Hi! On Tue, Sep 22, 2020 at 10:00:11AM +0930, Alan Modra wrote: > Power10 pc-relative code doesn't use or preserve r2 as a TOC pointer. > That means calling between pc-relative and TOC using code can't be > done without intervening linker stubs, and a call from TOC code to > pc-relative code must have a nop after the bl in order to restore r2. > > Now the PowerPC libffi assembly code doesn't use r2 except for the > implicit use when making calls back to C, ffi_closure_helper_LINUX64 > and ffi_prep_args64. So changing the assembly to interoperate with > pc-relative code without stubs is easily done. Controlling that is a > new built-in macro. > > Upstream libffi currently has a different patch applied to work around > the power10 build failure. I'll post a delta for upstream. > Bootstrapped and regression tested on power8, built for power10. > > gcc/ > * config/rs6000/rs6000-c.c (rs6000_target_modify_macros): > Conditionally define __PCREL__.
Please do that as a separate (earlier) patch (because it *is*, and to simplify backports, etc). > libffi/ > * src/powerpc/linux64.S (ffi_call_LINUX64): Don't emit global > entry when __PCREL__. Call using @notoc. > (ffi_closure_LINUX64, ffi_go_closure_linux64): Likewise. This is okay for trunk, and for backports (possibly expedited, talk with Peter for what is wanted/needed for AT). Thanks! Segher
