diff --git a/clang/lib/Basic/Targets/WebAssembly.h b/clang/lib/Basic/Targets/WebAssembly.h
--- a/clang/lib/Basic/Targets/WebAssembly.h
+++ b/clang/lib/Basic/Targets/WebAssembly.h
@@ -69,7 +69,8 @@
                         MacroBuilder &Builder) const override;
 
 private:
-  static void setSIMDLevel(llvm::StringMap<bool> &Features, SIMDEnum Level);
+  static void setSIMDLevel(llvm::StringMap<bool> &Features, SIMDEnum Level,
+                           bool Enabled);
 
   bool
   initFeatureMap(llvm::StringMap<bool> &Features, DiagnosticsEngine &Diags,
@@ -77,6 +78,9 @@
                  const std::vector<std::string> &FeaturesVec) const override;
   bool hasFeature(StringRef Feature) const final;
 
+  void setFeatureEnabled(llvm::StringMap<bool> &Features, StringRef Name,
+                         bool Enabled) const final;
+
   bool handleTargetFeatures(std::vector<std::string> &Features,
                             DiagnosticsEngine &Diags) final;
 
diff --git a/clang/lib/Basic/Targets/WebAssembly.cpp b/clang/lib/Basic/Targets/WebAssembly.cpp
--- a/clang/lib/Basic/Targets/WebAssembly.cpp
+++ b/clang/lib/Basic/Targets/WebAssembly.cpp
@@ -96,19 +96,43 @@
 }
 
 void WebAssemblyTargetInfo::setSIMDLevel(llvm::StringMap<bool> &Features,
-                                         SIMDEnum Level) {
+                                         SIMDEnum Level, bool Enabled) {
+  if (Enabled) {
+    switch (Level) {
+    case UnimplementedSIMD128:
+      Features["unimplemented-simd128"] = true;
+      LLVM_FALLTHROUGH;
+    case SIMD128:
+      Features["simd128"] = true;
+      LLVM_FALLTHROUGH;
+    case NoSIMD:
+      break;
+    }
+    return;
+  }
+
   switch (Level) {
-  case UnimplementedSIMD128:
-    Features["unimplemented-simd128"] = true;
-    LLVM_FALLTHROUGH;
+  case NoSIMD:
   case SIMD128:
-    Features["simd128"] = true;
+    Features["simd128"] = false;
     LLVM_FALLTHROUGH;
-  case NoSIMD:
+  case UnimplementedSIMD128:
+    Features["unimplemented-simd128"] = false;
     break;
   }
 }
 
+void WebAssemblyTargetInfo::setFeatureEnabled(llvm::StringMap<bool> &Features,
+                                              StringRef Name,
+                                              bool Enabled) const {
+  if (Name == "simd128")
+    setSIMDLevel(Features, SIMD128, Enabled);
+  else if (Name == "unimplemented-simd128")
+    setSIMDLevel(Features, UnimplementedSIMD128, Enabled);
+  else
+    Features[Name] = Enabled;
+}
+
 bool WebAssemblyTargetInfo::initFeatureMap(
     llvm::StringMap<bool> &Features, DiagnosticsEngine &Diags, StringRef CPU,
     const std::vector<std::string> &FeaturesVec) const {
@@ -119,30 +143,8 @@
     Features["atomics"] = true;
     Features["mutable-globals"] = true;
     Features["tail-call"] = true;
-    setSIMDLevel(Features, SIMD128);
+    setSIMDLevel(Features, SIMD128, true);
   }
-  // Other targets do not consider user-configured features here, but while we
-  // are actively developing new features it is useful to let user-configured
-  // features control availability of builtins
-  setSIMDLevel(Features, SIMDLevel);
-  if (HasNontrappingFPToInt)
-    Features["nontrapping-fptoint"] = true;
-  if (HasSignExt)
-    Features["sign-ext"] = true;
-  if (HasExceptionHandling)
-    Features["exception-handling"] = true;
-  if (HasBulkMemory)
-    Features["bulk-memory"] = true;
-  if (HasAtomics)
-    Features["atomics"] = true;
-  if (HasMutableGlobals)
-    Features["mutable-globals"] = true;
-  if (HasMultivalue)
-    Features["multivalue"] = true;
-  if (HasTailCall)
-    Features["tail-call"] = true;
-  if (HasReferenceTypes)
-    Features["reference-types"] = true;
 
   return TargetInfo::initFeatureMap(Features, Diags, CPU, FeaturesVec);
 }