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* [gcc r12-6477] Prevent exponential range calculations.
@ 2022-01-11 14:39 Andrew Macleod
0 siblings, 0 replies; only message in thread
From: Andrew Macleod @ 2022-01-11 14:39 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:71b72132011a47a4b39950d95718f18d1218978c
commit r12-6477-g71b72132011a47a4b39950d95718f18d1218978c
Author: Andrew MacLeod <amacleod@redhat.com>
Date: Mon Jan 10 13:33:44 2022 -0500
Prevent exponential range calculations.
Produce a summary result for any operation involving too many subranges.
PR tree-optimization/103821
* range-op.cc (range_operator::fold_range): Only do precise ranges
when there are not too many subranges.
Diff:
---
gcc/range-op.cc | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/gcc/range-op.cc b/gcc/range-op.cc
index 1af42ebc376..a4f6e9eba29 100644
--- a/gcc/range-op.cc
+++ b/gcc/range-op.cc
@@ -209,10 +209,12 @@ range_operator::fold_range (irange &r, tree type,
unsigned num_rh = rh.num_pairs ();
// If both ranges are single pairs, fold directly into the result range.
- if (num_lh == 1 && num_rh == 1)
+ // If the number of subranges grows too high, produce a summary result as the
+ // loop becomes exponential with little benefit. See PR 103821.
+ if ((num_lh == 1 && num_rh == 1) || num_lh * num_rh > 12)
{
- wi_fold_in_parts (r, type, lh.lower_bound (0), lh.upper_bound (0),
- rh.lower_bound (0), rh.upper_bound (0));
+ wi_fold_in_parts (r, type, lh.lower_bound (), lh.upper_bound (),
+ rh.lower_bound (), rh.upper_bound ());
op1_op2_relation_effect (r, type, lh, rh, rel);
return true;
}
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