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haifa-sched.c (rank_for_schedule): For "equally good insns", prefer the insn which has the most insns dependent on it. 

* haifa-sched.c (rank_for_schedule): For "equally good insns", prefer
        the insn which has the most insns dependent on it.

From-SVN: r20243
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Jeffrey A Law 1998-06-05 11:32:28 +00:00 committed by Jeff Law
parent 192231fbe5
commit 2db4599393
2 changed files with 23 additions and 2 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
Fri Jun 5 12:29:28 1998 Jeffrey A Law (law@cygnus.com)
* haifa-sched.c (rank_for_schedule): For "equally good insns", prefer
the insn which has the most insns dependent on it.
Fri Jun 5 09:03:22 1998 John Carr <jfc@mit.edu>
* alias.c (find_base_value): Avoid reading past end of reg_base_value.

20
gcc/haifa-sched.c
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@ -87,7 +87,8 @@
broken by
6. choose insn with the least dependences upon the previously
scheduled insn, or finally
7. choose insn with lowest UID.
7 choose the insn which has the most insns dependent on it.
8. choose insn with lowest UID.
Memory references complicate matters. Only if we can be certain
that memory references are not part of the data dependency graph
@ -4029,7 +4030,7 @@ rank_for_schedule (x, y)
rtx tmp = *(rtx *)y;
rtx tmp2 = *(rtx *)x;
rtx link;
int tmp_class, tmp2_class;
int tmp_class, tmp2_class, depend_count1, depend_count2;
int val, priority_val, spec_val, prob_val, weight_val;
@ -4090,6 +4091,21 @@ rank_for_schedule (x, y)
return val;
}
/* Prefer the insn which has more later insns that depend on it.
This gives the scheduler more freedom when scheduling later
instructions at the expense of added register pressure. */
depend_count1 = 0;
for (link = INSN_DEPEND (tmp); link; link = XEXP (link, 1))
depend_count1++;
depend_count2 = 0;
for (link = INSN_DEPEND (tmp2); link; link = XEXP (link, 1))
depend_count2++;
val = depend_count2 - depend_count1;
if (val)
return val;
/* If insns are equally good, sort by INSN_LUID (original insn order),
so that we make the sort stable. This minimizes instruction movement,
thus minimizing sched's effect on debugging and cross-jumping. */