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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/108552] Linux i386 kernel 5.14 memory
 corruption for pre_compound_page() when gcov is enabled
Date: Mon, 30 Jan 2023 08:30:52 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108552

--- Comment #44 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
I guess we should try and see.
For volatile,
--- gcc/coverage.cc     2023-01-02 09:32:37.078072992 +0100
+++ gcc/coverage.cc     2023-01-30 09:24:45.219951352 +0100
@@ -774,6 +774,7 @@ build_var (tree fn_decl, tree type, int
   TREE_STATIC (var) =3D 1;
   TREE_ADDRESSABLE (var) =3D 1;
   DECL_NONALIASED (var) =3D 1;
+  TREE_THIS_VOLATILE (var) =3D 1;
   SET_DECL_ALIGN (var, TYPE_ALIGN (type));

   return var;

would do it I think (but it should be conditional on new -fupdate-profile
modes, single-volatile and prefer-atomic-volatile or something similar).
Or perhaps insert asm volatile ("" : "+g" (tmp)); in between the load and s=
tore
and see how that compares to the volatile vars? Or adding another flag on t=
he
gcov vars next to DECL_NONALIASED and just avoid specific optimizations on =
it
that somebody runs into (not as reliable but could be faster) - for now
hoisting in LIM and sinking.=