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re PR tree-optimization/19038 (tree-ssa causing loops to have more than one BB)

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PR tree-optimization/19038
	* tree-ssa-loop-ivopts.c (allow_ip_end_pos_p): New function.
	(add_candidate): Add ivs with increment in latch only if
	allow_ip_end_pos_p is true.
	(determine_iv_cost): Use empty_block_p.

From-SVN: r93925
This commit is contained in:
Zdenek Dvorak 2005-01-19 23:50:04 +01:00 committed by Zdenek Dvorak
parent 75aa3f658c
commit 4366cf6d6f
2 changed files with 35 additions and 12 deletions
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8
gcc/ChangeLog
View File

@ -1,3 +1,11 @@
2005-01-19 Zdenek Dvorak <dvorakz@suse.cz>
PR tree-optimization/19038
* tree-ssa-loop-ivopts.c (allow_ip_end_pos_p): New function.
(add_candidate): Add ivs with increment in latch only if
allow_ip_end_pos_p is true.
(determine_iv_cost): Use empty_block_p.
2005-01-19 Daniel Berlin <dberlin@dberlin.org>
* cfganal.c (compute_dominance_frontiers_1): Replace with new algorithm

39
gcc/tree-ssa-loop-ivopts.c
View File

@ -1779,6 +1779,27 @@ add_candidate_1 (struct ivopts_data *data,
return cand;
}
/* Returns true if incrementing the induction variable at the end of the LOOP
is allowed.
The purpose is to avoid splitting latch edge with a biv increment, thus
creating a jump, possibly confusing other optimization passes and leaving
less freedom to scheduler. So we allow IP_END_POS only if IP_NORMAL_POS
is not available (so we do not have a better alternative), or if the latch
edge is already nonempty. */
static bool
allow_ip_end_pos_p (struct loop *loop)
{
if (!ip_normal_pos (loop))
return true;
if (!empty_block_p (ip_end_pos (loop)))
return true;
return false;
}
/* Adds a candidate BASE + STEP * i. Important field is set to IMPORTANT and
position to POS. If USE is not NULL, the candidate is set as related to
it. The candidate computation is scheduled on all available positions. */
@ -1789,7 +1810,8 @@ add_candidate (struct ivopts_data *data,
{
if (ip_normal_pos (data->current_loop))
add_candidate_1 (data, base, step, important, IP_NORMAL, use, NULL_TREE);
if (ip_end_pos (data->current_loop))
if (ip_end_pos (data->current_loop)
&& allow_ip_end_pos_p (data->current_loop))
add_candidate_1 (data, base, step, important, IP_END, use, NULL_TREE);
}
@ -3518,8 +3540,7 @@ static void
determine_iv_cost (struct ivopts_data *data, struct iv_cand *cand)
{
unsigned cost_base, cost_step;
tree base, last;
basic_block bb;
tree base;
if (!cand->iv)
{
@ -3543,15 +3564,9 @@ determine_iv_cost (struct ivopts_data *data, struct iv_cand *cand)
/* Prefer not to insert statements into latch unless there are some
already (so that we do not create unnecessary jumps). */
if (cand->pos == IP_END)
{
bb = ip_end_pos (data->current_loop);
last = last_stmt (bb);
if (!last
|| TREE_CODE (last) == LABEL_EXPR)
cand->cost++;
}
if (cand->pos == IP_END
&& empty_block_p (ip_end_pos (data->current_loop)))
cand->cost++;
}
/* Determines costs of computation of the candidates. */