Update LTO plugin interface

H.J. Lu hjl.tools@gmail.com
Wed Dec 1 18:58:00 GMT 2010


On Wed, Dec 1, 2010 at 10:54 AM, Ian Lance Taylor <iant@google.com> wrote:
> "H.J. Lu" <hjl.tools@gmail.com> writes:
>
>>       b. Compiler plugin controls what linker uses to generate the final executable:
>>               i. The linker command line order should be the same, with or without LTO.
>>       c. Add a cmdline bit field to
>>       struct ld_plugin_input_file
>>       {
>>          const char *name;
>>          int fd;
>>          off_t offset;
>>          off_t filesize;
>>          void *handle;
>>          unsigned int cmdline : 1;
>>       };
>
> Just make it an int.  But I don't see why this is needed.  The plugin
> already knows the files that it passed to add_input_file and
> add_input_library.  Why does it need to linker to report back where the
> file came from?  Why doesn't the plugin just keep track?
>

It is used to keep the same linker command line order. With LTO,
linker should use

crtX.o *trans*.o -lbar -lgcc -lc ... crtX.o

instead of

crtX.o -lbar -lgcc -lc ... crtX.o  *trans*.o

to generate final executable.  2 orders may generate different
executables.

-- 
H.J.



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