On Fri, Dec 3, 2010 at 11:16 AM, H.J. Lu <hjl.to...@gmail.com> wrote: > On Fri, Dec 3, 2010 at 11:10 AM, Cary Coutant <ccout...@google.com> wrote: >>>>> Another way to do this would be to put a marker in the command line >>>>> that identifies where those libraries begin, and the linker could just >>>>> go back and rescan those libraries if needed, before the final layout >>>>> of the endcaps. >>>> >>>> I like that idea in general, but the difficulty is knowing where to put >>>> the marker. E.g., the user is going to specify -lm, and we are going to >>>> need to rescan it. If the user writes -lm -lmylib1 -lmylib2 we want to >>>> rescan -lm but we don't really need to rescan mylib1 and mylib2. >>> >>> All those complexities make 2 stage linking more attractive. I >>> think I can implement it in GNU linker with the current plugin API. >>> >>> Linker just needs to remember the command line options, including >>> >>> --start-group/--end-group >>> -as-needed/--no-as-needed >>> --copy-dt-needed-entries/--no-copy-dt-needed-entries >>> >>> in stage 1. >>> >>> In stage 2, it will place LTO trans files before the first IR file >>> claimed by plugin and process the command line options. >>> >>> --whole-archive may need some special handling. Archives >>> after --whole-archive will be ignored in stage 2. >> >> It seems to me that we just need to add a few more libraries as >> pass-through libraries, being careful to add a pass-through option >> only for libraries that are already on the command line. How does that >> add up to "all those complexities"? >> >> With what you've written here, you've just added to the complexity of >> your proposed solution, which makes it a much bigger change -- >> especially since what you're proposing will require changes in both >> linkers. Adding pass-through options is a gcc driver change only. >> > > I will implement 2 stage linking in GNU linker with the current plugin API. > The change shouldn't be too big. pass-through isn't needed. If we > keep it in GCC driver, my linker will simply ignore it. > > One benefit is everything will just work, with or without LTO. >
I checked the first patch into hjl/lto branch at http://git.kernel.org/?p=devel/binutils/hjl/x86.git;a=summary Now I can collect stage 2 command line. -- H.J.
