[llvm] Bail out jump threading on indirect branches (PR #103688)

[via llvm-commits]

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@@ -1028,7 +1028,14 @@ CanRedirectPredsOfEmptyBBToSucc(BasicBlock *BB, BasicBlock *Succ,
   if (!BB->hasNPredecessorsOrMore(2))
     return false;
 
-  // Get single common predecessors of both BB and Succ
+  if (any_of(BBPreds, [](const BasicBlock *Pred) {
+        return isa<PHINode>(Pred->begin()) &&
----------------
hiraditya wrote:

do you mind sharing your test case? I tried replacing switch with if-else and moving the check to a function parameter but didn't get a miscompile. https://godbolt.org/z/xvs571nbj

```cpp
#include<stdio.h>
__attribute__((noinline))
int foo(int state) {
  void* bytecode[2];
  bytecode[0] = &&VM__OP_1;
  bytecode[1] = &&VM__TERMINATE;

  //int state = 0;
  int index = 0;

  while (1) {
    if (state==0) {
      goto *bytecode[index];
    }
    if (state == 1) {
      printf("Unreachable\n");
      // NOTE: THIS IS ONLY REACHABLE VIA INDIRECT GOTOS
    VM__OP_1:
      printf("VM__OP_1\n");
      state = 2;
    }
    else if (state== 2) {
      printf("OP_1:(instruction=%d)\n", index);
      index++;
      goto *bytecode[index];
    }
  }

VM__TERMINATE:
  printf("TERMINATE:(instruction=%d)\n", index);
  return 0;
}

int main() {
  foo(0);
  return 0;
}```

https://github.com/llvm/llvm-project/pull/103688