2012/9/30 Georg-Johann Lay <a...@gjlay.de>: > Denis Chertykov schrieb: >> >> Georg-Johann Lay: >> >>> PR52543 required to represent a load from non-generic address spaces as >>> UNSPEC >>> instead of as MEM to avoid a gross code bloat. >>> >>> http://gcc.gnu.org/PR52543 >>> >>> lower-subreg's cost model is still broken: It assumes that any loads from >>> MEM >>> are from the generic address space and does not care for address spaces >>> in its >>> cost model. >>> >>> This patch undoes the changes from SVN r185605 >>> >>> http://gcc.gnu.org/viewcvs?view=revision&revision=185605 >>> >>> and installs a different but less intrusive hack around PR52543: >>> >>> targetm.mode_dependent_address_p has an address space parameter so that >>> the >>> backend can pretend all non-generic addresses are mode-dependent. >>> >>> This keeps lower-subreg.c from splitting the loads, and it is possible to >>> represent the loads as MEM and there is no more the need to represent >>> them as >>> UNSPECs. >>> >>> This patch is still not an optimal solution but the code is much closer >>> to a >>> clean solution now. >>> >>> Ok for trunk? >> >> >> You can apply it. >> >> Denis. > > > I also applied the following change: > > http://gcc.gnu.org/viewcvs?view=revision&revision=191825 > > * config/avr/avr.md (adjust_len): Add lpm. > (reload_in<mode>): Use avr_out_lpm for output. Use "lpm" for > adjust_len. > * config/avr/avr-protos.h (avr_out_lpm): New prototype. > * config/avr/avr.c (avr_out_lpm): Make global. > (adjust_insn_length): Handle ADJUST_LEN_LPM. > > The reload_in<mode> insns used the wrong output functions. > > Notice that this change is just a cosmetic change because the secondary > reload for the non-generic spaces are ignored. That is: despite > avr_secondary_reload, REG <- MEM input reloads are not mapped to their > secondary reload insn and the mov insn for that load is used. > > This leads to a situation where the insn output function is not supplied > with the needed clobber register, thus the avr_find_unused_d_reg function is > needed to work around that.
What would happen if no unused_d_reg ? > Denis, do you know why the secondary reloads requested by > avr_secondary_reload are ignored? I see calls to this hook and sri->icode > is set to the right insn code but ignored afterwards. > > The only calls to that hook with the right operands are from ira cost > computation. I have tried to use secondary a few years ago (may be 5 or 7). I have definitely remember only one thing: secondary reload should be avoided as long as possible. The better way to got a knowledge about it is a GDB ;-) > > From the internals I don't see why it is skipped and the responsiveness in > the gcc-help@ list on such topics is zero :-( IMHO it's a question to gcc@ not to gcc-help@ Denis.
