Index: lld/wasm/Writer.cpp
===================================================================
--- lld/wasm/Writer.cpp
+++ lld/wasm/Writer.cpp
@@ -841,7 +841,7 @@
 void Writer::createInitMemoryFunction() {
   LLVM_DEBUG(dbgs() << "createInitMemoryFunction\n");
   assert(WasmSym::initMemoryFlag);
-  uint32_t flagAddress = WasmSym::initMemoryFlag->getVirtualAddress();
+  uint64_t flagAddress = WasmSym::initMemoryFlag->getVirtualAddress();
   std::string bodyContent;
   {
     raw_string_ostream os(bodyContent);
@@ -890,8 +890,10 @@
       //  ( ... drop data segments ... )
       // )
 
+      bool is64 = config->is64.getValueOr(false);
+
       // Atomically check whether this is the main thread.
-      writeI32Const(os, flagAddress, "flag address");
+      writePtrConst(os, flagAddress, is64, "flag address");
       writeI32Const(os, 0, "expected flag value");
       writeI32Const(os, 1, "flag value");
       writeU8(os, WASM_OPCODE_ATOMICS_PREFIX, "atomics prefix");
@@ -901,9 +903,10 @@
       writeU8(os, WASM_TYPE_NORESULT, "blocktype");
 
       // Did not increment 0, so wait for main thread to initialize memory
-      writeI32Const(os, flagAddress, "flag address");
+      writePtrConst(os, flagAddress, is64, "flag address");
       writeI32Const(os, 1, "expected flag value");
       writeI64Const(os, -1, "timeout");
+
       writeU8(os, WASM_OPCODE_ATOMICS_PREFIX, "atomics prefix");
       writeUleb128(os, WASM_OPCODE_I32_ATOMIC_WAIT, "i32.atomic.wait");
       writeMemArg(os, 2, 0);
@@ -915,12 +918,7 @@
       for (const OutputSegment *s : segments) {
         if (needsPassiveInitialization(s)) {
           // destination address
-          if (config->is64.getValueOr(false)) {
-            writeI64Const(os, s->startVA, "destination address");
-          } else {
-            writeI32Const(os, static_cast<int32_t>(s->startVA),
-                          "destination address");
-          }
+          writePtrConst(os, s->startVA, is64, "destination address");
           // source segment offset
           writeI32Const(os, 0, "segment offset");
           // memory region size
@@ -934,14 +932,14 @@
       }
 
       // Set flag to 2 to mark end of initialization
-      writeI32Const(os, flagAddress, "flag address");
+      writePtrConst(os, flagAddress, is64, "flag address");
       writeI32Const(os, 2, "flag value");
       writeU8(os, WASM_OPCODE_ATOMICS_PREFIX, "atomics prefix");
       writeUleb128(os, WASM_OPCODE_I32_ATOMIC_STORE, "i32.atomic.store");
       writeMemArg(os, 2, 0);
 
       // Notify any waiters that memory initialization is complete
-      writeI32Const(os, flagAddress, "flag address");
+      writePtrConst(os, flagAddress, is64, "flag address");
       writeI32Const(os, -1, "number of waiters");
       writeU8(os, WASM_OPCODE_ATOMICS_PREFIX, "atomics prefix");
       writeUleb128(os, WASM_OPCODE_ATOMIC_NOTIFY, "atomic.notify");
Index: lld/wasm/WriterUtils.h
===================================================================
--- lld/wasm/WriterUtils.h
+++ lld/wasm/WriterUtils.h
@@ -40,6 +40,9 @@
 
 void writeI64Const(raw_ostream &os, int64_t number, const Twine &msg);
 
+void writePtrConst(raw_ostream &os, int64_t number, bool is64,
+                   const Twine &msg);
+
 void writeMemArg(raw_ostream &os, uint32_t alignment, uint64_t offset);
 
 void writeInitExpr(raw_ostream &os, const llvm::wasm::WasmInitExpr &initExpr);
Index: lld/wasm/WriterUtils.cpp
===================================================================
--- lld/wasm/WriterUtils.cpp
+++ lld/wasm/WriterUtils.cpp
@@ -136,6 +136,14 @@
   writeSleb128(os, number, msg);
 }
 
+void writePtrConst(raw_ostream &os, int64_t number, bool is64,
+                   const Twine &msg) {
+  if (is64)
+    writeI64Const(os, number, msg);
+  else
+    writeI32Const(os, static_cast<int32_t>(number), msg);
+}
+
 void writeMemArg(raw_ostream &os, uint32_t alignment, uint64_t offset) {
   writeUleb128(os, alignment, "alignment");
   writeUleb128(os, offset, "offset");