Be lazy about loading metadata in IRObjectFile.

This speeds up llvm-ar building lib64/libclangSema.a with debug IR files
from 8.658015807 seconds to just 0.351036519 seconds :-)

llvm-svn: 232221
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.h b/llvm/lib/Bitcode/Reader/BitcodeReader.h
index 0a69148..27e8b2e 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.h
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.h
@@ -255,7 +255,7 @@
   static uint64_t decodeSignRotatedValue(uint64_t V);
 
   /// Materialize any deferred Metadata block.
-  std::error_code materializeMetadata();
+  std::error_code materializeMetadata() override;
 
 private:
   std::vector<StructType *> IdentifiedStructTypes;
diff --git a/llvm/lib/IR/Module.cpp b/llvm/lib/IR/Module.cpp
index 3a88db9..3e8f91f 100644
--- a/llvm/lib/IR/Module.cpp
+++ b/llvm/lib/IR/Module.cpp
@@ -413,6 +413,12 @@
   return std::error_code();
 }
 
+std::error_code Module::materializeMetadata() {
+  if (!Materializer)
+    return std::error_code();
+  return Materializer->materializeMetadata();
+}
+
 //===----------------------------------------------------------------------===//
 // Other module related stuff.
 //
diff --git a/llvm/lib/Object/IRObjectFile.cpp b/llvm/lib/Object/IRObjectFile.cpp
index 6369d8b..58c4ca3 100644
--- a/llvm/lib/Object/IRObjectFile.cpp
+++ b/llvm/lib/Object/IRObjectFile.cpp
@@ -300,7 +300,9 @@
   std::unique_ptr<MemoryBuffer> Buff(
       MemoryBuffer::getMemBuffer(BCOrErr.get(), false));
 
-  ErrorOr<Module *> MOrErr = getLazyBitcodeModule(std::move(Buff), Context);
+  ErrorOr<Module *> MOrErr =
+      getLazyBitcodeModule(std::move(Buff), Context, nullptr,
+                           /*ShouldLazyLoadMetadata*/ true);
   if (std::error_code EC = MOrErr.getError())
     return EC;