diff --git a/gnu/lib/libgcc/Makefile b/gnu/lib/libgcc/Makefile
index 6972146dc9f2..ad4e0f1fd382 100644
--- a/gnu/lib/libgcc/Makefile
+++ b/gnu/lib/libgcc/Makefile
@@ -2,6 +2,9 @@
 
 GCCDIR=	${.CURDIR}/../../../contrib/gcc
 GCCLIB=	${.CURDIR}/../../../contrib/gcclibs
+COMPILERRTDIR=	${.CURDIR}/../../../contrib/compiler-rt
+UNWINDINCDIR=	${.CURDIR}/../../../contrib/llvm/projects/libunwind/include
+UNWINDSRCDIR=	${.CURDIR}/../../../contrib/llvm/projects/libunwind/src
 
 SHLIB_NAME=	libgcc_s.so.1
 SHLIBDIR?=	/lib
@@ -67,8 +70,37 @@ LIB2ADD = $(LIB2FUNCS_EXTRA)
 LIB2ADD_ST = $(LIB2FUNCS_STATIC_EXTRA)
 
 # Additional sources to handle exceptions; overridden by targets as needed.
+.if ${MK_LLVM_LIBUNWIND} != "no"
+
+.PATH: ${COMPILERRTDIR}/lib/builtins
+.PATH: ${UNWINDSRCDIR}
+LIB2ADDEH = gcc_personality_v0.c \
+	int_util.c \
+	Unwind-EHABI.cpp \
+	Unwind-sjlj.c \
+	UnwindLevel1-gcc-ext.c \
+	UnwindLevel1.c \
+	UnwindRegistersRestore.S \
+	UnwindRegistersSave.S \
+	libunwind.cpp
+
+CFLAGS+=	-I${UNWINDINCDIR} -I${.CURDIR}
+.if empty(CXXFLAGS:M-std=*)
+CXXFLAGS+=	-std=c++11
+.endif
+CXXFLAGS+=	-fno-rtti
+
+.else # MK_LLVM_LIBUNWIND
+
+.if ${TARGET_CPUARCH} == "arm"
+LIB2ADDEH =	unwind-arm.c libunwind.S pr-support.c unwind-c.c
+.else
 LIB2ADDEH = unwind-dw2.c unwind-dw2-fde-glibc.c unwind-sjlj.c gthr-gnat.c \
 	unwind-c.c
+.endif
+
+.endif # MK_LLVM_LIBUNWIND
+
 LIB2ADDEHSTATIC = $(LIB2ADDEH)
 LIB2ADDEHSHARED = $(LIB2ADDEH)
 
@@ -116,7 +148,6 @@ CFLAGS.clang+=	-fheinous-gnu-extensions
 
 LIB1ASMSRC =	lib1funcs.asm
 LIB1ASMFUNCS =  _dvmd_tls _bb_init_func
-LIB2ADDEH =	unwind-arm.c libunwind.S pr-support.c unwind-c.c
 # Some compilers generate __aeabi_ functions libgcc_s is missing
 LIBADD+=	compiler_rt
 .endif
@@ -160,7 +191,10 @@ LIB2_DIVMOD_FUNCS:= ${LIB2_DIVMOD_FUNCS:S/${sym}//g}
 .endfor
 .endif
 
-COMMONHDRS=	tm.h tconfig.h options.h unwind.h gthr-default.h
+COMMONHDRS=	tm.h tconfig.h options.h gthr-default.h
+.if ${MK_LLVM_LIBUNWIND} == no
+COMMONHDRS+=	unwind.h
+.endif
 
 #-----------------------------------------------------------------------
 #
@@ -170,6 +204,9 @@ HIDE =  -fvisibility=hidden -DHIDE_EXPORTS
 CC_T =	${CC} -c ${CFLAGS} ${HIDE} -fPIC
 CC_P =	${CC} -c ${CFLAGS} ${HIDE} -p -fPIC
 CC_S =	${CC} -c ${CFLAGS} ${PICFLAG} -DSHARED
+CXX_T =	${CXX} -c ${CXXFLAGS} ${HIDE} -fPIC
+CXX_P =	${CXX} -c ${CXXFLAGS} ${HIDE} -p -fPIC
+CXX_S =	${CXX} -c ${CXXFLAGS} ${PICFLAG} -DSHARED
 
