Register LLVM Dialect with the context. (#232)

We need to register the LLVM Dialect as a valid translation target. 
This had previously been done later in the pipeline, but since
registering dialects is not thread safe, we need to register it earlier
before we start the ThreadedCompilationManager.

Author: kitbarton

lib/API/api.cpp

@@ -55,6 +55,8 @@
 #include "mlir/Support/LLVM.h"
 #include "mlir/Support/LogicalResult.h"
 #include "mlir/Support/Timing.h"
+#include "mlir/Target/LLVMIR/Dialect/Builtin/BuiltinToLLVMIRTranslation.h"
+#include "mlir/Target/LLVMIR/Dialect/LLVMIR/LLVMToLLVMIRTranslation.h"
 #include "mlir/Tools/ParseUtilities.h"
 
 #include "llvm/ADT/StringRef.h"
@@ -432,6 +434,11 @@ llvm::Error compile_(int argc, char const **argv, std::string *outputString,
   context.allowUnregisteredDialects(config.shouldAllowUnregisteredDialects());
   context.printOpOnDiagnostic(!config.shouldVerifyDiagnostics());
 
+  // Register LLVM dialect and all infrastructure required for translation to
+  // LLVM IR
+  mlir::registerBuiltinDialectTranslation(context);
+  mlir::registerLLVMDialectTranslation(context);
+
   if (config.shouldShowDialects()) {
     showDialects_(registry);
     return llvm::Error::success();