diff --git a/clang/include/clang/Frontend/CompilerInstance.h b/clang/include/clang/Frontend/CompilerInstance.h
--- a/clang/include/clang/Frontend/CompilerInstance.h
+++ b/clang/include/clang/Frontend/CompilerInstance.h
@@ -150,7 +150,7 @@
   bool HaveFullGlobalModuleIndex = false;
 
   /// One or more modules failed to build.
-  bool ModuleBuildFailed = false;
+  bool DisableGeneratingGlobalModuleIndex = false;
 
   /// The stream for verbose output if owned, otherwise nullptr.
   std::unique_ptr<raw_ostream> OwnedVerboseOutputStream;
diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -77,7 +77,7 @@
   return (BuildGlobalModuleIndex ||
           (TheASTReader && TheASTReader->isGlobalIndexUnavailable() &&
            getFrontendOpts().GenerateGlobalModuleIndex)) &&
-         !ModuleBuildFailed;
+         !DisableGeneratingGlobalModuleIndex;
 }
 
 void CompilerInstance::setDiagnostics(DiagnosticsEngine *Value) {
@@ -1683,7 +1683,7 @@
     // We can't find a module, error out here.
     getDiagnostics().Report(ModuleNameLoc, diag::err_module_not_found)
         << ModuleName << SourceRange(ImportLoc, ModuleNameLoc);
-    ModuleBuildFailed = true;
+    DisableGeneratingGlobalModuleIndex = true;
     return nullptr;
   }
   if (ModuleFilename.empty()) {
@@ -1695,7 +1695,7 @@
 
     getDiagnostics().Report(ModuleNameLoc, diag::err_module_build_disabled)
         << ModuleName;
-    ModuleBuildFailed = true;
+    DisableGeneratingGlobalModuleIndex = true;
     return nullptr;
   }
 
@@ -1742,7 +1742,7 @@
         if (*ModuleFile == M->getASTFile())
           return M;
 
-    ModuleBuildFailed = true;
+    DisableGeneratingGlobalModuleIndex = true;
     getDiagnostics().Report(ModuleNameLoc, diag::err_module_prebuilt)
         << ModuleName;
     return ModuleLoadResult();
@@ -1764,14 +1764,14 @@
     LLVM_FALLTHROUGH;
   case ASTReader::VersionMismatch:
   case ASTReader::HadErrors:
-    // FIXME: Should this set ModuleBuildFailed = true?
+    // FIXME: Should this set DisableGeneratingGlobalModuleIndex = true?
     ModuleLoader::HadFatalFailure = true;
     // FIXME: The ASTReader will already have complained, but can we shoehorn
     // that diagnostic information into a more useful form?
     return ModuleLoadResult();
 
   case ASTReader::Failure:
-    // FIXME: Should this set ModuleBuildFailed = true?
+    // FIXME: Should this set DisableGeneratingGlobalModuleIndex = true?
     ModuleLoader::HadFatalFailure = true;
     return ModuleLoadResult();
   }
@@ -1781,7 +1781,7 @@
     // We don't know the desired configuration for this module and don't
     // necessarily even have a module map. Since ReadAST already produces
     // diagnostics for these two cases, we simply error out here.
-    ModuleBuildFailed = true;
+    DisableGeneratingGlobalModuleIndex = true;
     return ModuleLoadResult();
   }
 
@@ -1806,7 +1806,7 @@
 
     getDiagnostics().Report(ModuleNameLoc, diag::err_module_cycle)
         << ModuleName << CyclePath;
-    // FIXME: Should this set ModuleBuildFailed = true?
+    // FIXME: Should this set DisableGeneratingGlobalModuleIndex = true?
     return nullptr;
   }
 
@@ -1816,7 +1816,7 @@
       getPreprocessorOpts().FailedModules->hasAlreadyFailed(ModuleName)) {
     getDiagnostics().Report(ModuleNameLoc, diag::err_module_not_built)
         << ModuleName << SourceRange(ImportLoc, ModuleNameLoc);
-    ModuleBuildFailed = true;
+    DisableGeneratingGlobalModuleIndex = true;
     return nullptr;
   }
 
@@ -1827,7 +1827,7 @@
            "undiagnosed error in compileModuleAndReadAST");
     if (getPreprocessorOpts().FailedModules)
       getPreprocessorOpts().FailedModules->addFailed(ModuleName);
-    ModuleBuildFailed = true;
+    DisableGeneratingGlobalModuleIndex = true;
     return nullptr;
   }
 
@@ -1871,16 +1871,16 @@
     //if (Module == nullptr) {
     //  getDiagnostics().Report(ModuleNameLoc, diag::err_module_not_found)
     //    << ModuleName;
-    //  ModuleBuildFailed = true;
+    //  DisableGeneratingGlobalModuleIndex = true;
     //  return ModuleLoadResult();
     //}
     MM.cacheModuleLoad(*Path[0].first, Module);
   } else {
     ModuleLoadResult Result = findOrCompileModuleAndReadAST(
         ModuleName, ImportLoc, ModuleNameLoc, IsInclusionDirective);
-    // FIXME: Can we pull 'ModuleBuildFailed = true' out of the return
-    // sequences for findOrCompileModuleAndReadAST and do it here (as long as
-    // the result is not a config mismatch)?  See FIXMEs there.
+    // FIXME: Can we pull 'DisableGeneratingGlobalModuleIndex = true' out of
+    // the return sequences for findOrCompileModuleAndReadAST and do it here
+    // (as long as the result is not a config mismatch)?  See FIXMEs there.
     if (!Result.isNormal())
       return Result;
     Module = Result;