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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/94166] [10 Regression] random -fcompare-debug
 failures since r10-1913
Date: Mon, 16 Mar 2020 08:07:35 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D94166

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Oops, I've screwed up, the commit log should have been:
reassoc: Avoid code generation to depend on hash_map traversal [PR94166]

On the following testcase, if there is ASLR, the compiler generates=20=20=
=20=20=20=20=20=20=20=20=20=20=20
different code each time (out of 1000 invocations 994 unique assembler=20=
=20=20=20=20=20=20=20=20=20
contents).  The problem is that undistribute_bitref_for_vector uses=20=20=
=20=20=20=20=20=20=20=20=20=20=20
a hash_map from a tree (SSA_NAME) to a vector and such a hash_map is=20=20=
=20=20=20=20=20=20=20=20=20=20
by default doing pointer hashing on the SSA_NAME rather than using=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20
something stable (SSA_NAME_VERSION).=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20
One possible way would be to use SSA_NAME_VERSION as hash function,=20=20=
=20=20=20=20=20=20=20=20=20=20=20
but given that we from the hash_map traversal just populate a vector=20=20=
=20=20=20=20=20=20=20=20=20=20
which is then sorted, I think it is easier to make the sort callback=20=20=
=20=20=20=20=20=20=20=20=20=20
use SSA_NAME_VERSION as secondary sorting key and thus ensure stable=20=20=
=20=20=20=20=20=20=20=20=20=20
sort (that is generally desirable anyway).=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20

instead.  Sorry.=