Optionally create full debuginfo for llvm-related executables

[dim]

Summary

Commit de6feefdb7cfd limited the amount of debuginfo generated for clang
and other llvm-related executables. This was done to save disk space and
memory during building, but it makes debugging any of these executables
much harder.

Add a new src.conf(5) setting, WITH_LLVM_FULL_DEBUGINFO, to generate
full debuginfo instead. This is off by default, but could for example be
enabled for release builds or snapshots, so llvm executables are easier
to debug.

[jhb]

The original motivation was definitely that the debug info was very large. I think it was larger than all of the rest of /usr/lib/debug combined at the time. Do you have some before/after numbers now?

[dim]

Hmm... I did a test run on universe15a with MK_LLVM_LIMIT_DEBUGINFO=yes and MK_LLVM_LIMIT_DEBUG_INFO=no:

$ du -hs ~/obj/limit-*
 18G    /home/dim/obj/limit-no
5.3G    /home/dim/obj/limit-yes

and both clang and lldb have significantly larger debug info:

-rwxr-xr-x  1 dim devel  138M Feb 15 16:28 /home/dim/obj/limit-no/dim/src/freebsd/src/amd64.amd64/usr.bin/clang/clang/clang
-rwxr-xr-x  1 dim devel  1.1G Feb 15 16:28 /home/dim/obj/limit-no/dim/src/freebsd/src/amd64.amd64/usr.bin/clang/clang/clang.debug
-rwxr-xr-x  1 dim devel  138M Feb 15 15:21 /home/dim/obj/limit-yes/dim/src/freebsd/src/amd64.amd64/usr.bin/clang/clang/clang
-rwxr-xr-x  1 dim devel  370M Feb 15 15:21 /home/dim/obj/limit-yes/dim/src/freebsd/src/amd64.amd64/usr.bin/clang/clang/clang.debug

-rwxr-xr-x  1 dim devel  122M Feb 15 16:28 /home/dim/obj/limit-no/dim/src/freebsd/src/amd64.amd64/usr.bin/clang/lldb/lldb
-rwxr-xr-x  1 dim devel  1.1G Feb 15 16:28 /home/dim/obj/limit-no/dim/src/freebsd/src/amd64.amd64/usr.bin/clang/lldb/lldb.debug
-rwxr-xr-x  1 dim devel  122M Feb 15 15:21 /home/dim/obj/limit-yes/dim/src/freebsd/src/amd64.amd64/usr.bin/clang/lldb/lldb
-rwxr-xr-x  1 dim devel  353M Feb 15 15:21 /home/dim/obj/limit-yes/dim/src/freebsd/src/amd64.amd64/usr.bin/clang/lldb/lldb.debug

For other utilities the difference is less extreme:

-rwxr-xr-x  1 dim devel   79M Feb 15 16:28 /home/dim/obj/limit-no/dim/src/freebsd/src/amd64.amd64/usr.bin/clang/lld/ld.lld
-rwxr-xr-x  1 dim devel  555M Feb 15 16:28 /home/dim/obj/limit-no/dim/src/freebsd/src/amd64.amd64/usr.bin/clang/lld/ld.lld.debug
-rwxr-xr-x  1 dim devel   79M Feb 15 15:22 /home/dim/obj/limit-yes/dim/src/freebsd/src/amd64.amd64/usr.bin/clang/lld/ld.lld
-rwxr-xr-x  1 dim devel  191M Feb 15 15:22 /home/dim/obj/limit-yes/dim/src/freebsd/src/amd64.amd64/usr.bin/clang/lld/ld.lld.debug

-rwxr-xr-x  1 dim devel   19M Feb 15 16:27 /home/dim/obj/limit-no/dim/src/freebsd/src/amd64.amd64/usr.bin/clang/llvm-objdump/llvm-objdump
-rwxr-xr-x  1 dim devel   74M Feb 15 16:27 /home/dim/obj/limit-no/dim/src/freebsd/src/amd64.amd64/usr.bin/clang/llvm-objdump/llvm-objdump.debug
-rwxr-xr-x  1 dim devel   19M Feb 15 15:21 /home/dim/obj/limit-yes/dim/src/freebsd/src/amd64.amd64/usr.bin/clang/llvm-objdump/llvm-objdump
-rwxr-xr-x  1 dim devel   34M Feb 15 15:21 /home/dim/obj/limit-yes/dim/src/freebsd/src/amd64.amd64/usr.bin/clang/llvm-objdump/llvm-objdump.debug

-rwxr-xr-x  1 dim devel   17M Feb 15 16:26 /home/dim/obj/limit-no/dim/src/freebsd/src/amd64.amd64/usr.bin/clang/llvm-ar/llvm-ar
-rwxr-xr-x  1 dim devel   66M Feb 15 16:26 /home/dim/obj/limit-no/dim/src/freebsd/src/amd64.amd64/usr.bin/clang/llvm-ar/llvm-ar.debug
-rwxr-xr-x  1 dim devel   17M Feb 15 15:20 /home/dim/obj/limit-yes/dim/src/freebsd/src/amd64.amd64/usr.bin/clang/llvm-ar/llvm-ar
-rwxr-xr-x  1 dim devel   30M Feb 15 15:20 /home/dim/obj/limit-yes/dim/src/freebsd/src/amd64.amd64/usr.bin/clang/llvm-ar/llvm-ar.debug

I guess if this is enabled by default, there will be some complaints about bloat... :)

[dim]

Maybe I should start with putting LLVM_LIMIT_DEBUGINFO in __DEFAULT_YES_OPTIONS for now? Then it would not influence most people's builds at all, but it is an easy option for those that do like full debuginfo?

[jhb]

In D43839#1001891, @dim wrote:

Maybe I should start with putting LLVM_LIMIT_DEBUGINFO in __DEFAULT_YES_OPTIONS for now? Then it would not influence most people's builds at all, but it is an easy option for those that do like full debuginfo?

That seems reasonable.

[dim]

Rename option to WITH_LLVM_FULL_DEBUGINFO, off by default.