Merge remote-tracking branch 'upstream/master' into nvptx

Makefile

@@ -109,14 +109,13 @@ else
     BUILD_VERSION:=$(GIT_REVISION)
 endif
 
-CXX=g++
-CPP=cpp
+CXX=clang++
 OPT=-O2
 CXXFLAGS=$(OPT) $(LLVM_CXXFLAGS) -I. -Iobjs/ -I$(CLANG_INCLUDE)  \
 	$(LLVM_VERSION_DEF) \
 	-Wall \
 	-DBUILD_DATE="\"$(BUILD_DATE)\"" -DBUILD_VERSION="\"$(BUILD_VERSION)\"" \
-	-Wno-sign-compare
+	-Wno-sign-compare -Wno-unused-function
 ifneq ($(LLVM_VERSION),LLVM_3_1)
 	CXXFLAGS+=-Werror
 endif
@@ -202,9 +201,14 @@ ispc: print_llvm_src dirs $(OBJS)
 	$(CXX) $(OPT) $(LDFLAGS) -o $@ $(OBJS) $(ISPC_LIBS)
 
 # Use clang as a default compiler, instead of gcc
+# This is default now.
 clang: ispc
 clang: CXX=clang++
 
+# Use gcc as a default compiler, instead of gcc
+gcc: ispc
+gcc: CXX=clang++
+
 # Build ispc with address sanitizer instrumentation using clang compiler
 # Note that this is not portable build
 asan: clang