Index: lib/Basic/LangOptions.cpp
===================================================================
--- lib/Basic/LangOptions.cpp
+++ lib/Basic/LangOptions.cpp
@@ -29,9 +29,11 @@
   Name = Default;
 #include "clang/Basic/LangOptions.def"
 
-  // FIXME: This should not be reset; modules can be different with different
-  // sanitizer options (this affects __has_feature(address_sanitizer) etc).
-  Sanitize.clear();
+  // FIXME: Some sanitizers do not expose any information via the preprocessor
+  // (e.g UBSan). We may be able to avoid some module rebuilds by disabling
+  // those sanitizers.
+
+  // These options do not affect AST generation.
   SanitizerBlacklistFiles.clear();
   XRayAlwaysInstrumentFiles.clear();
   XRayNeverInstrumentFiles.clear();
Index: lib/Frontend/CompilerInvocation.cpp
===================================================================
--- lib/Frontend/CompilerInvocation.cpp
+++ lib/Frontend/CompilerInvocation.cpp
@@ -2693,6 +2693,11 @@
     code = ext->hashExtension(code);
   }
 
+  // Extend the signature with the enabled sanitizers, if at least one is
+  // enabled.
+  if (!LangOpts->Sanitize.empty())
+    code = hash_combine(code, LangOpts->Sanitize.Mask);
+
   return llvm::APInt(64, code).toString(36, /*Signed=*/false);
 }
 
Index: test/Modules/Inputs/check-for-sanitizer-feature/check.h
===================================================================
--- /dev/null
+++ test/Modules/Inputs/check-for-sanitizer-feature/check.h
@@ -0,0 +1,5 @@
+#if __has_feature(address_sanitizer)
+#define HAS_ASAN 1
+#else
+#define HAS_ASAN 0
+#endif
Index: test/Modules/Inputs/check-for-sanitizer-feature/map
===================================================================
--- /dev/null
+++ test/Modules/Inputs/check-for-sanitizer-feature/map
@@ -0,0 +1,3 @@
+module check_feature {
+  header "check.h"
+}
Index: test/Modules/check-for-sanitizer-feature.cpp
===================================================================
--- /dev/null
+++ test/Modules/check-for-sanitizer-feature.cpp
@@ -0,0 +1,32 @@
+// RUN: rm -rf %t
+// RUN: mkdir %t
+
+// Build and use an ASan-enabled module.
+// RUN: %clang_cc1 -fsanitize=address -fmodules -fmodules-cache-path=%t \
+// RUN:   -fmodule-map-file=%S/Inputs/check-for-sanitizer-feature/map \
+// RUN:   -I %S/Inputs/check-for-sanitizer-feature -verify %s
+
+// Force a module rebuild by disabling ASan.
+// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t \
+// RUN:   -fmodule-map-file=%S/Inputs/check-for-sanitizer-feature/map \
+// RUN:   -I %S/Inputs/check-for-sanitizer-feature -verify %s
+
+// Force another module rebuild by enabling ASan again.
+// RUN: %clang_cc1 -fsanitize=address -fmodules -fmodules-cache-path=%t \
+// RUN:   -fmodule-map-file=%S/Inputs/check-for-sanitizer-feature/map \
+// RUN:   -I %S/Inputs/check-for-sanitizer-feature -verify %s
+
+#include "check.h"
+
+#if __has_feature(address_sanitizer)
+#if HAS_ASAN != 1
+#error Does not have the address_sanitizer feature, but should.
+#endif
+#else
+#if HAS_ASAN != 0
+#error Has the address_sanitizer feature, but shouldn't.
+#endif
+
+#endif
+
+// expected-no-diagnostics