Add WITH_LLD_AS_LD build knob

If set it installs LLD as /usr/bin/ld.  LLD (as of version 3.9) is not
capable of linking the world and kernel, but can self-host and link many
substantial applications. GNU ld continues to be used for the world and
kernel build, regardless of how this knob is set.

It is on by default for arm64, and off for all other CPU architectures.

Sponsored by:	The FreeBSD Foundation

6 files changed, 17 insertions, 1 deletions

diff --git a/Makefile.inc1 b/Makefile.inc1
index b718afeef05d..8231e508a06b 100644
--- a/Makefile.inc1
+++ b/Makefile.inc1
@@ -516,7 +516,7 @@ TMAKE=		MAKEOBJDIRPREFIX=${OBJTREE} \
 # cross-tools stage
 XMAKE=		TOOLS_PREFIX=${WORLDTMP} ${BMAKE} \
 		TARGET=${TARGET} TARGET_ARCH=${TARGET_ARCH} \
-		MK_GDB=no MK_TESTS=no
+		MK_GDB=no MK_TESTS=no MK_LLD_AS_LD=no
 
 # kernel-tools stage
 KTMAKEENV=	INSTALL="sh ${.CURDIR}/tools/install.sh" \
diff --git a/gnu/usr.bin/binutils/ld/Makefile b/gnu/usr.bin/binutils/ld/Makefile
index 5bc3846a1434..6fcc69a479fc 100644
--- a/gnu/usr.bin/binutils/ld/Makefile
+++ b/gnu/usr.bin/binutils/ld/Makefile
@@ -49,7 +49,9 @@ CLEANFILES+=	ldemul-list.h stringify.sed
 
 FILES=		${LDSCRIPTS:S|^|ldscripts/|}
 FILESDIR=	${SCRIPTDIR}
+.if ${MK_LLD_AS_LD} == "no"
 LINKS=		${BINDIR}/ld.bfd ${BINDIR}/ld
+.endif
 
 HOST=		${TARGET_TUPLE}
 LIBSEARCHPATH=	\"=/lib\":\"=/usr/lib\"
diff --git a/share/mk/src.opts.mk b/share/mk/src.opts.mk
index 51b79f3d609a..655818580bd5 100644
--- a/share/mk/src.opts.mk
+++ b/share/mk/src.opts.mk
@@ -250,6 +250,11 @@ __DEFAULT_YES_OPTIONS+=LLVM_LIBUNWIND
 .else
 __DEFAULT_NO_OPTIONS+=LLVM_LIBUNWIND
 .endif
+.if ${__T} == "aarch64"
+__DEFAULT_YES_OPTIONS+=LLD_AS_LD
+.else
+__DEFAULT_NO_OPTIONS+=LLD_AS_LD
+.endif
 .if ${__T} == "aarch64" || ${__T} == "amd64"
 __DEFAULT_YES_OPTIONS+=LLD LLDB
 .else
diff --git a/tools/build/options/WITHOUT_LLD_AS_LD b/tools/build/options/WITHOUT_LLD_AS_LD
new file mode 100644
index 000000000000..0d48f205d85d
--- /dev/null
+++ b/tools/build/options/WITHOUT_LLD_AS_LD
@@ -0,0 +1,2 @@
+.\" $FreeBSD$
+Set to use GNU binutils ld as the system linker, instead of LLVM's LLD.
diff --git a/tools/build/options/WITH_LLD_AS_LD b/tools/build/options/WITH_LLD_AS_LD
new file mode 100644
index 000000000000..a291b099bf06
--- /dev/null
+++ b/tools/build/options/WITH_LLD_AS_LD
@@ -0,0 +1,2 @@
+.\" $FreeBSD$
+Set to use LLVM's LLD as the system linker, instead of GNU binutils ld.
diff --git a/usr.bin/clang/lld/Makefile b/usr.bin/clang/lld/Makefile
index ad418e35e558..65a73f2f4c0f 100644
--- a/usr.bin/clang/lld/Makefile
+++ b/usr.bin/clang/lld/Makefile
@@ -1,10 +1,15 @@
 # $FreeBSD$
 
+.include <src.opts.mk>
+
 LLVM_SRCS=	${SRCTOP}/contrib/llvm
 LLD_SRCS=	${LLVM_SRCS}/tools/lld
 
 PROG_CXX=	ld.lld
 MAN=
+.if ${MK_LLD_AS_LD} != "no"
+SYMLINKS=	${PROG_CXX} ${BINDIR}/ld
+.endif
 
 CFLAGS+=	-I${LLD_SRCS}/include
 CFLAGS+=	-I${.OBJDIR}