diff --git a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
--- a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -129,6 +129,7 @@
 static const char *const kAsanModuleCtorName = "asan.module_ctor";
 static const char *const kAsanModuleDtorName = "asan.module_dtor";
 static const uint64_t kAsanCtorAndDtorPriority = 1;
+static const uint64_t kAsanEmscriptenCtorAndDtorPriority = 50;
 static const char *const kAsanReportErrorTemplate = "__asan_report_";
 static const char *const kAsanRegisterGlobalsName = "__asan_register_globals";
 static const char *const kAsanUnregisterGlobalsName =
@@ -530,6 +531,14 @@
   return std::max(32U, 1U << MappingScale);
 }
 
+static uint64_t GetCtorAndDtorPriority(Triple &TargetTriple) {
+  if (TargetTriple.isOSEmscripten()) {
+    return kAsanEmscriptenCtorAndDtorPriority;
+  } else {
+    return kAsanCtorAndDtorPriority;
+  }
+}
+
 namespace {
 
 /// Module analysis for getting various metadata about the module.
@@ -1768,6 +1777,8 @@
   if (!CA)
     return;
 
+  const uint64_t CtorAndDtorPriority = GetCtorAndDtorPriority(TargetTriple);
+
   for (Use &OP : CA->operands()) {
     if (isa<ConstantAggregateZero>(OP)) continue;
     ConstantStruct *CS = cast<ConstantStruct>(OP);
@@ -1777,7 +1788,8 @@
       if (F->getName() == kAsanModuleCtorName) continue;
       ConstantInt *Priority = dyn_cast<ConstantInt>(CS->getOperand(0));
       // Don't instrument CTORs that will run before asan.module_ctor.
-      if (Priority->getLimitedValue() <= kAsanCtorAndDtorPriority) continue;
+      if (Priority->getLimitedValue() <= CtorAndDtorPriority)
+        continue;
       poisonOneInitializer(*F, ModuleName);
     }
   }
@@ -2429,22 +2441,24 @@
     Changed |= InstrumentGlobals(IRB, M, &CtorComdat);
   }
 
+  const uint64_t CtorAndDtorPriority = GetCtorAndDtorPriority(TargetTriple);
+
   // Put the constructor and destructor in comdat if both
   // (1) global instrumentation is not TU-specific
   // (2) target is ELF.
   if (UseCtorComdat && TargetTriple.isOSBinFormatELF() && CtorComdat) {
     AsanCtorFunction->setComdat(M.getOrInsertComdat(kAsanModuleCtorName));
-    appendToGlobalCtors(M, AsanCtorFunction, kAsanCtorAndDtorPriority,
+    appendToGlobalCtors(M, AsanCtorFunction, CtorAndDtorPriority,
                         AsanCtorFunction);
     if (AsanDtorFunction) {
       AsanDtorFunction->setComdat(M.getOrInsertComdat(kAsanModuleDtorName));
-      appendToGlobalDtors(M, AsanDtorFunction, kAsanCtorAndDtorPriority,
+      appendToGlobalDtors(M, AsanDtorFunction, CtorAndDtorPriority,
                           AsanDtorFunction);
     }
   } else {
-    appendToGlobalCtors(M, AsanCtorFunction, kAsanCtorAndDtorPriority);
+    appendToGlobalCtors(M, AsanCtorFunction, CtorAndDtorPriority);
     if (AsanDtorFunction)
-      appendToGlobalDtors(M, AsanDtorFunction, kAsanCtorAndDtorPriority);
+      appendToGlobalDtors(M, AsanDtorFunction, CtorAndDtorPriority);
   }
 
   return Changed;