diff --git a/clang/include/clang/Lex/PreprocessorOptions.h b/clang/include/clang/Lex/PreprocessorOptions.h
--- a/clang/include/clang/Lex/PreprocessorOptions.h
+++ b/clang/include/clang/Lex/PreprocessorOptions.h
@@ -69,6 +69,9 @@
   std::vector<std::string> Includes;
   std::vector<std::string> MacroIncludes;
 
+  /// Perform extra checks when loading PCM files for mutable file systems.
+  bool ModulesCheckRelocated = true;
+
   /// Initialize the preprocessor with the compiler and target specific
   /// predefines.
   bool UsePredefines = true;
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -2990,6 +2990,9 @@
       BaseDirectoryAsWritten = Blob;
       assert(!F.ModuleName.empty() &&
              "MODULE_DIRECTORY found before MODULE_NAME");
+      F.BaseDirectory = std::string(Blob);
+      if (!PP.getPreprocessorOpts().ModulesCheckRelocated)
+        break;
       // If we've already loaded a module map file covering this module, we may
       // have a better path for it (relative to the current build).
       Module *M = PP.getHeaderSearchInfo().lookupModule(
@@ -3011,8 +3014,6 @@
           }
         }
         F.BaseDirectory = std::string(M->Directory->getName());
-      } else {
-        F.BaseDirectory = std::string(Blob);
       }
       break;
     }
@@ -3990,7 +3991,8 @@
   // usable header search context.
   assert(!F.ModuleName.empty() &&
          "MODULE_NAME should come before MODULE_MAP_FILE");
-  if (F.Kind == MK_ImplicitModule && ModuleMgr.begin()->Kind != MK_MainFile) {
+  if (PP.getPreprocessorOpts().ModulesCheckRelocated &&
+      F.Kind == MK_ImplicitModule && ModuleMgr.begin()->Kind != MK_MainFile) {
     // An implicitly-loaded module file should have its module listed in some
     // module map file that we've already loaded.
     Module *M =
diff --git a/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp b/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp
--- a/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp
+++ b/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp
@@ -253,6 +253,9 @@
     // context hashing.
     ScanInstance.getHeaderSearchOpts().ModulesStrictContextHash = true;
 
+    // Avoid some checks and module map parsing when loading PCM files.
+    ScanInstance.getPreprocessorOpts().ModulesCheckRelocated = false;
+
     std::unique_ptr<FrontendAction> Action;
 
     if (ModuleName)
diff --git a/clang/test/ClangScanDeps/header-search-pruning-transitive.c b/clang/test/ClangScanDeps/header-search-pruning-transitive.c
--- a/clang/test/ClangScanDeps/header-search-pruning-transitive.c
+++ b/clang/test/ClangScanDeps/header-search-pruning-transitive.c
@@ -72,8 +72,8 @@
 // CHECK:            ],
 // CHECK-NEXT:       "context-hash": "[[HASH_X:.*]]",
 // CHECK-NEXT:       "file-deps": [
-// CHECK-NEXT:         "[[PREFIX]]/./X.h",
-// CHECK-NEXT:         "[[PREFIX]]/./module.modulemap"
+// CHECK-NEXT:         "[[PREFIX]]/X.h",
+// CHECK-NEXT:         "[[PREFIX]]/module.modulemap"
 // CHECK-NEXT:       ],
 // CHECK-NEXT:       "name": "X"
 // CHECK-NEXT:     },
@@ -84,11 +84,11 @@
 // CHECK:            ],
 // CHECK-NEXT:       "context-hash": "[[HASH_Y_WITH_A]]",
 // CHECK-NEXT:       "file-deps": [
-// CHECK-NEXT:         "[[PREFIX]]/./Y.h",
-// CHECK-NEXT:         "[[PREFIX]]/./a/a.h",
-// CHECK-NEXT:         "[[PREFIX]]/./begin/begin.h",
-// CHECK-NEXT:         "[[PREFIX]]/./end/end.h",
-// CHECK-NEXT:         "[[PREFIX]]/./module.modulemap"
+// CHECK-NEXT:         "[[PREFIX]]/Y.h",
+// CHECK-NEXT:         "[[PREFIX]]/a/a.h",
+// CHECK-NEXT:         "[[PREFIX]]/begin/begin.h",
+// CHECK-NEXT:         "[[PREFIX]]/end/end.h",
+// CHECK-NEXT:         "[[PREFIX]]/module.modulemap"
 // CHECK-NEXT:       ],
 // CHECK-NEXT:       "name": "Y"
 // CHECK-NEXT:     }
@@ -126,8 +126,8 @@
 // also has a different context hash from the first version of module X.
 // CHECK-NOT:        "context-hash": "[[HASH_X]]",
 // CHECK:            "file-deps": [
-// CHECK-NEXT:         "[[PREFIX]]/./X.h",
-// CHECK-NEXT:         "[[PREFIX]]/./module.modulemap"
+// CHECK-NEXT:         "[[PREFIX]]/X.h",
+// CHECK-NEXT:         "[[PREFIX]]/module.modulemap"
 // CHECK-NEXT:       ],
 // CHECK-NEXT:       "name": "X"
 // CHECK-NEXT:     },
@@ -138,10 +138,10 @@
 // CHECK:            ],
 // CHECK-NEXT:       "context-hash": "[[HASH_Y_WITHOUT_A]]",
 // CHECK-NEXT:       "file-deps": [
-// CHECK-NEXT:         "[[PREFIX]]/./Y.h",
-// CHECK-NEXT:         "[[PREFIX]]/./begin/begin.h",
-// CHECK-NEXT:         "[[PREFIX]]/./end/end.h",
-// CHECK-NEXT:         "[[PREFIX]]/./module.modulemap"
+// CHECK-NEXT:         "[[PREFIX]]/Y.h",
+// CHECK-NEXT:         "[[PREFIX]]/begin/begin.h",
+// CHECK-NEXT:         "[[PREFIX]]/end/end.h",
+// CHECK-NEXT:         "[[PREFIX]]/module.modulemap"
 // CHECK-NEXT:       ],
 // CHECK-NEXT:       "name": "Y"
 // CHECK-NEXT:     }