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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/97623] [9/10/11 Regression] Extremely slow O2
 compile (>>O(n^2))
Date: Fri, 30 Oct 2020 13:28:12 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D97623

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
So this is the change improving the hoist insert situation but it is not a
solution for the back-to-back of PRE vs. hoist insertion.  Will have to thi=
nk
about this some more and then eventually simply add some iteration limit - =
we
can stop after any arbitrary number of iterations after all, the cost is ju=
st
less optimization.

As a workaround for older code bases I suggest to use -fno-code-hoisting for
now.

If you are set up to try current trunk GCC then I'd be curious to know the
effect of the patch on the "real" case.=