[IRReader] Expose getLazyIRModule

Currently there is no way to lazy-load an in-memory IR module without
first writing it to disk. This patch just exposes the existing
implementation of getLazyIRModule.

This is effectively a revert of rL212364

Differential Revision: https://reviews.llvm.org/D56203

llvm-svn: 353755

include/llvm/IRReader/IRReader.h

@@ -20,11 +20,22 @@
 namespace llvm {
 
 class StringRef;
+class MemoryBuffer;
 class MemoryBufferRef;
 class Module;
 class SMDiagnostic;
 class LLVMContext;
 
+/// If the given MemoryBuffer holds a bitcode image, return a Module
+/// for it which does lazy deserialization of function bodies.  Otherwise,
+/// attempt to parse it as LLVM Assembly and return a fully populated
+/// Module. The ShouldLazyLoadMetadata flag is passed down to the bitcode
+/// reader to optionally enable lazy metadata loading. This takes ownership
+/// of \p Buffer.
+std::unique_ptr<Module> getLazyIRModule(std::unique_ptr<MemoryBuffer> Buffer,
+                                        SMDiagnostic &Err, LLVMContext &Context,
+                                        bool ShouldLazyLoadMetadata = false);
+
 /// If the given file holds a bitcode image, return a Module
 /// for it which does lazy deserialization of function bodies.  Otherwise,
 /// attempt to parse it as LLVM Assembly and return a fully populated

lib/IRReader/IRReader.cpp

@@ -29,9 +29,9 @@ static const char *const TimeIRParsingGroupDescription = "LLVM IR Parsing";
 static const char *const TimeIRParsingName = "parse";
 static const char *const TimeIRParsingDescription = "Parse IR";
 
-static std::unique_ptr<Module>
-getLazyIRModule(std::unique_ptr<MemoryBuffer> Buffer, SMDiagnostic &Err,
-                LLVMContext &Context, bool ShouldLazyLoadMetadata) {
+std::unique_ptr<Module>
+llvm::getLazyIRModule(std::unique_ptr<MemoryBuffer> Buffer, SMDiagnostic &Err,
+                      LLVMContext &Context, bool ShouldLazyLoadMetadata) {
   if (isBitcode((const unsigned char *)Buffer->getBufferStart(),
                 (const unsigned char *)Buffer->getBufferEnd())) {
     Expected<std::unique_ptr<Module>> ModuleOrErr = getOwningLazyBitcodeModule(