[llvm-bugs] [Bug 26350] New: wrong code on x86_64-linux-gnu at -O1 and above in 32-bit mode

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=26350

            Bug ID: 26350
           Summary: wrong code on x86_64-linux-gnu at -O1 and above in
                    32-bit mode
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: chengniansun at gmail.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

The following code is miscompiled by the trunk in 32-bit mode at -O1 and above.
It also affects clang-3.2 and later versions.

The compiled executable non-deterministically outputs "l_1845=0".

$: clang-trunk  -v
clang version 3.9.0 (trunk 258824) (llvm/trunk 258823)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.9.3
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5.3.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.3.0
Found candidate GCC installation:
/usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.6.3
Found candidate GCC installation:
/usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.7.4
Found candidate GCC installation:
/usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.8.2
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64
$: 
$: clang-trunk -w -m32 -O0 small.c 
$: (for i in {1..1000} ; do ./a.out ; done) | wc -l
1000
$: clang-trunk -w -m32 -O1 small.c 
$: (for i in {1..1000} ; do ./a.out ; done) | wc -l
474
$: clang-trunk -w -m32 -O2 small.c 
$: (for i in {1..1000} ; do ./a.out ; done) | wc -l
502
$: clang-trunk -w -m32 -O3 small.c 
$: (for i in {1..1000} ; do ./a.out ; done) | wc -l
516
$: 
$: cat small.c
int printf(const char*, ...);
volatile char a, h;
long long b;
int d;
long long fn1_p;
int main() {
  unsigned j = 9, m;
  int k = -1L, o;
  long long n = -1L;
  o = m = ~fn1_p;
  b = -(-n ^ (j | d)) * ~ - k;
  if (m > b)
    printf("l_1845=%llu\n", (long long)h);
  o || a;
  return 0;
}
$:

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