On Wed, Dec 8, 2010 at 9:36 AM, H.J. Lu <hjl.to...@gmail.com> wrote: > On Wed, Dec 8, 2010 at 5:54 AM, H.J. Lu <hjl.to...@gmail.com> wrote: >> On Wed, Dec 8, 2010 at 1:19 AM, Andi Kleen <a...@firstfloor.org> wrote: >>>> On 12/07/2010 04:20 PM, Andi Kleen wrote: >>>>> >>>>> The only problem left is mixing of lto and non lto objects. this right >>>>> now is not handled. IMHO still the best way to handle it is to use >>>>> slim lto and then simply separate link the "left overs" after deleting >>>>> the LTO objects. This can be actually done with objcopy (with some >>>>> limitations), doesn't even need linker support. >>>>> >>>> >>>> Quite possibly a better way to deal with that is to provide a mechanism >>>> for encapsulating arbitrary binary code objects inside the LTO IR. >>> >>> Then you would need to teach your assembler and everything >> >> The magic section is generated by linker directly. No changes to >> assembler is required. >> >>> else that may generate ELF objects to generate this magic object. But why >>> not just ELF directly? that is what it is after all. >> >> My proposal isn't specific to ELF. >> >>> >>> To be honest I don't really see the point of all this complexity you >>> guys are proposing just to save fat LTO. Fat LTO is always a bad idea >>> because it's slow and does lots of redundant work. If LTO is to become >>> a more wide spread mode it has to go simply because of the poor >>> performance. >>> >>> With slim LTO passthrough is very straight-forward: simple pass >>> through every section that is not LTO and generate code for the LTO >>> sections. No new magic sections needed at all. >>> >> >> My proposal works on both fat and slim LTO objects. The idea is >> you can use "ld -r" on any combination of inputs and its output >> still works as before "ld -r". >> > > Here is the revised proposal. >
The initial implementation of my proposal is available on hjl/lto-mixed branch at http://git.kernel.org/?p=devel/binutils/hjl/x86.git;a=summary Simple case works. More cleanups are needed. Feedbacks are welcome. Thanks. -- H.J.
