Enabling the gold linker on Freebsd

Question

I have been trying to enable the gold linker on FreeBSD to use the link time optimizations. I made gold from the binutils under /usr/ports. After building binutils using make -k install clean i got ld under /usr/bin and in the directory /usr/local/bin i got ld, ld.gold and ld.bfd.

Now while trying to use link time optimization for the simple example programs here http://llvm.org/docs/GoldPlugin.html (a.c and b.c under the heading 'Examples of Link Time Optimization') i entered the four commands as follows:

clang -flto a.c -c -o a.o 
ar q a.a a.o 
clang b.c -c -o b.o 
clang -flto a.a b.o -o main

I got the following error:

usr/bin/ld: unrecogonized option '-plugin'
usr/bin/ld: use the --help option for usage information
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Is there the problem with the linker that ld.gold is not being called. Should I replace the ld with ld.gold? Does the linker looks in the right directiry for the .so plugins?

The LLVMgold.so and libLTO.so shared objects are in the directory /usr/local/llvm-devel/lib/. I cannot find the directory where clang is installed. I am not sure where to make the bfd-plugins directory and add the symlinks to LLVMgold.so and libLTO.so.

I am using freebsd 10.1 release. How to enable the gold linker for link time optimizations? also how can I enable it to be the default linker?

Answer 1

I'm not sure ld.bfd allows plugins, but I could be wrong.

Your /usr/bin/ld should be a symlink to whatever linker you want. You can change which linker is used by using binutils-config. Check the man-page here: http://www.linuxhowtos.org/manpages/8/binutils-config.htm. I realise this is a Linux link, but it's directed at binutils itself rather than linux-specifically.

It should be something along the lines binutils-config --gold. On my Gentoo box it is binutils --linker=gold

EDIT: As pointed out, binutils-config doesn't work on BSD it seems. You can still manually update the symlinks though, the downside is that there might be a few of them. You can find out which ld is used by your compiler by using gcc -print-prog-name=ld or clang -print-prog-name=ld. The file printed should be a symlink you can re-create to point to ld.gold as oposed to ld.bfd.

Answer 2

You may want to use ld.gold instead of ld. It is installed at /usr/local/bin/ld.gold. If you are using a Makefile, it would work by setting LD variable to ld.gold, either by modifying your Makefile or specifying it on command line. Example in case you are using lang/clang37:

gmake all CC=clang37 LD=ld.gold

EDIT:

It would be even more neat if you add -fuse-ld=gold to your LDFLAGS:

LDFLAGS=-fuse-ld=gold