Hi,
This change deals with reloading a subreg(reg) using the inner mode
to prevent partial spilling of data like in the case described here:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78660#c8
No test case for now but I am investigating a targeted test using
the RTL frontend for later submission.
Thanks,
Matthew
gcc/
PR target/78660
* lra-constraints.c (curr_insn_transform): Handle
WORD_REGISTER_OPERATIONS requirements when reloading SUBREGs.
---
gcc/lra-constraints.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/gcc/lra-constraints.c b/gcc/lra-constraints.c
index 22323b2..f29308f 100644
--- a/gcc/lra-constraints.c
+++ b/gcc/lra-constraints.c
@@ -4130,7 +4130,14 @@ curr_insn_transform (bool check_only_p)
&& (goal_alt[i] == NO_REGS
|| (simplify_subreg_regno
(ira_class_hard_regs[goal_alt[i]][0],
- GET_MODE (reg), byte, mode) >= 0)))))
+ GET_MODE (reg), byte, mode) >= 0)))
+ /* WORD_REGISTER_OPERATIONS targets require the register
+ to be reloaded when the outer mode is strictly
+ narrower than the inner mode. Note: It may be
+ necessary to always reload the inner mode here but it
+ requires further investigation. */
+ || (GET_MODE_SIZE (mode) < GET_MODE_SIZE (GET_MODE (reg))
+ && WORD_REGISTER_OPERATIONS)))
{
if (type == OP_OUT)
type = OP_INOUT;
--
2.2.1
