Index: clang/include/clang/Basic/DiagnosticGroups.td
===================================================================
--- clang/include/clang/Basic/DiagnosticGroups.td
+++ clang/include/clang/Basic/DiagnosticGroups.td
@@ -351,6 +351,7 @@
 def MismatchedTags : DiagGroup<"mismatched-tags">;
 def MissingFieldInitializers : DiagGroup<"missing-field-initializers">;
 def ModuleBuild : DiagGroup<"module-build">;
+def ModuleImport : DiagGroup<"module-import">;
 def ModuleConflict : DiagGroup<"module-conflict">;
 def ModuleFileExtension : DiagGroup<"module-file-extension">;
 def NewlineEOF : DiagGroup<"newline-eof">;
Index: clang/include/clang/Basic/DiagnosticSerializationKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSerializationKinds.td
+++ clang/include/clang/Basic/DiagnosticSerializationKinds.td
@@ -72,6 +72,10 @@
 def err_module_file_not_module : Error<
   "AST file '%0' was not built as a module">, DefaultFatal;
 
+def remark_module_import : Remark<
+  "importing module '%0'%select{| into '%3'}2 from '%1'">,
+  InGroup<ModuleImport>;
+
 def err_imported_module_not_found : Error<
     "module '%0' in AST file '%1' (imported by AST file '%2') "
     "is not defined in any loaded module map file; "
Index: clang/lib/Serialization/ASTReader.cpp
===================================================================
--- clang/lib/Serialization/ASTReader.cpp
+++ clang/lib/Serialization/ASTReader.cpp
@@ -2610,6 +2610,9 @@
 
     case MODULE_NAME:
       F.ModuleName = Blob;
+      Diag(diag::remark_module_import)
+          << F.ModuleName << F.FileName << (ImportedBy ? true : false)
+          << (ImportedBy ? StringRef(ImportedBy->ModuleName) : StringRef());
       if (Listener)
         Listener->ReadModuleName(F.ModuleName);
 
@@ -4141,6 +4144,9 @@
 
   switch (AddResult) {
   case ModuleManager::AlreadyLoaded:
+    Diag(diag::remark_module_import)
+        << M->ModuleName << M->FileName << (ImportedBy ? true : false)
+        << (ImportedBy ? StringRef(ImportedBy->ModuleName) : StringRef());
     return Success;
 
   case ModuleManager::NewlyLoaded:
Index: clang/test/Modules/Inputs/Rmodule-import/A.h
===================================================================
--- /dev/null
+++ clang/test/Modules/Inputs/Rmodule-import/A.h
@@ -0,0 +1,2 @@
+// A
+#include "B.h"
Index: clang/test/Modules/Inputs/Rmodule-import/B.h
===================================================================
--- /dev/null
+++ clang/test/Modules/Inputs/Rmodule-import/B.h
@@ -0,0 +1,2 @@
+// B
+#include "C.h"
Index: clang/test/Modules/Inputs/Rmodule-import/C.h
===================================================================
--- /dev/null
+++ clang/test/Modules/Inputs/Rmodule-import/C.h
@@ -0,0 +1 @@
+// C
Index: clang/test/Modules/Inputs/Rmodule-import/D.h
===================================================================
--- /dev/null
+++ clang/test/Modules/Inputs/Rmodule-import/D.h
@@ -0,0 +1 @@
+// D
Index: clang/test/Modules/Inputs/Rmodule-import/module.modulemap
===================================================================
--- /dev/null
+++ clang/test/Modules/Inputs/Rmodule-import/module.modulemap
@@ -0,0 +1,4 @@
+module A { header "A.h" }
+module B { header "B.h" }
+module C { header "C.h" }
+module D { header "D.h" }
Index: clang/test/Modules/Rmodule-build.m
===================================================================
--- clang/test/Modules/Rmodule-build.m
+++ clang/test/Modules/Rmodule-build.m
@@ -19,10 +19,6 @@
 // RUN: %clang_cc1 -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -fsyntax-only %s -I %t \
 // RUN:            -Rmodule-build 2>&1 | FileCheck %s
 
-// RUN: echo ' ' >> %t/C.h
-// RUN: %clang_cc1 -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -fsyntax-only %s -I %t \
-// RUN:            -Reverything 2>&1 | FileCheck %s
-
 // RUN: echo ' ' >> %t/B.h
 // RUN: %clang_cc1 -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -fsyntax-only %s -I %t \
 // RUN:            2>&1 | FileCheck -allow-empty -check-prefix=NO-REMARKS %s
Index: clang/test/Modules/Rmodule-import.m
===================================================================
--- /dev/null
+++ clang/test/Modules/Rmodule-import.m
@@ -0,0 +1,46 @@
+// RUN: rm -rf %t1 %t2
+
+// Run with -verify, which onliy gets remarks from the main TU.
+//
+// RUN: %clang_cc1 -fmodules -fimplicit-module-maps -fmodules-cache-path=%t1 \
+// RUN:     -fdisable-module-hash -fsyntax-only -I%S/Inputs/Rmodule-import \
+// RUN:     -Rmodule-build -Rmodule-import -verify %s
+
+// Run again, using FileCheck to check remarks from the module builds.
+//
+// RUN: %clang_cc1 -fmodules -fimplicit-module-maps -fmodules-cache-path=%t2 \
+// RUN:     -fdisable-module-hash -fsyntax-only -I%S/Inputs/Rmodule-import \
+// RUN:     -Rmodule-build -Rmodule-import %s 2>&1 |\
+// RUN: FileCheck %s -implicit-check-not "remark:"
+
+#include "A.h" // \
+   expected-remark-re{{building module 'A' as '{{.*}}/A.pcm'}} \
+   expected-remark{{finished building module 'A'}} \
+   expected-remark-re{{importing module 'A' from '{{.*}}/A.pcm'}} \
+   expected-remark-re{{importing module 'B' into 'A' from '{{.*}}/B.pcm'}} \
+   expected-remark-re{{importing module 'C' into 'B' from '{{.*}}/C.pcm'}}
+// CHECK: remark: building module 'A'
+// CHECK: remark: building module 'B'
+// CHECK: remark: building module 'C'
+// CHECK: remark: finished building module 'C'
+// CHECK: remark: importing module 'C' from '{{.*}}/C.pcm'
+// CHECK: remark: finished building module 'B'
+// CHECK: remark: importing module 'B' from '{{.*}}/B.pcm'
+// CHECK: remark: importing module 'C' into 'B' from '{{.*}}/C.pcm'
+// CHECK: remark: finished building module 'A'
+// CHECK: remark: importing module 'A' from '{{.*}}/A.pcm'
+// CHECK: remark: importing module 'B' into 'A' from '{{.*}}/B.pcm'
+// CHECK: remark: importing module 'C' into 'B' from '{{.*}}/C.pcm'
+#include "B.h" // \
+   expected-remark-re{{importing module 'B' from '{{.*}}/B.pcm'}}
+// CHECK: remark: importing module 'B' from '{{.*}}/B.pcm'
+#include "C.h" // \
+   expected-remark-re{{importing module 'C' from '{{.*}}/C.pcm'}}
+// CHECK: remark: importing module 'C' from '{{.*}}/C.pcm'
+#include "D.h" // \
+   expected-remark-re{{building module 'D' as '{{.*}}/D.pcm'}} \
+   expected-remark{{finished building module 'D'}} \
+   expected-remark-re{{importing module 'D' from '{{.*}}/D.pcm'}}
+// CHECK: remark: building module 'D'
+// CHECK: remark: finished building module 'D'
+// CHECK: remark: importing module 'D' from '{{.*}}/D.pcm'