[llvm-bugs] [Bug 48873] New: wrong code with "-sroa -gvn -licm -loop-rotate -loop-vectorize"

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=48873

            Bug ID: 48873
           Summary: wrong code with "-sroa -gvn -licm -loop-rotate
                    -loop-vectorize"
           Product: new-bugs
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: suochenyao at 163.com
                CC: htmldeveloper at gmail.com, llvm-bugs at lists.llvm.org

Created attachment 24417
  --> https://bugs.llvm.org/attachment.cgi?id=24417&action=edit
IR that is passed to opt

*******************************************************************************
OS and Platform:
CentOS Linux release 7.8.2003 (Core), x86_64 GNU/Linux
*******************************************************************************
Program:
int printf(const char *, ...);
int a=0;
void b() {
  a = 0;
  for (; a <= 4; a++)
    ;
}
int main() {
  b();
  printf("%d\n", a);
}
*******************************************************************************
clang version:
$ clang -v
clang version 10.0.0 (/home/suocy/src/llvm-dev/llvm/tools/clang
65acf43270ea2894dffa0d0b292b92402f80c8cb) (/home/suocy/src/llvm-dev/llvm
2c4ca6832fa6b306ee6a7010bfb80a3f2596f824)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/suocy/bin/llvm-dev/bin
Found candidate GCC installation:
/opt/rh/devtoolset-7/root/usr/lib/gcc/x86_64-redhat-linux/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/4.8.2
Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/4.8.5
Selected GCC installation:
/opt/rh/devtoolset-7/root/usr/lib/gcc/x86_64-redhat-linux/7
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64
*******************************************************************************
Command Lines:
$ clang -O3 -mllvm -disable-llvm-optzns -c -emit-llvm a.c -o a.bc
$ opt -sroa -gvn -licm -loop-rotate -loop-vectorize a.bc -o a.opt.bc
$ clang a.bc -o a1.o
$ clang a.opt.bc -o a2.o
$ ./a1.o
5
$ ./a2.o
15

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