On Sat, Aug 18, 2018 at 9:00 PM Iain Sandoe <i...@sandoe.co.uk> wrote:
>
> Hi
>
> While working on the Darwin LTO issues I noticed that collect2 looks for
> "-flto-partition=none” in its command line option, but it doesn’t get passed.
>
> So - is the attached patch the right idea, or should collect2 be looking in
> the COLLECT_GCC_OPTIONS as the lto-wrapper does?
Looking at COLLECT_GCC_OPTIONS is probably better.
> (or maybe it should just be just "%{fno-lto} %{flto*}" ?)
>
> I plan on making Darwin default to fno-lto for link unless there’s an “flto*”
> on the link line, since otherwise there’s a process launch for every object
> on the c/l to do “nm”, which is quite heavy weight. At present, ISTM if the
> compiler is configured with —enable-lto, the link line defaults to assuming
> that every object needs to be checked.
I think we wanted to transparently handle LTO objects (similar to how
it works with a linker plugin).
Ideally collect2 wouldn't use nm but simple-object to inspect files
(but that doesn't have symbol table query support
though looking for LTO specific sections would have been better in the
first place - I'd suggest .gnu.lto_.symtab).
Richard.
> Iain.
>
> diff --git a/gcc/gcc.c b/gcc/gcc.c
> index 780d485..bc9772b 100644
> --- a/gcc/gcc.c
> +++ b/gcc/gcc.c
> @@ -1038,7 +1038,7 @@ proper position among the other output files. */
> %(linker) " \
> LINK_PLUGIN_SPEC \
> "%{flto|flto=*:%<fcompare-debug*} \
> - %{flto} %{fno-lto} %{flto=*} %l " LINK_PIE_SPEC \
> + %{flto} %{flto-*} %{fno-lto} %{flto=*} %l " LINK_PIE_SPEC \
> "%{fuse-ld=*:-fuse-ld=%*} " LINK_COMPRESS_DEBUG_SPEC \
> "%X %{o*} %{e*} %{N} %{n} %{r}\
> %{s} %{t} %{u*} %{z} %{Z} %{!nostdlib:%{!nostartfiles:%S}} \
>
