Subzero: Build with function/data sections and -gc-sections.

Makefile.standalone

 # The following variables will likely need to be modified, depending on where
 # and how you built LLVM & Clang. They can be overridden in a command-line
 # invocation of make, like:
 #
 #   make LLVM_SRC_PATH=<path> LLVM_BIN_PATH=<path> \
 #        LIBCXX_INSTALL_PATH=<path> CLANG_PATH=<path> ...
 #
 
 # LLVM_SRC_PATH is the path to the root of the checked out source code. This
 # directory should contain the configure script, the include/ and lib/
@@ skipping 24 matching lines @@
   ifeq ($(HOST_ARCH),x86)
     HOST_FLAGS = -m32 -stdlib=libc++
   endif
 endif
 
 ifdef DEBUG
   OBJDIR = build/Debug
   OPTLEVEL = -O0
 else
   OBJDIR = build/Release
-  OPTLEVEL = -O2
+  OPTLEVEL = -O2 -ffunction-sections -fdata-sections
 endif
 
 # The list of CXX defines that are dependent on build parameters.
 CXX_DEFINES =
 
 ifdef MINIMAL
   NOASSERT = 1
   OBJDIR := $(OBJDIR)+Min
   CXX_DEFINES += -DALLOW_DUMP=0 -DALLOW_LLVM_CL=0 -DALLOW_LLVM_IR=0 \
         -DALLOW_LLVM_IR_AS_INPUT=0 -DALLOW_DISABLE_IR_GEN=0
@@ skipping 23 matching lines @@
                 `$(LLVM_BIN_PATH)/llvm-config --system-libs`
 
 # It's recommended that CXX matches the compiler you used to build LLVM itself.
 CCACHE := `command -v ccache`
 CXX := CCACHE_CPP2=yes $(CCACHE) $(CLANG_PATH)/clang++
 
 CXXFLAGS := $(LLVM_CXXFLAGS) -std=c++11 -Wall -Wextra -Werror -fno-rtti \
         -fno-exceptions $(OPTLEVEL) $(ASSERTIONS) $(CXX_DEFINES) -g \
         $(HOST_FLAGS) -Wno-error=unused-parameter \
         -I$(LIBCXX_INSTALL_PATH)/include/c++/v1
-LDFLAGS := $(HOST_FLAGS) -L$(LIBCXX_INSTALL_PATH)/lib
+LDFLAGS := $(HOST_FLAGS) -L$(LIBCXX_INSTALL_PATH)/lib -Wl,--gc-sections
 
 SRCS = \
         assembler.cpp \
         assembler_ia32.cpp \
         IceCfg.cpp \
         IceCfgNode.cpp \
         IceELFObjectWriter.cpp \
         IceELFSection.cpp \
         IceGlobalContext.cpp \
         IceGlobalInits.cpp \
@@ skipping 102 matching lines @@
 endif
 format-diff:
         git diff -U0 `git merge-base HEAD master` | \
         $(CLANG_FORMAT_DIFF) -p1 -style=LLVM -i
 
 clean:
         rm -rf llvm2ice *.o $(OBJDIR)
 
 clean-all: clean
         rm -rf build/