Object cache: hash IR as bitcode instead of as text string

cuts down time to JIT 'pip' from 115ms to 65ms

CMakeLists.txt

@@ -93,7 +93,7 @@ endif()
 add_subdirectory(${DEPS_DIR}/llvm-trunk ${CMAKE_BINARY_DIR}/llvm EXCLUDE_FROM_ALL)
 set(CMAKE_MODULE_PATH "${CMAKE_BINARY_DIR}/llvm/share/llvm/cmake/")
 include(LLVMConfig)
-llvm_map_components_to_libnames(LLVM_LIBS core mcjit native bitreader ipo irreader debuginfodwarf instrumentation ${INTEL_JIT_EVENTS_LIB})
+llvm_map_components_to_libnames(LLVM_LIBS core mcjit native bitreader bitwriter ipo irreader debuginfodwarf instrumentation ${INTEL_JIT_EVENTS_LIB})
 
 # libunwind
 if("${CMAKE_BUILD_TYPE}" STREQUAL "Debug")

Makefile

@@ -97,7 +97,7 @@ else
 	LLVM_BIN := $(LLVM_BUILD)/Release/bin
 endif
 
-LLVM_LINK_LIBS := core mcjit native bitreader ipo irreader debuginfodwarf instrumentation
+LLVM_LINK_LIBS := core mcjit native bitreader bitwriter ipo irreader debuginfodwarf instrumentation
 ifneq ($(ENABLE_INTEL_JIT_EVENTS),0)
 LLVM_LINK_LIBS += inteljitevents
 endif

src/codegen/entry.cpp

@@ -281,7 +281,7 @@ public:
 
         // Generate a hash for the module
         HashOStream hash_stream;
-        M->print(hash_stream, 0);
+        llvm::WriteBitcodeToFile(M, hash_stream);
         hash_before_codegen = hash_stream.getHash();
 
         llvm::SmallString<128> cache_file = cache_dir;