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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/102814] [12 regression]
 quadratique/exponential time complexity for max-jump-thread-duplication-stmts
Date: Tue, 19 Oct 2021 07:40:19 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102814

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Aldy Hernandez from comment #1)
> Question to the larger audience... do we support bug reports against
> internal --param constructs?

Yes.  Generally 'max-jump-thread-duplication-stmts' would suggest this is
a parameter limiting code size growth and one that might affect compile-time
in a linear fashion - exponential growth here is unexpected.  The reporter
states a 180 -> 181 parameter change trips this over unexpectedly which is
a case worth investigating (it suggests a limit elsewhere is missing).

For example the alias walking code counts the amount of "work" it does and
has a limit on that, allowing linear growth parametrization.  Not sure if
there's sth in the threader and/or ranger that would support accumulating
a work budget and stop after it is exhausted, but something like that would
be very useful (not sure if that's the problem at hand in this case).=