[Frontend/Modules] Show diagnostics on prebuilt module configuration mismatch too

The current version only emits  the below error for a module (attempted to be loaded) from the `prebuilt-module-path`:

```
error: module file blabla.pcm cannot be loaded due to a configuration mismatch with the current compilation [-Wmodule-file-config-mismatch]
```

With this change, if the prebuilt module is used, we allow the proper diagnostic behind the configuration mismatch to be shown.

```
error: POSIX thread support was disabled in PCH file but is currently enabled
error: module file blabla.pcm cannot be loaded due to a configuration mismatch with the current compilation [-Wmodule-file-config-mismatch]
```

(A few lines later an error is emitted anyways, so there is no reason not to complain for configuration mismatches if a config mismatch is found and kills the build.)

Reviewed By: dblaikie

Tags: #clang

Differential Revision: https://reviews.llvm.org/D53334

llvm-svn: 346439

1 files changed, 3 insertions, 1 deletions

diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index 719474dc765..be38c69235f 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -1727,7 +1727,9 @@ CompilerInstance::loadModule(SourceLocation ImportLoc,
     // module cache, we don't know how to rebuild modules.
     unsigned ARRFlags = Source == ModuleCache ?
                         ASTReader::ARR_OutOfDate | ASTReader::ARR_Missing :
-                        ASTReader::ARR_ConfigurationMismatch;
+                        Source == PrebuiltModulePath ?
+                            0 :
+                            ASTReader::ARR_ConfigurationMismatch;
     switch (ModuleManager->ReadAST(ModuleFileName,
                                    Source == PrebuiltModulePath
                                        ? serialization::MK_PrebuiltModule