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rtl-optimization/104686 - speed up conflict iteration

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The following replaces

       /* Skip bits that are zero.  */
       for (; (word & 1) == 0; word >>= 1)
         bit_num++;

idioms in ira-int.h in the attempt to speedup update_conflict_hard_regno_costs
which we're bound on in PR104686.  The trick is to use ctz_hwi here
which should pay off even with dense bitmaps on architectures that
have HW support for this.

For the PR in question this speeds up compile-time from 31s to 24s for
me.

2022-02-25  Richard Biener  <rguenther@suse.de>

	PR rtl-optimization/104686
	* ira-int.h (minmax_set_iter_cond): Use ctz_hwi to elide loop
	skipping bits that are zero.
	(ira_object_conflict_iter_cond): Likewise.
This commit is contained in:
Richard Biener 2022-02-25 14:19:44 +01:00
parent 50d9ca7104
commit a8250bbaeb
1 changed files with 6 additions and 4 deletions
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10
gcc/ira-int.h
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@ -764,8 +764,9 @@ minmax_set_iter_cond (minmax_set_iterator *i, int *n)
}
/* Skip bits that are zero. */
for (; (i->word & 1) == 0; i->word >>= 1)
i->bit_num++;
int off = ctz_hwi (i->word);
i->bit_num += off;
i->word >>= off;
*n = (int) i->bit_num + i->start_val;
@ -1379,8 +1380,9 @@ ira_object_conflict_iter_cond (ira_object_conflict_iterator *i,
}
/* Skip bits that are zero. */
for (; (word & 1) == 0; word >>= 1)
bit_num++;
int off = ctz_hwi (word);
bit_num += off;
word >>= off;
obj = ira_object_id_map[bit_num + i->base_conflict_id];
i->bit_num = bit_num + 1;