[llvm-bugs] [Bug 37648] New: wrong code with "opt -loop-rotate -mem2reg -loop-vectorize -instcombine"

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=37648

            Bug ID: 37648
           Summary: wrong code with "opt -loop-rotate -mem2reg
                    -loop-vectorize -instcombine"
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: su at cs.ucdavis.edu
                CC: llvm-bugs at lists.llvm.org

Created attachment 20378
  --> https://bugs.llvm.org/attachment.cgi?id=20378&action=edit
LLVM IR triggering the wrong code

Tested with trunk revision 333708. 

$ clangpolly -v
clang version 7.0.0 (http://llvm.org/git/clang.git
d8cadd200135a319ef1a7ec2b7cabe210cfb3343) (http://llvm.org/git/llvm.git
238f816f4c47e1de89fb4647c67bdfb5fb3da7dc)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/su/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5.4.0
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/6.0.0
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/4.7.4
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
$ 
$ clangpolly -O3 -mllvm -disable-llvm-optzns -c -emit-llvm -o small.bc small.c
$ optpolly -loop-rotate -mem2reg -loop-vectorize -instcombine -o small-opt.bc
small.bc
$ clangpolly small-opt.bc
$ ./a.out
0
$ 
$ clangpolly -O0 small.c; ./a.out
4
$ 


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


int printf (const char *, ...);

unsigned a = 5;

int main ()
{
  int b = 4, c = 0;
  for (; c < 29; ++c)
    {
      int d = -1;
      b &= a % d;
    }
  printf ("%d\n", b);
  return 0;
}

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