diff --git a/Makefile.in b/Makefile.in
index e7d5650a881df..149f41222319d 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -212,7 +212,9 @@ LLVM_INCDIR_$(1)=$$(shell "$$(LLVM_CONFIG_$(1))" --includedir)
 LLVM_LIBDIR_$(1)=$$(shell "$$(LLVM_CONFIG_$(1))" --libdir)
 LLVM_LIBS_$(1)=$$(shell "$$(LLVM_CONFIG_$(1))" --libs $$(LLVM_COMPONENTS))
 LLVM_LDFLAGS_$(1)=$$(shell "$$(LLVM_CONFIG_$(1))" --ldflags)
-LLVM_CXXFLAGS_$(1)=$$(shell "$$(LLVM_CONFIG_$(1))" --cxxflags)
+# On FreeBSD, it may search wrong headers (that are for pre-installed LLVM),
+# so we replace -I with -iquote to ensure that it searches bundled LLVM first.
+LLVM_CXXFLAGS_$(1)=$$(subst -I, -iquote , $$(shell "$$(LLVM_CONFIG_$(1))" --cxxflags))
 LLVM_HOST_TRIPLE_$(1)=$$(shell "$$(LLVM_CONFIG_$(1))" --host-target)
 
 LLVM_AS_$(1)=$$(CFG_LLVM_INST_DIR_$(1))/bin/llvm-as$$(X)
diff --git a/configure b/configure
index 1601f46ac1e56..b769b529b8ac9 100755
--- a/configure
+++ b/configure
@@ -536,14 +536,25 @@ do
 	# Disable unused LLVM features
 	LLVM_OPTS="$LLVM_DBG_OPTS --disable-docs --disable-jit --enable-bindings=none --disable-threads --disable-pthreads"
 
-	LLVM_CXX_32="g++ -m32"
-	LLVM_CC_32="gcc -m32"
+	if [ "$CFG_C_COMPILER" = "clang" ]
+	then
+	    LLVM_CXX_32="clang++ -m32"
+	    LLVM_CC_32="clang -m32"
+
+	    LLVM_CXX_64="clang++"
+	    LLVM_CC_64="clang"
+	else
+	    LLVM_CXX_32="g++ -m32"
+	    LLVM_CC_32="gcc -m32"
+
+	    LLVM_CXX_64="g++"
+	    LLVM_CC_64="gcc"
+	fi
+
 	LLVM_CFLAGS_32="-m32"
 	LLVM_CXXFLAGS_32="-m32"
 	LLVM_LDFLAGS_32="-m32"
 
-	LLVM_CXX_64="g++"
-	LLVM_CC_64="gcc"
 	LLVM_CFLAGS_64=""
 	LLVM_CXXFLAGS_64=""
 	LLVM_LDFLAGS_64=""