[llvm-bugs] [Bug 41509] New: wrong code after running structurizecfg pass

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=41509

            Bug ID: 41509
           Summary: wrong code after running structurizecfg pass
           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 21778
  --> https://bugs.llvm.org/attachment.cgi?id=21778&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

For the following code small.c, after running structurizecfg pass, it will
output wrong result.
-----------------------------------------------------------
#include<stdio.h>
struct {
  int a;
} b;
int c, d;
int main() {

e:
  for (; c <= 1; c++) {
    int f;
    for (; b.a;)
      if (f)
        goto e;
  }
  printf("%d\n",c);
}
-----------------------------------------------------------
$clang small.c -o small1.out && ./small1.out
2
$gcc small.c -o small2.out && ./small2.out
2

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

$opt -jump-threading -licm -loop-unswitch  small.bc -o small-opt1.bc
$clang small-opt1.bc -o small3.out && ./small3.out
2

$opt -structurizecfg small-opt1.bc -o small-opt2.bc
$clang small-opt2.bc -o small4.out && ./small4.out
0

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