Bail out jump threading on indirect branches

The bug was introduced by #68473

Author: hiraditya

llvm/lib/Transforms/Utils/Local.cpp

@@ -868,6 +868,8 @@ CanPropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ,
 
   LLVM_DEBUG(dbgs() << "Looking to fold " << BB->getName() << " into "
                     << Succ->getName() << "\n");
+  if (isa<IndirectBrInst>(Succ->getTerminator()))
+    return false;
   // Shortcut, if there is only a single predecessor it must be BB and merging
   // is always safe
   if (Succ->getSinglePredecessor())
@@ -1029,11 +1031,12 @@ CanRedirectPredsOfEmptyBBToSucc(BasicBlock *BB, BasicBlock *Succ,
     return false;
 
   // Get single common predecessors of both BB and Succ
+  // TODO: Replace this with a proper `set intersect` algorithm
   for (BasicBlock *SuccPred : SuccPreds) {
     if (BBPreds.count(SuccPred)) {
+      CommonPred = SuccPred;
       if (CommonPred)
         return false;
-      CommonPred = SuccPred;
     }
   }
 
@@ -1133,7 +1136,7 @@ bool llvm::TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB,
 
   bool BBKillable = CanPropagatePredecessorsForPHIs(BB, Succ, BBPreds);
 
-  // Even if we can not fold bB into Succ, we may be able to redirect the
+  // Even if we can not fold BB into Succ, we may be able to redirect the
   // predecessors of BB to Succ.
   bool BBPhisMergeable =
       BBKillable ||

llvm/test/Transforms/SimplifyCFG/switch-branch-fold-indirectbr-102351.ll

@@ -0,0 +1,82 @@
+; RUN: opt < %s -passes=simplifycfg -S | FileCheck %s
+
+; CHECK: switch i32 %state.0, label %sw.epilog
+; CHECK-NEXT: i32 0, label %sw.bb
+; CHECK-NEXT: i32 1, label %VM__OP_1
+; CHECK-NEXT: i32 2, label %sw.bb4
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@.str = private unnamed_addr constant [23 x i8] c"OP_1:(instruction=%d)\0A\00", align 1
+@.str.1 = private unnamed_addr constant [28 x i8] c"TERMINATE:(instruction=%d)\0A\00", align 1
+
+; Function Attrs: mustprogress norecurse uwtable
+define dso_local noundef i32 @main() #0 {
+entry:
+  %bytecode = alloca [2 x ptr], align 16
+  store ptr blockaddress(@main, %VM__OP_1), ptr %bytecode, align 16, !tbaa !5
+  %arrayidx1 = getelementptr inbounds [2 x ptr], ptr %bytecode, i64 0, i64 1
+  store ptr blockaddress(@main, %VM__TERMINATE), ptr %arrayidx1, align 8, !tbaa !5
+  br label %while.body
+
+while.body:                                       ; preds = %entry, %sw.epilog
+  %state.0 = phi i32 [ 0, %entry ], [ %state.1, %sw.epilog ]
+  %index.0 = phi i32 [ 0, %entry ], [ %index.2, %sw.epilog ]
+  switch i32 %state.0, label %sw.epilog [
+    i32 0, label %sw.bb
+    i32 1, label %VM__OP_1
+    i32 2, label %sw.bb4
+  ]
+
+sw.bb:                                            ; preds = %while.body
+  br label %indirectgoto
+
+VM__OP_1:                                         ; preds = %while.body, %indirectgoto
+  %index.1 = phi i32 [ %index.3, %indirectgoto ], [ %index.0, %while.body ]
+  br label %sw.epilog
+
+sw.bb4:                                           ; preds = %while.body
+  %call = call i32 (ptr, ...) @printf(ptr noundef nonnull dereferenceable(1) @.str, i32 noundef %index.0)
+  %inc = add nsw i32 %index.0, 1
+  br label %indirectgoto
+
+sw.epilog:                                        ; preds = %while.body, %VM__OP_1
+  %state.1 = phi i32 [ %state.0, %while.body ], [ 2, %VM__OP_1 ]
+  %index.2 = phi i32 [ %index.0, %while.body ], [ %index.1, %VM__OP_1 ]
+  br label %while.body, !llvm.loop !9
+
+VM__TERMINATE:                                    ; preds = %indirectgoto
+  %call7 = call i32 (ptr, ...) @printf(ptr noundef nonnull dereferenceable(1) @.str.1, i32 noundef %index.3)
+  ret i32 0
+
+indirectgoto:                                     ; preds = %sw.bb4, %sw.bb
+  %index.3 = phi i32 [ %inc, %sw.bb4 ], [ %index.0, %sw.bb ]
+  %idxprom.pn = sext i32 %index.3 to i64
+  %indirect.goto.dest.in = getelementptr inbounds [2 x ptr], ptr %bytecode, i64 0, i64 %idxprom.pn
+  %indirect.goto.dest = load ptr, ptr %indirect.goto.dest.in, align 8, !tbaa !5
+  indirectbr ptr %indirect.goto.dest, [label %VM__OP_1, label %VM__TERMINATE]
+}
+declare i32 @printf(ptr noundef, ...) #1
+
+attributes #0 = { mustprogress norecurse uwtable "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
+attributes #1 = { "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
+
+!llvm.module.flags = !{!0, !1, !2, !3}
+!llvm.ident = !{!4}
+
+!0 = !{i32 1, !"wchar_size", i32 4}
+!1 = !{i32 8, !"PIC Level", i32 2}
+!2 = !{i32 7, !"PIE Level", i32 2}
+!3 = !{i32 7, !"uwtable", i32 2}
+!4 = !{!"clang version 18.0.0git (https://github.com/llvm/llvm-project.git 67782d2de5ea9c8653b8f0110237a3c355291c0e)"}
+!5 = !{!6, !6, i64 0}
+!6 = !{!"any pointer", !7, i64 0}
+!7 = !{!"omnipotent char", !8, i64 0}
+!8 = !{!"Simple C++ TBAA"}
+!9 = !{!10, !10, i64 0}
+!10 = !{!"int", !7, i64 0}
+!11 = distinct !{!11, !12, !13}
+!12 = !{!"llvm.loop.mustprogress"}
+!13 = !{!"llvm.loop.unroll.disable"}
+