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List:       gcc-bugs
Subject:    [Bug tree-optimization/69097] New: wrong code at -O1 and above on x86_64-linux-gnu
From:       "su at cs dot ucdavis.edu" <gcc-bugzilla () gcc ! gnu ! org>
Date:       2015-12-31 1:58:58
Message-ID: bug-69097-4 () http ! gcc ! gnu ! org/bugzilla/
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69097

            Bug ID: 69097
           Summary: wrong code at -O1 and above on x86_64-linux-gnu
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu
  Target Milestone: ---

The current gcc trunk mis-compiles the following code on x86_64-linux-gnu at
-O1 and above in both 32-bit and 64-bit modes.

This is a regression from 5.3.x. 


$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/6.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-trunk/configure --prefix=/usr/local/gcc-trunk
--enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
gcc version 6.0.0 20151229 (experimental) [trunk revision 231989] (GCC) 
$ 
$ gcc-trunk -O0 small.c; ./a.out
$ gcc-5.3 -O1 small.c; ./a.out
$ 
$ gcc-trunk -O1 small.c
$ ./a.out
Floating point exception (core dumped)
$ 


-------------------------------


int a, b;
unsigned int c;

int
main ()
{
  int d = b;
  b = ~(~a + (~d | b));
  a = ~(~c >> b);
  c = a % b;
  return 0;
}=
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