[llvm] [AMDGPU][FixIrreducible][UnifyLoopExits] Support callbr with inline-asm (PR #149308)

[Matt Arsenault via llvm-commits]

================
@@ -266,17 +329,32 @@ static bool fixIrreducible(Cycle &C, CycleInfo &CI, DominatorTree &DT,
   }
 
   for (BasicBlock *P : Predecessors) {
-    auto *Branch = cast<BranchInst>(P->getTerminator());
-    BasicBlock *Succ0 = Branch->getSuccessor(0);
-    Succ0 = C.contains(Succ0) ? Succ0 : nullptr;
-    BasicBlock *Succ1 =
-        Branch->isUnconditional() ? nullptr : Branch->getSuccessor(1);
-    Succ1 = Succ1 && C.contains(Succ1) ? Succ1 : nullptr;
-    CHub.addBranch(P, Succ0, Succ1);
-
-    LLVM_DEBUG(dbgs() << "Added external branch: " << P->getName() << " -> "
-                      << (Succ0 ? Succ0->getName() : "") << " "
-                      << (Succ1 ? Succ1->getName() : "") << "\n");
+    if (BranchInst *Branch = dyn_cast<BranchInst>(P->getTerminator()); Branch) {
+      BasicBlock *Succ0 = Branch->getSuccessor(0);
+      Succ0 = C.contains(Succ0) ? Succ0 : nullptr;
+      BasicBlock *Succ1 =
+          Branch->isUnconditional() ? nullptr : Branch->getSuccessor(1);
+      Succ1 = Succ1 && C.contains(Succ1) ? Succ1 : nullptr;
+      CHub.addBranch(P, Succ0, Succ1);
+
+      LLVM_DEBUG(dbgs() << "Added external branch: " << P->getName() << " -> "
+                        << (Succ0 ? Succ0->getName() : "") << " "
+                        << (Succ1 ? Succ1->getName() : "") << "\n");
+    } else if (CallBrInst *CallBr = dyn_cast<CallBrInst>(P->getTerminator());
+               CallBr) {
+      for (unsigned I = 0; I < CallBr->getNumSuccessors(); ++I) {
+        BasicBlock *Succ = CallBr->getSuccessor(I);
+        if (!C.contains(Succ))
+          continue;
+        BasicBlock *NewSucc = llvm::ControlFlowHub::createCallBrTarget(
+            CallBr, Succ, I, true, &CI, &DTU, LI);
+        CHub.addBranch(NewSucc, Succ);
+        LLVM_DEBUG(dbgs() << "Added external branch: " << NewSucc->getName()
+                          << " -> " << Succ->getName() << "\n");
+      }
+    } else {
+      llvm_unreachable("Unsupported block terminator.");
----------------
arsenm wrote:

```suggestion
      llvm_unreachable("unsupported block terminator");
```

https://github.com/llvm/llvm-project/pull/149308