http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48220
--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-03-23 16:45:05 UTC --- The aim of the extension is to allow correct debug info, not almost correct, so I think defining "upon entering of the current subprogram" as anything but before the first insn in it is wrong and would make it not possible to use DW_OP_GNU_entry_value before the point (end of prologue or what?). Consider e.g. shrink-wrapping Bernd just proposed for GCC too... So I think what we currently do on SPARC has to change. As for teaching var-tracking about save/restore on SPARC, it would be a matter of adding probably two target hooks, one that would be run e.g. at the end of adjust_insn and would be supposed to change it using validate_change (..., true); in whatever way var-tracking should understand the insn. So e.g. for save you'd add into the parallel things like: (set (reg:P 24) (reg:P 8)) (clobber (reg:P 8)) and similarly for all the other param regs. Perhaps even make it explicit what exactly is subtracted from %sp. And the second target hook would return a different rtx for DECL_INCOMING_RTL, with registers adjusted back. Because for -O0 if we don't do var-tracking we probably want DECL_INCOMING_RTL to still refer to %i0 etc., even when it is not correct before the save.