 #-----------------------------------------------------------------------
 #
@@ -284,16 +321,26 @@ EH_OBJS_S = ${LIB2ADDEHSHARED:R:S/$/.So/}
 EH_CFLAGS = -fexceptions -D__GLIBC__=3 -DElfW=__ElfN
 SOBJS    += ${EH_OBJS_S}
 
-.for _src in ${LIB2ADDEHSTATIC}
+.for _src in ${LIB2ADDEHSTATIC:M*.c}
 ${_src:R:S/$/.o/}: ${_src} ${COMMONHDRS}
 	${CC_T} ${EH_CFLAGS} -o ${.TARGET} ${.IMPSRC}
 ${_src:R:S/$/.po/}: ${_src} ${COMMONHDRS}
 	${CC_P} ${EH_CFLAGS} -o ${.TARGET} ${.IMPSRC}
 .endfor
-.for _src in ${LIB2ADDEHSHARED}
+.for _src in ${LIB2ADDEHSTATIC:M*.cpp}
+${_src:R:S/$/.o/}: ${_src} ${COMMONHDRS}
+	${CXX_T} ${EH_CFLAGS} -o ${.TARGET} ${.IMPSRC}
+${_src:R:S/$/.po/}: ${_src} ${COMMONHDRS}
+	${CXX_P} ${EH_CFLAGS} -o ${.TARGET} ${.IMPSRC}
+.endfor
+.for _src in ${LIB2ADDEHSHARED:M*.c}
 ${_src:R:S/$/.So/}: ${_src} ${COMMONHDRS}
 	${CC_S} ${EH_CFLAGS} -o ${.TARGET} ${.IMPSRC}
 .endfor
+.for _src in ${LIB2ADDEHSHARED:M*.cpp}
+${_src:R:S/$/.So/}: ${_src} ${COMMONHDRS}
+	${CXX_S} ${EH_CFLAGS} -o ${.TARGET} ${.IMPSRC}
+.endfor
 
 
 #-----------------------------------------------------------------------
diff --git a/share/mk/src.opts.mk b/share/mk/src.opts.mk
index 47a67e02e52a..678c31ef054b 100644
--- a/share/mk/src.opts.mk
+++ b/share/mk/src.opts.mk
@@ -231,9 +231,9 @@ __DEFAULT_NO_OPTIONS+=CLANG CLANG_BOOTSTRAP CLANG_FULL CLANG_IS_CC
 # In-tree binutils/gcc are older versions without modern architecture support.
 .if ${__T} == "aarch64" || ${__T} == "riscv64"
 BROKEN_OPTIONS+=BINUTILS BINUTILS_BOOTSTRAP GCC GCC_BOOTSTRAP GDB
-__DEFAULT_YES_OPTIONS+=ELFCOPY_AS_OBJCOPY
+__DEFAULT_YES_OPTIONS+=ELFCOPY_AS_OBJCOPY LLVM_LIBUNWIND
 .else
-__DEFAULT_NO_OPTIONS+=ELFCOPY_AS_OBJCOPY
+__DEFAULT_NO_OPTIONS+=ELFCOPY_AS_OBJCOPY LLVM_LIBUNWIND
 .endif
 .if ${__T} == "riscv64"
 BROKEN_OPTIONS+=PROFILE # "sorry, unimplemented: profiler support for RISC-V"
diff --git a/tools/build/options/WITHOUT_LLVM_LIBUNWIND b/tools/build/options/WITHOUT_LLVM_LIBUNWIND
new file mode 100644
index 000000000000..63a904230a26
--- /dev/null
+++ b/tools/build/options/WITHOUT_LLVM_LIBUNWIND
@@ -0,0 +1,2 @@
+.\" $FreeBSD$
+Set to use GCC's stack unwinder (instead of LLVM's libunwind).
diff --git a/tools/build/options/WITH_LLVM_LIBUNWIND b/tools/build/options/WITH_LLVM_LIBUNWIND
new file mode 100644
index 000000000000..ff63884af9e4
--- /dev/null
+++ b/tools/build/options/WITH_LLVM_LIBUNWIND
@@ -0,0 +1,2 @@
+.\" $FreeBSD$
+Set to use LLVM's libunwind stack unwinder (instead of GCC's unwinder).