LTO support on Mac

Hi,

I’m building LLVM on Mac OS 10.10 and I’m having trouble making LTO work. The system linker dumps the following information when I executed “ld -v”

@(#)PROGRAM:ld PROJECT:ld64-241.9
configured to support archs: armv6 armv7 armv7s arm64 i386 x86_64 x86_64h armv6m armv7m armv7em
LTO support using: LLVM version 3.4.2

which tells me that it is correctly pointing to the LLVM that I have built.

However, when I pass any LTO command line arguments like “disable-inling” it complains.

I was previously working on Linux and the gold plugin makes it very convenient. However, that plugin only handles ELF assembly and I can’t install it on Mac.

Any idea what is wrong?

I am not sure if there is a supported way of passing extra llvm
options during LTO with ld64.

Cheers,
Rafael

You can pass options with -mllvm. But you need to get it to the linker, so when invoking the linker through clang it looks like:

-Wl,-llvm,-myltoopt

That will get it to lto_codegen_debug_options(). But I don’t know what options strings lto_codegen_debug_options() handles.

-Nick

Thank you Nick. I think it’s worth giving LLD a try.
I tried building lld (branch 3.4) on top of llvm 3.4 and got the following error in the last step when it is linking lld.

[100%] Building CXX object tools/lld/tools/lld/CMakeFiles/lld.dir/lld.cpp.o
Linking CXX executable …/…/…/…/bin/lld
ld: library not found for -llldHexagonELFTarget

Can you please help me with that?

lld is a relatively new project. You should really try trunk instead of 3.4.