1 files changed, 32 insertions, 4 deletions
diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index 04a4c7dbe68..c02eb761041 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -712,15 +712,18 @@ std::unique_ptr<llvm::raw_pwrite_stream> CompilerInstance::createOutputFile(
 // Initialization Utilities
 
 bool CompilerInstance::InitializeSourceManager(const FrontendInputFile &Input){
-  return InitializeSourceManager(Input, getDiagnostics(),
-                                 getFileManager(), getSourceManager(), 
-                                 getFrontendOpts());
+  return InitializeSourceManager(
+      Input, getDiagnostics(), getFileManager(), getSourceManager(),
+      hasPreprocessor() ? &getPreprocessor().getHeaderSearchInfo() : nullptr,
+      getFrontendOpts());
 }
 
+// static
 bool CompilerInstance::InitializeSourceManager(const FrontendInputFile &Input,
                                                DiagnosticsEngine &Diags,
                                                FileManager &FileMgr,
                                                SourceManager &SourceMgr,
+                                               HeaderSearch *HS,
                                                const FrontendOptions &Opts) {
   SrcMgr::CharacteristicKind
     Kind = Input.isSystem() ? SrcMgr::C_System : SrcMgr::C_User;
@@ -737,7 +740,32 @@ bool CompilerInstance::InitializeSourceManager(const FrontendInputFile &Input,
 
   // Figure out where to get and map in the main file.
   if (InputFile != "-") {
-    const FileEntry *File = FileMgr.getFile(InputFile, /*OpenFile=*/true);
+    const FileEntry *File;
+    if (Opts.FindPchSource.empty()) {
+      File = FileMgr.getFile(InputFile, /*OpenFile=*/true);
+    } else {
+      // When building a pch file in clang-cl mode, the .h file is built as if
+      // it was included by a cc file.  Since the driver doesn't know about
+      // all include search directories, the frontend must search the input
+      // file through HeaderSearch here, as if it had been included by the
+      // cc file at Opts.FindPchSource.
+      const FileEntry *FindFile = FileMgr.getFile(Opts.FindPchSource);
+      if (!FindFile) {
+        Diags.Report(diag::err_fe_error_reading) << Opts.FindPchSource;
+        return false;
+      }
+      const DirectoryLookup *UnusedCurDir;
+      SmallVector<std::pair<const FileEntry *, const DirectoryEntry *>, 16>
+          Includers;
+      Includers.push_back(std::make_pair(FindFile, FindFile->getDir()));
+      File = HS->LookupFile(InputFile, SourceLocation(), /*isAngled=*/false,
+                            /*FromDir=*/nullptr,
+                            /*CurDir=*/UnusedCurDir, Includers,
+                            /*SearchPath=*/nullptr,
+                            /*RelativePath=*/nullptr,
+                            /*RequestingModule=*/nullptr,
+                            /*SuggestedModule=*/nullptr, /*SkipCache=*/true);
+    }
     if (!File) {
       Diags.Report(diag::err_fe_error_reading) << InputFile;
       return false;