http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52208
--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-02-14
13:58:44 UTC ---
The -1000 costs comes from the scan_one_insn subtracting there
ira_memory_move_cost[][][] * frequency (i.e. memory_cost becomes -4000) and
on the plus we add just 3000 to memory_cost.
I wonder if we shouldn't limit this subtraction of mem_cost / setting of
counted_mem e.g. to general_operand (SET_SRC (set), GET_MODE (SET_SRC (set)))
and leave the specialized memory loads alone (I know, it would be a hack, but
works for this and shouldn't pessimize the cases for which this hunk has been
added). And would at least tiny bit model what reload will do with such
non-standard mems - as on this testcase it doesn't use the orignal mem, but
does the load, followed by store to another mem, followed by load from that
mem.
--- ira-costs.c.jj 2012-01-20 12:35:17.000000000 +0100
+++ ira-costs.c 2012-02-14 14:54:52.297356053 +0100
@@ -1313,7 +1313,8 @@ scan_one_insn (rtx insn)
|| (CONSTANT_P (XEXP (note, 0))
&& targetm.legitimate_constant_p (GET_MODE (SET_DEST (set)),
XEXP (note, 0))
- && REG_N_SETS (REGNO (SET_DEST (set))) == 1)))
+ && REG_N_SETS (REGNO (SET_DEST (set))) == 1))
+ && general_operand (SET_SRC (set), GET_MODE (SET_SRC (set))))
{
enum reg_class cl = GENERAL_REGS;
rtx reg = SET_DEST (set);
