<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/62058>62058</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [SimpleLoopUnswitch] Assertion failed: isa<To>(Val) && "cast<Ty>() argument of incompatible type!
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            c,
            llvm:optimizations
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          kbelochapka
      </td>
    </tr>
</table>

<pre>
    Reproducible:

clang -c -O3 1.c
cat 1.c
```c++
long a;
void *b();
void c() {
 for (;;) {
    a = (long)b();
    if (a < 0)
      return;
 }
}
```
Assertion happens inside of the following code fragment:
```c++
[llvm\lib\Transforms\Scalar\SimpleLoopUnswitch.cpp]
.....
if (Pred == ICmpInst::ICMP_SGE && match(RHS, m_Zero())  {
    // Turn "x >=s 0" into "x <u UMIN_INT"
    Pred = ICmpInst::ICMP_ULT;
    RHS = ConstantInt::get(
        RHS->getContext(),
 APInt::getSignedMinValue(RHS->getType()->getIntegerBitWidth()));
 }
```
More precisely:
```c++
[llvm\include\llvm\IR\DerivedTypes.h]
unsigned Type::getIntegerBitWidth() const {return cast<IntegerType>(this)->getBitWidth();}
...
[llvm\include\llvm\Support\Casting.h]
template <typename To, typename From>
[[nodiscard]] inline decltype(auto) cast(From *Val) {
  assert(isa<To>(Val) && "cast<Ty>() argument of incompatible type!"); ------>>> ASSERTION
  return CastInfo<To, From *>::doCast(Val);
}
```
The assertion happens because the code expects that the RHS variable has an INTEGER type (IntegerTyID) but in reality the variable type is a POINTER (PointerTyID) (ptr null).
The LHS variable is also a POINTER ( %call = tail call ptr (...) @b() )

The code fragment is a part of the following commit:

```
commit 5d10753314ed58e1f55d41118c8f082c5fc7b2d7
Author: Max Kazantsev <mkazantsev@azul.com>
Date:   Fri Feb 10 11:56:08 2023 +0700
 [SimpleLoopUnswitch] Inject loop-invariant conditions and unswitch them when it's profitable
    Based on https://discourse.llvm.org/t/rfc-inject-invariant-conditions-to-loops-to-enable-unswitching-and-constraint-elimination
```

</pre>
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