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Date: Sat, 13 Feb 2021 00:20:48 +0100 (CET)
From: Marc Glisse <marc.glisse@inria.fr>
Reply-To: GCC <gcc@gcc.gnu.org>
To: Andrew MacLeod <amacleod@redhat.com>
cc: GCC <gcc@gcc.gnu.org>
Subject: Re: bug in DSE?
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On Fri, 12 Feb 2021, Andrew MacLeod via Gcc wrote:

> I dont't want to immediately open a PR,  so I'll just ask about 
> testsuite/gcc.dg/pr83609.c.
>
> the compilation string  is
>   -O2 -fno-tree-forwprop -fno-tree-ccp -fno-tree-fre -fno-tree-pre 
> -fno-code-hoisting
>
> Which passes as is.
>
> if I however add   -fno-tree-vrp   as well, then it looks like dead store 
> maybe does something wong...
>
> with EVRP running, we translate function foo() from
>
>
> complex float foo ()
> {
>   complex float c;
>   complex float * c.0_1;
>   complex float _4;
>
>   <bb 2> :
>   c.0_1 = &c;
>   MEM[(long long unsigned int *)c.0_1] = 1311768467463790320;
>   _4 = c;

Isn't that a clear violation of strict aliasing?

-- 
Marc Glisse