Update LTO plugin interface

[Ian Lance Taylor]

"H.J. Lu" <hjl.tools@gmail.com> writes:

> How do you deal with -lm:

I believe we have agreed that LTO can only introduce new symbol
references that are satisfied by -lc and -lgcc.  Under those conditions,
I believe my proposal will work just fine.

Again, my proposal is this:

    I propose that we add a new linker option: --plugin-callback.  At each
    point where this option appears on the command line, the linker will
    call a new plugin callback entry point.  The LTO plugin will replace the
    all_symbols_read callback with this one.  We will have the gcc driver
    run the linker more or less like this:

    object-files -lc -lgcc --plugin-callback -lc -lgcc crtend.o crtn.o

So if the user runs something like

gcc -o foo foo.o -lm -flto

gcc will execute something like

ld crt1.o crti.o crtbegin.o foo.o -lm
   -lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc
   --plugin-callback
   -lc -lgcc --as-needed -lgcc_s --no-as-needed crtend.o crtn.o

Why would that not work?

Ian