[llvm] [BPF] Remove unused weak symbol __bpf_trap (PR #166003)

[Jordan Rupprecht via llvm-commits]

================
@@ -160,6 +170,20 @@ bool BPFAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
 }
 
 void BPFAsmPrinter::emitInstruction(const MachineInstr *MI) {
+  if (MI->isCall()) {
+    for (const MachineOperand &Op : MI->operands()) {
+      if (Op.isGlobal()) {
+        if (const GlobalValue *GV = Op.getGlobal())
+          if (GV->getName() == BPF_TRAP)
+            SawTrapCall = true;
+      } else if (Op.isSymbol()) {
+        if (const MCSymbol *Sym = Op.getMCSymbol())
----------------
rupprecht wrote:

This will always fire an assertion:

```cc
  MCSymbol *getMCSymbol() const {
    assert(isMCSymbol() && "Wrong MachineOperand accessor");
    return Contents.Sym;
  }
```

But `isMCSymbol()` is always false since `isSymbol()` is true instead.

What's the right fix?

https://github.com/llvm/llvm-project/pull/166003