https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108707
Hongtao.liu <crazylht at gmail dot com> changed:
What |Removed |Added
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Target| |x86_64-*-* i?86-*-*
--- Comment #1 from Hongtao.liu <crazylht at gmail dot com> ---
It's related to memory_move_cost, in RA
1466 /* If this insn loads a parameter from its stack slot, then it
1467 represents a savings, rather than a cost, if the parameter is
1468 stored in memory. Record this fact.
1469
1470 Similarly if we're loading other constants from memory (constant
1471 pool, TOC references, small data areas, etc) and this is the only
1472 assignment to the destination pseudo.
1473
1474 Don't do this if SET_SRC (set) isn't a general operand, if it is
1475 a memory requiring special instructions to load it, decreasing
1476 mem_cost might result in it being loaded using the specialized
1477 instruction into a register, then stored into stack and loaded
1478 again from the stack. See PR52208.
1479
1480 Don't do this if SET_SRC (set) has side effect. See PR56124. */
1481 if (set != 0 && REG_P (SET_DEST (set)) && MEM_P (SET_SRC (set))
1482 && (note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) != NULL_RTX
1483 && ((MEM_P (XEXP (note, 0))
1484 && !side_effects_p (SET_SRC (set)))
1485 || (CONSTANT_P (XEXP (note, 0))
1486 && targetm.legitimate_constant_p (GET_MODE (SET_DEST (set)),
1487 XEXP (note, 0))
1488 && REG_N_SETS (REGNO (SET_DEST (set))) == 1))
1489 && general_operand (SET_SRC (set), GET_MODE (SET_SRC (set)))
1490 /* LRA does not use equiv with a symbol for PIC code. */
1491 && (! ira_use_lra_p || ! pic_offset_table_rtx
1492 || ! contains_symbol_ref_p (XEXP (note, 0))))
1493 {
1494 enum reg_class cl = GENERAL_REGS;
1495 rtx reg = SET_DEST (set);
1496 int num = COST_INDEX (REGNO (reg));
1497
1498 COSTS (costs, num)->mem_cost
1499 -= ira_memory_move_cost[GET_MODE (reg)][cl][1] * frequency;
1500 record_address_regs (GET_MODE (SET_SRC (set)),
1501 MEM_ADDR_SPACE (SET_SRC (set)),
1502 XEXP (SET_SRC (set), 0), 0, MEM, SCRATCH,
1503 frequency * 2);
1504 counted_mem = true;
we use GENERAL_REGS for E_V16SFmode move cost which should be inaccurate, i
think when preferred regclass is unknown, we'd better use NO_REGS.
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. */
