations::MaxDataSegments once this is
   // fixed. See https://bugs.chromium.org/p/v8/issues/detail?id=10151.
@@ -559,8 +558,8 @@ void MemoryPacking::createReplacements(Module* module,
     if (dropStateGlobal != Name()) {
       return dropStateGlobal;
     }
-    dropStateGlobal = Name(std::string("__mem_segment_drop_state_") +
-                           std::to_string(dropStateGlobalCount++));
+    dropStateGlobal =
+      Names::getValidGlobalName(*module, "__mem_segment_drop_state");
     module->addGlobal(builder.makeGlobal(dropStateGlobal,
                                          Type::i32,
                                          builder.makeConst(int32_t(0)),