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From: "rsandifo at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/98863] [11 Regression] WRF with LTO consumes a
 lot of memory in REE, FWPROP and x86 specific passes
Date: Mon, 08 Feb 2021 08:45:47 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98863

--- Comment #39 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.o=
rg> ---
Just to give an update on this: I have a patch that reduces the
amount of memory consumed by fwprop so that it no longer seems
to be outlier.  However, it involves doing more bitmap operations.
In this testcase we have a larger number of registers that
seem to be live but unused across a large region of code,
so bitmap ANDs with the live in sets are expensive and hit
the worst-case O(nblocks=C3=97nregisters).  I'm still trying to find
a way of reducing the effect of that.=