[llvm] [ControlFlowHub] Add support for switch-based guards (PR #213549)

[via llvm-commits]

================
@@ -279,17 +281,19 @@ static void reconnectPhis(BasicBlock *Out, BasicBlock *GuardBlock,
 
 std::pair<BasicBlock *, bool> ControlFlowHub::finalize(
     DomTreeUpdater *DTU, SmallVectorImpl<BasicBlock *> &GuardBlocks,
-    const StringRef Prefix, std::optional<unsigned> MaxControlFlowBooleans) {
+    const StringRef Prefix, std::optional<unsigned> MaxControlFlowBooleans,
+    bool SwitchGuards) {
 #ifndef NDEBUG
   SmallPtrSet<BasicBlock *, 8> Incoming;
 #endif
   SetVector<BasicBlock *> Outgoing;
 
   for (auto [BB, Succ0, Succ1] : Branches) {
 #ifndef NDEBUG
-    assert(
-        (Incoming.insert(BB).second || isa<CallBrInst>(BB->getTerminator())) &&
-        "Duplicate entry for incoming block.");
+    assert((Incoming.insert(BB).second ||
+            isa<CallBrInst>(BB->getTerminator()) ||
+            isa<SwitchInst>(BB->getTerminator())) &&
----------------
hertelukas wrote:

Not sure if this is necessary - `isa<CallBrInst>` and `isa<SwitchInst>` should never evaluate to true:

```
/// Limitations:
/// -----------
/// 1. This assumes that all terminators in the CFG are direct branches (the
///    "br" instruction). The presence of any other control flow such as
///    indirectbr, switch or callbr will cause an assert.
```

And `FixIrreducible` and `UnifyLoopExits` adhere to that by running `SplitMultiBrEdge` first.



https://github.com/llvm/llvm-project/pull/213549