Don't crash if an error is emitted by Clang IR-generation.

Clang IR-generation can fail.  When it does this, it destroys the
module. Previously, we were blithely assuming this couldn't happen,
and so we would crash on the deallocated module.  Delay the
finalization of the Clang code generator until our own module
finalization, which is a more appropriate place for it anyway,
and then just bail out of the last few steps if Clang fails.

Author: rjmccall

lib/IRGen/GenDecl.cpp

@@ -843,10 +843,6 @@ void IRGenModule::finishEmitAfterTopLevel() {
   for (auto def : Context.ExternalDefinitions) {
     emitExternalDefinition(def);
   }
-
-  // Let ClangCodeGen emit its global data structures (llvm.used, debug info,
-  // etc.)
-  finalizeClangCodeGen();
 }
 
 static void emitLazyTypeMetadata(IRGenModule &IGM, CanType type) {

lib/IRGen/IRGen.cpp

@@ -628,7 +628,8 @@ static std::unique_ptr<llvm::Module> performIRGeneration(IRGenOptions &Opts,
       });
     }
 
-    IGM.finalize();
+    if (!IGM.finalize())
+      return nullptr;
 
     setModuleFlags(IGM);
   }
@@ -821,7 +822,9 @@ static void performParallelIRGeneration(IRGenOptions &Opts,
       updateLinkage(F);
     }
 
-    IGM->finalize();
+    if (!IGM->finalize())
+      return;
+
     setModuleFlags(*IGM);
   }
 

lib/IRGen/IRGenModule.cpp

@@ -969,7 +969,7 @@ void IRGenModule::cleanupClangCodeGenMetadata() {
                          (uint32_t)(swiftVersion << 8));
 }
 
-void IRGenModule::finalize() {
+bool IRGenModule::finalize() {
   const char *ModuleHashVarName = "llvm.swift_module_hash";
   if (IRGen.Opts.OutputKind == IRGenOutputKind::ObjectFile &&
       !Module.getGlobalVariable(ModuleHashVarName)) {
@@ -1000,11 +1000,21 @@ void IRGenModule::finalize() {
     addUsedGlobal(ModuleHash);
   }
   emitLazyPrivateDefinitions();
+
+  // Finalize clang IR-generation.
+  finalizeClangCodeGen();
+
+  // If that failed, report failure up and skip the final clean-up.
+  if (!ClangCodeGen->GetModule())
+    return false;
+
   emitAutolinkInfo();
   emitGlobalLists();
   if (DebugInfo)
     DebugInfo->finalize();
   cleanupClangCodeGenMetadata();
+
+  return true;
 }
 
 /// Emit lazy definitions that have to be emitted in this specific

lib/IRGen/IRGenModule.h

@@ -787,7 +787,12 @@ private:                            \
 
   void emitSourceFile(SourceFile &SF, unsigned StartElem);
   void addLinkLibrary(const LinkLibrary &linkLib);
-  void finalize();
+
+  /// Attempt to finalize the module.
+  ///
+  /// This can fail, in which it will return false and the module will be
+  /// invalid.
+  bool finalize();
 
   llvm::AttributeSet constructInitialAttributes();
 

test/IRGen/Inputs/c_functions_error.h

@@ -0,0 +1,6 @@
+static inline void produce_error_in_clang_irgen() {
+  typedef double __m128d __attribute__((__vector_size__(16)));
+
+  __m128d a, b;
+  __builtin_ia32_addsubps(b, a);
+}

test/IRGen/c_functions_error.swift

@@ -0,0 +1,9 @@
+// RUN: not %target-swift-frontend -Xcc -mno-sse -import-objc-header %S/Inputs/c_functions_error.h -primary-file %s -emit-ir
+
+// This should fail, but not crash.
+
+// REQUIRES: CPU=x86_64
+
+func call_buggy_builtin() {
+  produce_error_in_clang_irgen();
+}