Index: clang-tools-extra/clangd/index/SymbolCollector.cpp
===================================================================
--- clang-tools-extra/clangd/index/SymbolCollector.cpp
+++ clang-tools-extra/clangd/index/SymbolCollector.cpp
@@ -687,8 +687,10 @@
 
   const auto &SM = PP->getSourceManager();
   auto DefLoc = MI->getDefinitionLoc();
-  // Also avoid storing predefined macros like __DBL_MIN__.
+  // Also avoid storing macros that aren't defined in any file, i.e. predefined
+  // macros like __DBL_MIN__ and those defined on the command line.
   if (SM.isWrittenInBuiltinFile(DefLoc) ||
+      SM.isWrittenInCommandLineFile(DefLoc) ||
       Name->getName() == "__GCC_HAVE_DWARF2_CFI_ASM")
     return true;
 
Index: clang/lib/Serialization/ASTReader.cpp
===================================================================
--- clang/lib/Serialization/ASTReader.cpp
+++ clang/lib/Serialization/ASTReader.cpp
@@ -654,6 +654,10 @@
   SmallVector<StringRef, 4> ExistingMacroNames;
   collectMacroDefinitions(ExistingPPOpts, ExistingMacros, &ExistingMacroNames);
 
+  // Use a line marker to enter the <command line> file, as the defines and
+  // undefines here will have come from the command line.
+  SuggestedPredefines += "# 1 \"<command line>\" 1\n";
+
   for (unsigned I = 0, N = ExistingMacroNames.size(); I != N; ++I) {
     // Dig out the macro definition in the existing preprocessor options.
     StringRef MacroName = ExistingMacroNames[I];
@@ -713,6 +717,10 @@
     }
     return true;
   }
+
+  // Leave the <command line> file and return to <built-in>.
+  SuggestedPredefines += "# 1 \"<built-in>\" 2\n";
+
   if (Validation == OptionValidateStrictMatches) {
     // If strict matches are requested, don't tolerate any extra defines in
     // the AST file that are missing on the command line.
@@ -1579,8 +1587,13 @@
     auto Buffer = ReadBuffer(SLocEntryCursor, Name);
     if (!Buffer)
       return true;
-    SourceMgr.createFileID(std::move(Buffer), FileCharacter, ID,
-                           BaseOffset + Offset, IncludeLoc);
+    FileID FID = SourceMgr.createFileID(std::move(Buffer), FileCharacter, ID,
+                                        BaseOffset + Offset, IncludeLoc);
+    if (Record[3]) {
+      SrcMgr::FileInfo &FileInfo =
+          const_cast<SrcMgr::FileInfo &>(SourceMgr.getSLocEntry(FID).getFile());
+      FileInfo.setHasLineDirectives();
+    }
     break;
   }
 
Index: clang/lib/Serialization/ASTWriter.cpp
===================================================================
--- clang/lib/Serialization/ASTWriter.cpp
+++ clang/lib/Serialization/ASTWriter.cpp
@@ -4444,6 +4444,11 @@
 bool ASTWriter::PreparePathForOutput(SmallVectorImpl<char> &Path) {
   assert(Context && "should have context when outputting path");
 
+  // Leave special file names as they are.
+  StringRef PathStr(Path.data(), Path.size());
+  if (PathStr == "<built-in>" || PathStr == "<command line>")
+    return false;
+
   bool Changed =
       cleanPathForOutput(Context->getSourceManager().getFileManager(), Path);
 
Index: clang/test/PCH/macro-cmdline.c
===================================================================
--- /dev/null
+++ clang/test/PCH/macro-cmdline.c
@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 %s -emit-pch -o %t1.pch -DMACRO1=1
+// RUN: %clang_cc1 -fsyntax-only %s -include-pch %t1.pch -DMACRO2=1 2>&1 | FileCheck %s
+
+#ifndef HEADER
+#define HEADER
+#else
+#define MACRO1 2
+// CHECK: macro-cmdline.c{{.*}}'MACRO1' macro redefined
+// CHECK: <command line>{{.*}}previous definition is here
+#define MACRO2 2
+// CHECK: macro-cmdline.c{{.*}}'MACRO2' macro redefined
+// CHECK: <command line>{{.*}}previous definition is here
+#endif
Index: clang/test/PCH/ms-pch-macro.c
===================================================================
--- clang/test/PCH/ms-pch-macro.c
+++ clang/test/PCH/ms-pch-macro.c
@@ -36,4 +36,4 @@
 // CHECK-FOO: definition of macro 'FOO' differs between the precompiled header ('1') and the command line ('blah')
 // CHECK-NOFOO: macro 'FOO' was defined in the precompiled header but undef'd on the command line
 
-// expected-warning@1 {{definition of macro 'BAR' does not match definition in precompiled header}}
+// expected-warning@2 {{definition of macro 'BAR' does not match definition in precompiled header}}