The code in the test is causing a crash in `SIInstrInfo.cpp`
`fixImplicitOperands()` in `MI.implicit_operands()`:
```
for (auto &Op : MI.implicit_operands()) {
```
MachineInstr.h:
```
mop_range implicit_operands() {
=> return operands_impl().drop_front(getNumExplicitOperands());
}
```
We are trying to drop 1 operand from the operands of MI which are 0.
By early returning we are no longer crashing at that point and we are
getting a more meaningful error message:
```
*** Bad machine code: Too few operands ***
- function: missing_operand_crash
- basic block: %bb.0 (0x5a9d30ced988)
- instruction: S_WAITCNT_DEPCTR
1 operands expected, but 0 given.
```
The code is still crashing at a different location, but at least we are
getting an error message.
21dad8e5cc