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(create_reg_dead_note): Rewrite so as to conserve registers killed not number of REG_DEAD notes. 

(create_reg_dead_note): Rewrite so as to conserve
registers killed not number of REG_DEAD notes.
(schedule_block): Change comments about dead_notes variable.

From-SVN: r4222
This commit is contained in:
Jim Wilson 1993-04-25 14:24:15 -07:00
parent 51f0e748fa
commit 56b7c17e49
1 changed files with 47 additions and 7 deletions
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54
gcc/sched.c
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@ -2508,12 +2508,19 @@ static void
create_reg_dead_note (reg, insn)
rtx reg, insn;
{
rtx link = dead_notes;
rtx link, backlink;
if (link == 0)
/* In theory, we should not end up with more REG_DEAD reg notes than we
started with. In practice, this can occur as the result of bugs in
flow, combine and/or sched. */
/* The number of registers killed after scheduling must be the same as the
number of registers killed before scheduling. The number of REG_DEAD
notes may not be conserved, i.e. two SImode hard register REG_DEAD notes
might become one DImode hard register REG_DEAD note, but the number of
registers killed will be conserved.
We carefully remove REG_DEAD notes from the dead_notes list, so that
there will be none left at the end. If we run out early, then there
is a bug somewhere in flow, combine and/or sched. */
if (dead_notes == 0)
{
#if 1
abort ();
@ -2523,7 +2530,40 @@ create_reg_dead_note (reg, insn)
#endif
}
else
dead_notes = XEXP (dead_notes, 1);
{
/* Number of regs killed by REG. */
int regs_killed = (REGNO (reg) >= FIRST_PSEUDO_REGISTER ? 1
: HARD_REGNO_NREGS (REGNO (reg), GET_MODE (reg)));
/* Number of regs killed by REG_DEAD notes taken off the list. */
int reg_note_regs;
link = dead_notes;
reg_note_regs = (REGNO (XEXP (link, 0)) >= FIRST_PSEUDO_REGISTER ? 1
: HARD_REGNO_NREGS (REGNO (XEXP (link, 0)),
GET_MODE (XEXP (link, 0))));
while (reg_note_regs < regs_killed)
{
link = XEXP (link, 1);
reg_note_regs += (REGNO (XEXP (link, 0)) >= FIRST_PSEUDO_REGISTER ? 1
: HARD_REGNO_NREGS (REGNO (XEXP (link, 0)),
GET_MODE (XEXP (link, 0))));
}
dead_notes = XEXP (link, 1);
/* If we took too many regs kills off, put the extra ones back. */
while (reg_note_regs > regs_killed)
{
rtx temp_reg, temp_link;
temp_reg = gen_rtx (REG, word_mode, 0);
temp_link = rtx_alloc (EXPR_LIST);
PUT_REG_NOTE_KIND (temp_link, REG_DEAD);
XEXP (temp_link, 0) = temp_reg;
XEXP (temp_link, 1) = dead_notes;
dead_notes = temp_link;
reg_note_regs--;
}
}
XEXP (link, 0) = reg;
XEXP (link, 1) = REG_NOTES (insn);
@ -3654,7 +3694,7 @@ schedule_block (b, file)
head = note_head;
}
/* In theory, there should be no REG_DEAD notes leftover at the end.
/* There should be no REG_DEAD notes leftover at the end.
In practice, this can occur as the result of bugs in flow, combine.c,
and/or sched.c. The values of the REG_DEAD notes remaining are
meaningless, because dead_notes is just used as a free list. */