--- Comment #19 from CVS Commits <cvs-commit at gcc dot> ---
The master branch has been updated by Jeff Law <>:

commit r10-7380-g713ecb3d417363a4b12c725b335fce10355da206
Author: Jeff Law <>
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  <>

                PR target/94254
                * config/rs6000/rs6000.c (rs6000_can_change_mode_class): Allow
                FPRs to change between SDmode and DDmode.

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