[llvm-bugs] [Bug 35240] New: Wrong constant folding

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=35240

            Bug ID: 35240
           Summary: Wrong constant folding
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: ishiura-compiler at ml.kwansei.ac.jp
                CC: llvm-bugs at lists.llvm.org

LLVM + clang 6.0 for x86_64 miscompiles the following code.

% cat test.c
volatile int buff = 0;
void PRINTF(const int* s)
{
  while(*s++) buff = *s;
}

char a = 0;
char b = 0;
short c = 0;
int d = 0;
int e = 0;

int main (void)
{
  volatile short f = 1;
  volatile int g = 1;
  int h = ( 1 << c ) & 3;
  a = 0 == g;
  int i = 1 == g;
  volatile int j = ((long)3>>g)%3;
  volatile int k = (1*i)>>c;
  c = a|f;
  e = 3<<a;
  b = d*i;
  int l = (3>>a)/3;
  if (h != 1) { PRINTF((const int*)&h); }
  if (c != 1) __builtin_abort();
  if (l != 1) __builtin_abort();
  return 0;
}

% clang-6.0 -O1 test.c
% ./a.out
zsh: abort (core dumped)  ./a.out
% clang-6.0 -O2 test.c
% ./a.out
zsh: abort (core dumped)  ./a.out
% clang-6.0 -O3 test.c
% ./a.out
zsh: abort (core dumped)  ./a.out
% clang-6.0 -Os test.c
% ./a.out
zsh: abort (core dumped)  ./a.out
% clang-6.0 -v
clang version 6.0.0 (trunk 317078)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.5
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
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.4.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.0.0
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.4.0
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64

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