[llvm-bugs] [Bug 41720] New: loop-vectorize produces wrong code with "opt -gvn -licm -loop-rotate -loop-vectorize"

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=41720

            Bug ID: 41720
           Summary: loop-vectorize produces wrong code with "opt -gvn
                    -licm -loop-rotate -loop-vectorize"
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: cszide at 163.com
                CC: llvm-bugs at lists.llvm.org

Created attachment 21880
  --> https://bugs.llvm.org/attachment.cgi?id=21880&action=edit
.bc file of the source code

$clang -v
clang version 9.0.0 (trunk 355281)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/jack-zhou/Documents/llvm/llvm_truck/llvm/build4/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.3.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.3.0
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64

$clang -O3 -c -emit-llvm  -mllvm -disable-llvm-optzns small.c

$clang small.bc -o small1.out && ./small1.out
9

$opt -gvn -licm -loop-rotate -loop-vectorize   small.bc -o small-opt.bc

$clang small-opt.bc -o small2.out && ./small2.out
15

without loop-vectorize, the result is correct.
$opt -gvn -licm -loop-rotate small.bc -o small-opt1.bc

$clang small-opt1.bc -o small3.out && ./small3.out
9

------------------------------------
#include<stdio.h>
int a=0;
int d() {
  int e = 2;
  for (a = 0; a <= 8; a++)
    ;
  return e;
}
void main() {
  int f = 0;
  d();
  printf("%d\n",a);
}

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