r14-172-g0368d169492017 replaces GENERAL_REGS with NO_REGS in cost
calculation when the preferred register class are not known yet.
It regressed powerpc PR109610 and PR109858, it looks too aggressive to use
NO_REGS when mode can be allocated with GENERAL_REGS.
The patch takes a step back, still use GENERAL_REGS when
hard_regno_mode_ok for mode and GENERAL_REGS, otherwise uses NO_REGS.
Kewen confirmed the patch fixed PR109858, I vefiried it also fixed PR109610.
Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}.
No big performance impact for SPEC2017 on icelake server.
Ok for trunk?
gcc/ChangeLog:
* ira-costs.cc (scan_one_insn): Only use NO_REGS in cost
calculation when !hard_regno_mode_ok for GENERAL_REGS and
mode, otherwise still use GENERAL_REGS.
---
gcc/ira-costs.cc | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/gcc/ira-costs.cc b/gcc/ira-costs.cc
index d2a801ab9b0..ae8304ff938 100644
--- a/gcc/ira-costs.cc
+++ b/gcc/ira-costs.cc
@@ -1572,12 +1572,16 @@ scan_one_insn (rtx_insn *insn)
&& (! ira_use_lra_p || ! pic_offset_table_rtx
|| ! contains_symbol_ref_p (XEXP (note, 0))))
{
- /* Costs for NO_REGS are used in cost calculation on the
- 1st pass when the preferred register classes are not
- known yet. In this case we take the best scenario. */
- enum reg_class cl = NO_REGS;
+ enum reg_class cl = GENERAL_REGS;
rtx reg = SET_DEST (set);
int num = COST_INDEX (REGNO (reg));
+ /* Costs for NO_REGS are used in cost calculation on the
+ 1st pass when the preferred register classes are not
+ known yet. In this case we take the best scenario when
+ mode can't be put into GENERAL_REGS. */
+ if (!targetm.hard_regno_mode_ok (ira_class_hard_regs[cl][0],
+ GET_MODE (reg)))
+ cl = NO_REGS;
COSTS (costs, num)->mem_cost
-= ira_memory_move_cost[GET_MODE (reg)][cl][1] * frequency;
--
2.39.1.388.g2fc9e9ca3c
