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From: "aldyh at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/95649] [11 Regression] ICE during GIMPLE
 pass: cunroll since r11-1146-g1396fa5b91cfa0b3
Date: Tue, 16 Jun 2020 18:59:38 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95649

Aldy Hernandez <aldyh at gcc dot gnu.org> changed:

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

--- Comment #10 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
(In reply to Jeffrey A. Law from comment #8)
> I still don't understand why propagating one SSA_NAME for another is caus=
ing
> headaches later though.=20

TBH, I don't either.

When I compile the .c test in this PR with the following options:

-O2 -fno-tree-scev-cprop -fdisable-tree-ccp1  -fdisable-tree-ccp2
-fdisable-tree-copyprop1 -fdisable-tree-evrp -fdisable-tree-vrp1
-fdisable-tree-ccp1 -fdisable-tree-ccp2 -fdisable-tree-ccp3

...I still get an ICE, but there is no change in the IL between trunk witho=
ut
the offending patch, and with the patch that broke the test.  This would
indicate that there is some on-the-side structure that is being altered by =
the
phi argument propagation.

I did notice that the IL *does* change in the middle of one of the copyprop=
 (or
ccp?) passes, but it gets cleaned up to whatever was there before.

Later in SCEV, we ICE while trying to look at the SSA_NAME_DEF_STMT of an S=
SA
which no longer exists in the IL.  This happens in
chrec_contains_symbols_defined_in_loop().  A wild guess is that the loop in=
fo
is getting mucked up somehow.

I can investigate more deeply if desired, but since this was a silly typo, =
I'm
gonna leave it alone for now.

Closing as fixed in mainline.=