https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94254
--- Comment #19 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jeff Law <l...@gcc.gnu.org>: https://gcc.gnu.org/g:713ecb3d417363a4b12c725b335fce10355da206 commit r10-7380-g713ecb3d417363a4b12c725b335fce10355da206 Author: Jeff Law <l...@redhat.com> Date: Wed Mar 25 10:37:31 2020 -0600 rs6000: Allow FPRs to change between SDmode and DDmode [PR94254] g:497498c878d48754318e486428e2aa30854020b9 caused lra to cycle on some SDmode reloads for power6. As explained in more detail in the PR comments, the problem was a conflict between two target hooks: rs6000_secondary_memory_needed_mode required SDmode FPR reloads to use DDmode memory (rightly, since using SDmode memory wouldn't make progress) but rs6000_can_change_mode_class didn't allow FPRs to change from SDmode to DDmode. Previously lra ignored that and changed the mode anyway. From what Segher says, it sounds like the "from_size < 8 || to_size < 8" check is mostly there for SF<->64-bit subregs, and that SDmode is stored in the way that target-independent code expects. This patch therefore allows SD<->DD changes. I wondered about checking for SD<->64-bit changes instead, but that seemed like an unnecessary generalisation for this stage. 2020-03-23 Richard Sandiford <richard.sandif...@arm.com> gcc/ PR target/94254 * config/rs6000/rs6000.c (rs6000_can_change_mode_class): Allow FPRs to change between SDmode and DDmode.
