[LowerSwitch] Don't let pass manager handle the dependency (#68662)

Some passes has limitation that only support simple terminators:
branch/unreachable/return. Right now, they ask the pass manager to add
LowerSwitch pass to eliminate `switch`. Let's manage such kind of pass
dependency by ourselves. Also add the assertion in the related passes.

1 files changed, 10 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
index 389aab3..05ff4ef 100644
--- a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -2076,3 +2076,13 @@ void llvm::InvertBranch(BranchInst *PBI, IRBuilderBase &Builder) {
   PBI->setCondition(NewCond);
   PBI->swapSuccessors();
 }
+
+bool llvm::hasOnlySimpleTerminator(const Function &F) {
+  for (auto &BB : F) {
+    auto *Term = BB.getTerminator();
+    if (!(isa<ReturnInst>(Term) || isa<UnreachableInst>(Term) ||
+          isa<BranchInst>(Term)))
+      return false;
+  }
+  return true;
+}