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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/102622] [9/10 Regression] Wrong code with -O1
 and above due to phiopt and signed one bit integer types
Date: Sun, 10 Oct 2021 09:18:51 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102622

--- Comment #22 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Here is the simple patch which I will test for both GCC 10 and GCC 9.

The question becomes does it make sense to make the same change to GCC 11 e=
ven
if it cannot be hit.

diff --git a/gcc/tree-ssa-phiopt.c b/gcc/tree-ssa-phiopt.c
index 9ed26a3d45f..a6c197defea 100644
--- a/gcc/tree-ssa-phiopt.c
+++ b/gcc/tree-ssa-phiopt.c
@@ -770,9 +770,12 @@ conditional_replacement (basic_block cond_bb, basic_bl=
ock
middle_bb,
   if ((integer_zerop (arg0) && integer_onep (arg1))
       || (integer_zerop (arg1) && integer_onep (arg0)))
     neg =3D false;
+  /* For signed one bit types, the negation is not needed and
+     should be avoided and is the same as 1 case for non-signed
+     one bit types.  */
   else if ((integer_zerop (arg0) && integer_all_onesp (arg1))
           || (integer_zerop (arg1) && integer_all_onesp (arg0)))
-    neg =3D true;
+    neg =3D TYPE_PRECISION (TREE_TYPE (arg0)) !=3D 1;
   else
     return false;=