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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/114480] [12/13/14 Regression] g++: internal compiler error:
 Segmentation fault signal terminated program cc1plus
Date: Tue, 09 Apr 2024 11:39:50 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D114480

--- Comment #30 from Richard Biener <rguenth at gcc dot gnu.org> ---
Temporarily memory goes to out-of-SSA computing liveness (2GB), after RTL
expansion it drops to ~900MB peak again.  Then df-init-at-O0 bumps to 1.3GB=
 and
then IRA goes all the way to >3GB.  We're using lra_simple_p because
num_used_regs is 343033 and last_basic_block is 117142.  It's df_analyze ()
which brings memory usage to 2.8GB.  After ira_build () it's 3.4GB.

There's 1.5GB used in LR problem data bitmaps, we are not separating the
local computed bitmaps from the global solution (the DF machinery doesn't
have a separate "local compute" free, possibly the finalize hook can be
used for this).  Though the local compute bitmaps only use around 20MB.
The DF bitmap obstack itself is quite small as well.

Of course it's all because we fail to implement the initializers EH
cleanup in a more sensible way.  Complete "elements" could be processed
in a loop over the containers elements while only a single partially
under-construction element would need to be handled "inline".=