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More update-ssa speedup

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When working on a smaller region like a loop version copy the main
time spent is now dominance fast query recompute which does a full
function DFS walk.  The dominance queries within the region of
interest should be O(log n) without fast queries and we should do
on the order of O(n) of them which overall means reasonable
complexity.

For the artificial testcase I'm looking at this shaves off
considerable time again.

	* tree-into-ssa.cc (update_ssa): Do not forcefully
	re-compute dominance fast queries for TODO_update_ssa_no_phi.
This commit is contained in:
Richard Biener 2022-07-11 12:17:40 +02:00
parent 415d2c38ed
commit f1782a0a8c
1 changed files with 5 additions and 3 deletions
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8
gcc/tree-into-ssa.cc
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@ -3451,11 +3451,13 @@ update_ssa (unsigned update_flags)
phis_to_rewrite.create (last_basic_block_for_fn (cfun) + 1);
blocks_to_update = BITMAP_ALLOC (NULL);
/* Ensure that the dominance information is up-to-date. */
calculate_dominance_info (CDI_DOMINATORS);
insert_phi_p = (update_flags != TODO_update_ssa_no_phi);
/* Ensure that the dominance information is up-to-date and when we
are going to compute dominance frontiers fast queries are possible. */
if (insert_phi_p || dom_info_state (CDI_DOMINATORS) == DOM_NONE)
calculate_dominance_info (CDI_DOMINATORS);
/* If there are names defined in the replacement table, prepare
definition and use sites for all the names in NEW_SSA_NAMES and
OLD_SSA_NAMES. */