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| author | Jeff Law <law@redhat.com> | 2020-03-25 10:37:31 -0600 |
|---|---|---|
| committer | Jeff Law <law@redhat.com> | 2020-03-25 10:37:31 -0600 |
| commit | 713ecb3d417363a4b12c725b335fce10355da206 (patch) | |
| tree | 1e9b1629c0cd19232bdaca4a799e78fd76d0cfeb | |
| parent | c7a252ba2d0a08397d8fc6d6dc7db34f90f76acb (diff) | |
| download | gcc-713ecb3d417363a4b12c725b335fce10355da206.zip gcc-713ecb3d417363a4b12c725b335fce10355da206.tar.gz gcc-713ecb3d417363a4b12c725b335fce10355da206.tar.bz2 | |
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.sandiford@arm.com>
gcc/
PR target/94254
* config/rs6000/rs6000.c (rs6000_can_change_mode_class): Allow
FPRs to change between SDmode and DDmode.
| -rw-r--r-- | gcc/ChangeLog | 6 | ||||
| -rw-r--r-- | gcc/config/rs6000/rs6000.c | 9 |
2 files changed, 15 insertions, 0 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index b75ac74..7678776 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,9 @@ +2020-03-25 Richard Sandiford <richard.sandiford@arm.com> + + PR target/94254 + * config/rs6000/rs6000.c (rs6000_can_change_mode_class): Allow + FPRs to change between SDmode and DDmode. + 2020-03-25 Martin Sebor <msebor@redhat.com> PR tree-optimization/94131 diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c index 7505a0e..5b36593 100644 --- a/gcc/config/rs6000/rs6000.c +++ b/gcc/config/rs6000/rs6000.c @@ -12307,6 +12307,15 @@ rs6000_can_change_mode_class (machine_mode from, if (!BYTES_BIG_ENDIAN && (to == TDmode || from == TDmode)) return false; + /* Allow SD<->DD changes, since SDmode values are stored in + the low half of the DDmode, just like target-independent + code expects. We need to allow at least SD->DD since + rs6000_secondary_memory_needed_mode asks for that change + to be made for SD reloads. */ + if ((to == DDmode && from == SDmode) + || (to == SDmode && from == DDmode)) + return true; + if (from_size < 8 || to_size < 8) return false; |