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From: "rafal at bursig dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/99693] -O2 not move 'if' checks on const data outside the loops
Date: Mon, 22 Mar 2021 09:23:37 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99693

--- Comment #4 from rafal at bursig dot org ---
but using  -O2 -funswitch-loops will bring me those problems why this flag =
is
not in default -O2. Which is not a solution.

Maybe -O2 may have weaken version of this optimization and will work only if
one of if brock is empty. And -O3 will have full version.=20

Example:

form:
for(...)
{
 if (local_value)
 {
   logic;
 }
}
To:
if (local_value)
for(...)
{
   logic;
}

I know that such code could be fixed by developer but gcc don't generate any
diagnostic message about such constructions and for a large project it's
difficult to find all of such places=