https://gcc.gnu.org/g:d1a7529aaec43878cc0d0a5e754d894a1857d18a
commit d1a7529aaec43878cc0d0a5e754d894a1857d18a
Author: Michael Meissner <meiss...@linux.ibm.com>
Date: Thu Apr 25 18:10:35 2024 -0400
Make moves from SPRs higher in cost.
2024-04-25 Michael Meissner <meiss...@linux.ibm.com>
gcc/
* config/rs6000/rs6000.cc (rs6000_register_move_cost): Make moves
from
SPRs more expensive.
Diff:
---
gcc/config/rs6000/rs6000.cc | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
index 908ad5dcb58..d498f62be7a 100644
--- a/gcc/config/rs6000/rs6000.cc
+++ b/gcc/config/rs6000/rs6000.cc
@@ -22813,6 +22813,16 @@ rs6000_register_move_cost (machine_mode mode,
ret = 2 * hard_regno_nregs (reg, mode);
}
+ /* Make moves from SPR registers (LR, CTR, TAR) more expensive so that the
+ register allocator does not think of these registers are useful for saving
+ results. */
+ else if (reg_classes_intersect_p (from, SPECIAL_REGS)
+ && reg_classes_intersect_p (to, GENERAL_REGS))
+ {
+ rclass = from;
+ ret = 6;
+ }
+
/* Moves from/to GENERAL_REGS. */
else if ((rclass = from, reg_classes_intersect_p (to, GENERAL_REGS))
|| (rclass = to, reg_classes_intersect_p (from, GENERAL_REGS)))
