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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/107565] -Wanalyzer-use-of-uninitialized-value false
 positive with rdrand
Date: Tue, 08 Nov 2022 05:39:48 +0000
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X-Bugzilla-Keywords: missed-optimization
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107565

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |missed-optimization
             Status|UNCONFIRMED                 |NEW
             Target|                            |x86_64
   Last reconfirmed|                            |2022-11-08
          Component|analyzer                    |target
           Assignee|dmalcolm at gcc dot gnu.org        |unassigned at gcc d=
ot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.
      else if (!fndecl_has_gimple_body_p (callee_fndecl)
               && (!(callee_fndecl_flags & (ECF_CONST | ECF_PURE)))
               && !fndecl_built_in_p (callee_fndecl))
        unknown_side_effects =3D true;

The last part is part of the problem I think. At least here.
Yes maybe we should have another builtin which returns a "_Complex unsigned
long long" here which is folded into for __builtin_ia32_rdrand*_step to rem=
ove
the need to the address too.

I am going to declare this one as a target issue but there might be other
builtins which are harder to do the "_Complex" trick.=