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From: "williambader at hotmail dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug rtl-optimization/89965] [8 Regression] wrong code with -O -mtune=nano-x2 -fcaller-saves -fexpensive-optimizations -fno-tree-dce -fno-tree-ter Date: Fri, 12 Mar 2021 04:11:30 +0000 [thread overview] Message-ID: <bug-89965-4-8uHS5V3oV0@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-89965-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89965 William Bader <williambader at hotmail dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |williambader at hotmail dot com --- Comment #17 from William Bader <williambader at hotmail dot com> --- Something similar to this might be back in gcc 10. I have gcc-10.2.1-9.fc32.x86_64 (gcc 10.2.1 from Fedora 32) and it also happens on gcc-10.2.0 built from source on CentOS 6.10. I have a 64 bit CPU, but I am building a 32 bit executable. I have a 30K line C module that misbehaves with "-O1 -fcaller-saves -fexpensive-optimizations". It works with less optimization (-O1, -O0, or either of -fcaller-saves or -fexpensive-optimizations removed). It works under under valgrind (and does not show any uninitialized variables or memory overwrites). I have debug code like "if (debug) fprintf(stderr, ...);" It works if I set debug to 1. It also works if I go to any of several debug statements and change "if (debug)" to "if (debug || 1)". It seems as if one of the local variables is getting messed up, and either the preparation or clean up after a fprintf() call invalidates the register with the variable or gets a fresh copy from the stack. I suppose that it would be impossible to track down without an example, but if anyone has a similar problem with the combination of 32 bit Intel + -O1 + -fcaller-saves + -fexpensive-optimizations, maybe this comment will add another data point, and if there is a patch, I could try to build it.
next parent reply other threads:[~2021-03-12 4:11 UTC|newest] Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <bug-89965-4@http.gcc.gnu.org/bugzilla/> 2021-03-12 4:11 ` williambader at hotmail dot com [this message] 2021-03-15 0:41 ` williambader at hotmail dot com
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