bricks: Add function that loads bitcode from file.

bricks/brick-llvm

@@ -33,11 +33,15 @@
 DIVINE_RELAX_WARNINGS
 #endif
 
+#include <llvm/IR/LLVMContext.h>
 #include <llvm/IR/Module.h>
 #include <llvm/IR/Verifier.h>
 #include <llvm/IR/Constants.h>
 #include <llvm/IR/Intrinsics.h>
 #include <llvm/Bitcode/BitcodeWriter.h>
+#include <llvm/Bitcode/BitcodeReader.h>
+#include <llvm/Object/IRObjectFile.h>
+#include <llvm/Support/MemoryBuffer.h>
 #include <llvm/Support/raw_ostream.h>
 #include <llvm/Support/raw_os_ostream.h>
 #include <llvm/Support/Error.h>
@@ -48,6 +52,8 @@ DIVINE_RELAX_WARNINGS
 DIVINE_UNRELAX_WARNINGS
 #endif
 
+#include <memory>
+
 #include <brick-assert>
 #include <brick-string>
 #include <brick-types>
@@ -244,6 +250,25 @@ inline void writeModule( ::llvm::Module *m, std::string out ) {
     WriteBitcodeToFile( *m, fs );
 }
 
+inline std::unique_ptr< ::llvm::Module > load_bc( const std::string &str,
+                                                  ::llvm::LLVMContext *ctx )
+{
+    std::unique_ptr< ::llvm::MemoryBuffer > input =
+        std::move( ::llvm::MemoryBuffer::getFile( str ).get() );
+    auto bc_input =
+        ::llvm::object::IRObjectFile::findBitcodeInMemBuffer( input->getMemBufferRef() );
+
+    if ( !bc_input )
+        UNREACHABLE( "Could not load bitcode file" );
+    auto module = ::llvm::parseBitcodeFile( bc_input.get(), *ctx );
+
+    if ( !module )
+        UNREACHABLE( "Error parsing input model; probably not a valid bc file." );
+
+    return std::move( module.get() );
+}
+
+
 inline std::string getModuleBytes( ::llvm::Module *m ) {
     std::string s;
     verifyModule( *m );