--- 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>:
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 <
check is mostly there for SF<->64-bit subregs, and that SDmode is
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>
* config/rs6000/rs6000.c (rs6000_can_change_mode_class): Allow
FPRs to change between SDmode and DDmode.