http://gcc.gnu.org/ml/gcc-patches/2012-03/msg00641.html
Georg-Johann Lay wrote: > The problem with the PR is that lower-subreg.c happily splits multi-byte moves > from address spaces without knowing anything about the additional costs this > is > causing. > > The TARGET_MODE_DEPENDENT_ADDRESS_P hook cannot be used for 16-bit addresses > because that hook is not sensitive to address spaces, but is is used for the > 24-bit address space to avoid subreg lowering for PSImode. > > For the 16-bit address spaces the mov expander now assigns the address > register > by hand as post-increment. > > Luckily, post-increment is the only addressing mode that makes sense with the > non-generic address spaces and there is no choice for the address register > resp. addressing mode, anyway... > > This patch does not fix the PR issue, of course, it just avoids subreg > lowering > by using/pretending mode-dependent addresses. > > Ok for trunk? > > Johann > > PR rtl-optimization/52543 > * config/avr/avr.c (avr_mode_dependent_address_p): New function. > (TARGET_MODE_DEPENDENT_ADDRESS_P): New define. > > * config/avr/avr.md (unspec): Add UNSPEC_LPM. > (load_<mode>_libgcc): Use UNSPEC_LPM instead of MEM. > (mov<mode>): For multi-byte move from non-generic > 16-bit address spaces: Expand to use Z++ as address for > inline code and use UNSPEC_LPM (Z) for code from libgcc. > (load<mode>_libgcc): Remove expander. > (split-lpmx): Remove split.
