llvm-reduce: Fix assert on invokes with catchswitch (#111838)

This is the minimal change to avoid the assert. There's an API flaw in
invoke instructions where getLandingPad assumes all invoke unwind
blocks have landingpads, when some have catchswitch instead.

Fixes #111817

Author: arsenm

llvm/test/tools/llvm-reduce/issue111817-catchswitch-assert.ll

@@ -0,0 +1,53 @@
+; RUN: llvm-reduce -abort-on-invalid-reduction --delta-passes=basic-blocks --test FileCheck --test-arg --check-prefixes=CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
+; RUN: FileCheck --check-prefix=CHECK-FINAL %s < %t
+
+; Make sure there's no assertion for invoke destinations that don't
+; use landingpad (and use catchswitch instead)
+
+; CHECK-INTERESTINGNESS: invoke
+
+; CHECK-FINAL: bb:
+; CHECK-FINAL-NEXT: invoke void @llvm.seh.try.begin()
+; CHECK-FINAL-NEXT:   to label %bb7 unwind label %bb1
+; CHECK-FINAL: bb1:
+; CHECK-FINAL-NEXT: %i = catchswitch within none [label %bb2] unwind to caller
+
+; CHECK-FINAL: bb2:
+; CHECK-FINAL-NEXT: %i3 = catchpad within %i [ptr null]
+; CHECK-FINAL-NEXT: ret ptr null
+
+; CHECK-FINAL-NOT: bb4
+; CHECK-FINAL-NOT: bb5
+
+; CHECK-FINAL: bb7:
+; CHECK-FINAL-NEXT: ret ptr null
+define ptr @func() personality ptr @__C_specific_handler {
+bb:
+  invoke void @llvm.seh.try.begin()
+          to label %bb7 unwind label %bb1
+
+bb1:                                              ; preds = %bb
+  %i = catchswitch within none [label %bb2] unwind to caller
+
+bb2:                                              ; preds = %bb1
+  %i3 = catchpad within %i [ptr null]
+  catchret from %i3 to label %bb4
+
+bb4:                                              ; preds = %bb2
+  invoke void @llvm.seh.try.end()
+          to label %bb7 unwind label %bb5
+
+bb5:                                              ; preds = %bb4
+  %i6 = cleanuppad within none []
+  cleanupret from %i6 unwind to caller
+
+bb7:                                              ; preds = %bb4, %bb
+  ret ptr null
+}
+
+declare void @llvm.seh.try.begin() #0
+declare void @llvm.seh.try.end() #0
+declare i32 @__C_specific_handler(...)
+
+attributes #0 = { nounwind willreturn memory(write) }
+

llvm/tools/llvm-reduce/deltas/ReduceBasicBlocks.cpp

@@ -45,12 +45,21 @@ static void replaceBranchTerminator(BasicBlock &BB,
   if (ChunkSuccessors.size() == Term->getNumSuccessors())
     return;
 
+  // TODO: Handle these without failing verifier.
+  if (isa<CatchSwitchInst>(Term))
+    return;
+
   bool IsBranch = isa<BranchInst>(Term);
   if (InvokeInst *Invoke = dyn_cast<InvokeInst>(Term)) {
-    LandingPadInst *LP = Invoke->getLandingPadInst();
+    BasicBlock *UnwindDest = Invoke->getUnwindDest();
+    Instruction *LP = UnwindDest->getFirstNonPHI();
+
     // Remove landingpad instruction if the containing block isn't used by other
     // invokes.
-    if (none_of(LP->getParent()->users(), [Invoke](User *U) {
+
+    // TODO: Handle catchswitch, catchpad, catchret, and cleanupret
+    if (isa<LandingPadInst>(LP) &&
+        none_of(UnwindDest->users(), [Invoke](User *U) {
           return U != Invoke && isa<InvokeInst>(U);
         })) {
       LP->replaceAllUsesWith(getDefaultValue(LP->getType()));