[llvm-bugs] [Bug 42860] New: loop-instsimplify makes function broken with "opt -sroa -loop-rotate -jump-threading -lcssa -loop-instsimplify"

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=42860

            Bug ID: 42860
           Summary: loop-instsimplify makes function broken with "opt
                    -sroa -loop-rotate -jump-threading -lcssa
                    -loop-instsimplify"
           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 22329
  --> https://bugs.llvm.org/attachment.cgi?id=22329&action=edit
.bc file of the source code

$clang -v
clang version 10.0.0 (trunk 367076)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/jack-zhou/Documents/llvm/llvm_truck/llvm2/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/7.4.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.4.0
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64

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

$opt -sroa -loop-rotate -jump-threading -lcssa  -loop-instsimplify small.bc -o
small-opt.bc
PHI nodes must have at least one entry.  If the block is dead, the PHI should
be removed!
  %h.3.lcssa40 = phi i16 
in function g
LLVM ERROR: Broken function found, compilation aborted!

---------------------------------------------------------
int a, b, c, e, f;
char d;
void g() {
  short h = 0;
  int i, j;
k:
  d = h;
l:
  for (; 0; c) {
    int m;
    int *n[10][8][3] = {&i, &m, &b, 0, &b, 0, 0, 0, &j, &b, &a, &a};
    long o[8];
    for (; e;)
      for (; f; f++)
        o[f];
    for (; 0;) {
      int p;
      for (;; e)
        if (p)
          goto k;
    }
    if (h)
      break;
    h = 0;
  }
  goto l;
}

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