2 files changed, 9 insertions, 0 deletions
diff --git a/lib/Driver/ToolChains/WebAssembly.cpp b/lib/Driver/ToolChains/WebAssembly.cpp
index 1464c150c9..d00d833fbb 100644
--- a/lib/Driver/ToolChains/WebAssembly.cpp
+++ b/lib/Driver/ToolChains/WebAssembly.cpp
@@ -135,6 +135,14 @@ void WebAssembly::AddClangCXXStdlibIncludeArgs(const ArgList &DriverArgs,
                      getDriver().SysRoot + "/include/c++/v1");
 }
 
+std::string WebAssembly::getThreadModel() const {
+  // The WebAssembly MVP does not yet support threads; for now, use the
+  // "single" threading model, which lowers atomics to non-atomic operations.
+  // When threading support is standardized and implemented in popular engines,
+  // this override should be removed.
+  return "single";
+}
+
 Tool *WebAssembly::buildLinker() const {
   return new tools::wasm::Linker(*this);
 }
diff --git a/lib/Driver/ToolChains/WebAssembly.h b/lib/Driver/ToolChains/WebAssembly.h
index 7524361d51..8784e12dfb 100644
--- a/lib/Driver/ToolChains/WebAssembly.h
+++ b/lib/Driver/ToolChains/WebAssembly.h
@@ -62,6 +62,7 @@ private:
   void AddClangCXXStdlibIncludeArgs(
       const llvm::opt::ArgList &DriverArgs,
       llvm::opt::ArgStringList &CC1Args) const override;
+  std::string getThreadModel() const override;
 
   const char *getDefaultLinker() const override {
     return "lld";