[IROutliner] Crash due to missing GVN

[lanza]

When building the following source:

# 2 "" 3
typedef a;
typedef struct {
  int b;
  a c;
  a d
} e;
typedef struct {
  int f;
  e g
} h;
typedef struct {
  h ac;
  void *i
} j;
typedef (*k)();
typedef (*l)();
typedef (*m)();
n;
typedef (*ad)();
typedef (*o)();
p(j);
j q();
r() {
  j s = q();
  if (p(s)) {
    a t = s.ac.f ? s.ac.g.d : s.ac.g.c;
    if (t) {
      k a = s.i;
      a();
    }
  }
}
u() {
  j s = q();
  if (p(s)) {
    a t = s.ac.f ? s.ac.g.d : s.ac.g.c;
    if (t) {
      l b = s.i;
      b(u);
    }
  }
}
v() {
  j s = q();
  if (p(s)) {
    a t = s.ac.f ? s.ac.g.d : s.ac.g.c;
    if (t) {
      m c = s.i;
      c(n);
    }
  }
}
w() {
  j s = q();
  if (p(s)) {
    a t = s.ac.f ? s.ac.g.d : s.ac.g.c;
    if (t) {
      ad d = s.i;
      return d(t);
    }
  }
  return 0;
}
x() {
  j s = q();
  if (p(s)) {
    a t = s.ac.f ? s.ac.g.d : s.ac.g.c;
    if (t) {
      o e = s.i;
      return e(t, 0);
    }
  }
  return 0;
}

with the following flags:

-mthumb
-target
armv7-none-linux-androideabi19
-g3
-mllvm
-ir-outliner
-Oz
-ftrivial-auto-var-init=zero
-enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang
-c
here2.c

We reach a crash here: https://github.com/llvm/llvm-project/blob/main/llvm/lib/Transforms/IPO/IROutliner.cpp#L190.

Here is a link to a Godbolt repro: https://godbolt.org/z/7Kzf37P4b

[lanza]

cc @ornata @AndrewLitteken

BTW I have no need for this to be fixed any time soon. We aren't planning to use it for this code (at least not yet?). Just known about it for awhile and figured I'd share the reduced crash.

[dcci]

Proposed fix in #72945

[lanza]

Can confirm that this is the fix for the previously observed crash!

[EugeneZelenko]

@lanza: Fix is not merged yet.