Hi,
We have this charming move_insn function in haifa-sched.c:
/* Move INSN. Reemit notes if needed.
Return the last insn emitted by the scheduler, which is the
return value from the first call to reemit_notes. */
static rtx
move_insn (rtx insn, rtx last)
{
rtx retval = NULL;
move_insn1 (insn, last);
/* If this is the first call to reemit_notes, then record
its return value. */
if (retval == NULL_RTX)
retval = reemit_notes (insn, insn);
else
reemit_notes (insn, insn);
SCHED_GROUP_P (insn) = 0;
return retval;
}
First of all, move_insn1 should really be replaced with reorder_insns,
but OK, whatever, this code is older.
But what is this weird thing move_insn is doing with retval? It is
pretty obvious that retval is NULL_RTX in "if (retval == NULL_RTX)",
so I wonder what the purpose was of this code. Archeology hasn't
helped me much. retval was introduced in revision 1.8 by Jeff:
1.1 law 6501:
6502: static rtx
6503: move_insn (insn, last)
6504: rtx insn, last;
6505: {
1.8 |law 6506: rtx retval = NULL;
1.1 law 6507:
1.8 |law 6508: /* If INSN has SCHED_GROUP_P set, then issue it
and any other
| 6509: insns with SCHED_GROUP_P set first. */
1.1 law 6510: while (SCHED_GROUP_P (insn))
6511: {
6512: rtx prev = PREV_INSN (insn);
1.8 |law 6513:
| 6514: /* Move a SCHED_GROUP_P insn. */
1.1 law 6515: move_insn1 (insn, last);
1.8 |law 6516: /* If this is the first call to
reemit_notes, then record
| 6517: its return value. */
| 6518: if (retval == NULL_RTX)
| 6519: retval = reemit_notes (insn, insn);
| 6520: else
| 6521: reemit_notes (insn, insn);
1.1 law 6522: insn = prev;
6523: }
6524:
1.8 |law 6525: /* Now move the first non SCHED_GROUP_P insn.
*/
1.1 law 6526: move_insn1 (insn, last);
1.8 |law 6527:
| 6528: /* If this is the first call to reemit_notes,
then record
| 6529: its return value. */
| 6530: if (retval == NULL_RTX)
| 6531: retval = reemit_notes (insn, insn);
| 6532: else
| 6533: reemit_notes (insn, insn);
| 6534:
| 6535: return retval;
1.1 law 6536: }
But in revision 1.215, the itanium-sched-branch was merged and the
function was simplified to:
law 1765:
1766: static rtx
1767: move_insn (insn, last)
1768: rtx insn, last;
1769: {
1.8 law 1770: rtx retval = NULL;
1.1 law 1771:
1.8 law 1772: /* Now move the first non SCHED_GROUP_P insn.
*/
1.1 law 1773: move_insn1 (insn, last);
1.8 law 1774:
1775: /* If this is the first call to reemit_notes,
then record
1776: its return value. */
1777: if (retval == NULL_RTX)
1778: retval = reemit_notes (insn, insn);
1779: else
1780: reemit_notes (insn, insn);
1781:
1.215 |vmakarov 1782: SCHED_GROUP_P (insn) = 0;
| 1783:
1.8 law 1784: return retval;
1.1 law 1785: }
The only ChangeLog entry I can find for this change is:
* sched-rgn.c (init_ready_list, can_schedule_ready_p,
add_branch_dependences): Ignore schedule groups.
* sched-ebb.c (init_ready_list): Ditto.
* (move_insn, set_priorities): Ditto.
Vlad, can you explain this change? Can I safely clean up this function,
or should we still avoid calling reemit_notes more than once for each
insn???
Gr.
Steven
