https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109351
Bug ID: 109351
Summary: RA uses lowest cost for the mode of different
reg_classes w/o considering hard_regno_mode_ok.
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: crazylht at gmail dot com
Target Milestone: ---
575 for (cl = (int) N_REG_CLASSES - 1; cl >= 0; cl--)
576 {
577 if (cl != (int) NO_REGS)
578 for (mode = 0; mode < MAX_MACHINE_MODE; mode++)
579 {
580 ira_max_memory_move_cost[mode][cl][0]
581 = ira_memory_move_cost[mode][cl][0]
582 = memory_move_cost ((machine_mode) mode,
583 (reg_class_t) cl, false);
584 ira_max_memory_move_cost[mode][cl][1]
585 = ira_memory_move_cost[mode][cl][1]
586 = memory_move_cost ((machine_mode) mode,
587 (reg_class_t) cl, true);
588 /* Costs for NO_REGS are used in cost calculation on the
589 1st pass when the preferred register classes are not
590 known yet. In this case we take the best scenario. */
591 if (ira_memory_move_cost[mode][NO_REGS][0]
592 > ira_memory_move_cost[mode][cl][0])
593 ira_max_memory_move_cost[mode][NO_REGS][0]
594 = ira_memory_move_cost[mode][NO_REGS][0]
595 = ira_memory_move_cost[mode][cl][0];
596 if (ira_memory_move_cost[mode][NO_REGS][1]
597 > ira_memory_move_cost[mode][cl][1])
598 ira_max_memory_move_cost[mode][NO_REGS][1]
599 = ira_memory_move_cost[mode][NO_REGS][1]
600 = ira_memory_move_cost[mode][cl][1];
601 }
602 }
It could be a potential performance issue.
It's from PR108707.
