[clang] [clang][dataflow] Refactor processing of terminator element (PR #84499)

[via cfe-commits]

================
@@ -337,26 +274,33 @@ computeBlockInputState(const CFGBlock &Block, AnalysisContext &AC) {
         AC.BlockStates[Pred->getBlockID()];
     if (!MaybePredState)
       continue;
-
-    if (AC.Analysis.builtinOptions()) {
-      if (const Stmt *PredTerminatorStmt = Pred->getTerminatorStmt()) {
-        // We have a terminator: we need to mutate an environment to describe
-        // when the terminator is taken. Copy now.
+    const TypeErasedDataflowAnalysisState &PredState = *MaybePredState;
+
+    if (const Stmt *PredTerminatorStmt = Pred->getTerminatorStmt()) {
----------------
martinboehme wrote:

I'd suggest doing the shorter case first, so this longer case can be indented less:

```cxx
  const Stmt *PredTerminatorStmt = Pred->getTerminatorStmt();
  if (PredTerminatorStmt == nullptr) {
    Builder.addUnowned(PredState);
    continue;
  }
```

Even better, introduce a short function `getTerminatorCondition()` that can handle a null argument:

```cxx
const Expr *getTerminatorCondition(const Stmt *TerminatorStmt) {
  if (TerminatorStmt == nullptr) return nullptr;
  return TerminatorVisitor().Visit(TerminatorStmt);
}
```

Then you can do this:

```cxx
  const Expr *TerminatorCond = getTerminatorCondition(Pred->getTerminatorStmt());
  if (TerminatorCond == nullptr) {
    Builder.addUnowned(PredState);
    continue;
  }
```

https://github.com/llvm/llvm-project/pull/84499