Bail out jump threading on indirect branches

llvm/lib/Transforms/Utils/Local.cpp

@@ -1028,7 +1028,14 @@ CanRedirectPredsOfEmptyBBToSucc(BasicBlock *BB, BasicBlock *Succ,
   if (!BB->hasNPredecessorsOrMore(2))
     return false;
 
-  // Get single common predecessors of both BB and Succ
+  if (any_of(BBPreds, [](const BasicBlock *Pred) {
+        return isa<PHINode>(Pred->begin()) &&
+               isa<IndirectBrInst>(Pred->getTerminator());
+      }))
+    return false;
+
+  // Get the single common predecessor of both BB and Succ. Return false
+  // when there are more than one common predecessors.
   for (BasicBlock *SuccPred : SuccPreds) {
     if (BBPreds.count(SuccPred)) {
       if (CommonPred)
@@ -1133,7 +1140,7 @@ 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 +1,104 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt < %s -passes=simplifycfg -S | FileCheck %s
+
+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"
+
+define dso_local noundef i32 @main() {
+; CHECK-LABEL: define dso_local noundef i32 @main() {
+; CHECK-NEXT:  [[BB:.*]]:
+; CHECK-NEXT:    [[ALLOCA:%.*]] = alloca [2 x ptr], align 16
+; CHECK-NEXT:    store ptr blockaddress(@main, %[[BB4:.*]]), ptr [[ALLOCA]], align 16, !tbaa [[TBAA0:![0-9]+]]
+; CHECK-NEXT:    [[GETELEMENTPTR:%.*]] = getelementptr inbounds [2 x ptr], ptr [[ALLOCA]], i64 0, i64 1
+; CHECK-NEXT:    store ptr blockaddress(@main, %[[BB10:.*]]), ptr [[GETELEMENTPTR]], align 8, !tbaa [[TBAA0]]
+; CHECK-NEXT:    br label %[[BB1:.*]]
+; CHECK:       [[BB1]]:
+; CHECK-NEXT:    [[PHI:%.*]] = phi i32 [ 0, %[[BB]] ], [ [[PHI8:%.*]], %[[BB7:.*]] ]
+; CHECK-NEXT:    [[PHI2:%.*]] = phi i32 [ 0, %[[BB]] ], [ [[PHI9:%.*]], %[[BB7]] ]
+; CHECK-NEXT:    switch i32 [[PHI]], label %[[BB7]] [
+; CHECK-NEXT:      i32 0, label %[[BB12:.*]]
+; CHECK-NEXT:      i32 1, label %[[BB4]]
+; CHECK-NEXT:      i32 2, label %[[BB6:.*]]
+; CHECK-NEXT:    ]
+; CHECK:       [[BB4]]:
+; CHECK-NEXT:    [[PHI5:%.*]] = phi i32 [ [[PHI13:%.*]], %[[BB12]] ], [ [[PHI2]], %[[BB1]] ]
+; CHECK-NEXT:    br label %[[BB7]]
+; CHECK:       [[BB6]]:
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @foo(i32 noundef [[PHI2]])
+; CHECK-NEXT:    [[ADD:%.*]] = add nsw i32 [[PHI2]], 1
+; CHECK-NEXT:    br label %[[BB12]]
+; CHECK:       [[BB7]]:
+; CHECK-NEXT:    [[PHI8]] = phi i32 [ [[PHI]], %[[BB1]] ], [ 2, %[[BB4]] ]
+; CHECK-NEXT:    [[PHI9]] = phi i32 [ [[PHI2]], %[[BB1]] ], [ [[PHI5]], %[[BB4]] ]
+; CHECK-NEXT:    br label %[[BB1]], !llvm.loop [[LOOP4:![0-9]+]]
+; CHECK:       [[BB10]]:
+; CHECK-NEXT:    [[CALL11:%.*]] = call i32 @foo(i32 noundef [[PHI13]])
+; CHECK-NEXT:    ret i32 0
+; CHECK:       [[BB12]]:
+; CHECK-NEXT:    [[PHI13]] = phi i32 [ [[ADD]], %[[BB6]] ], [ [[PHI2]], %[[BB1]] ]
+; CHECK-NEXT:    [[SEXT:%.*]] = sext i32 [[PHI13]] to i64
+; CHECK-NEXT:    [[GETELEMENTPTR14:%.*]] = getelementptr inbounds [2 x ptr], ptr [[ALLOCA]], i64 0, i64 [[SEXT]]
+; CHECK-NEXT:    [[LOAD:%.*]] = load ptr, ptr [[GETELEMENTPTR14]], align 8, !tbaa [[TBAA0]]
+; CHECK-NEXT:    indirectbr ptr [[LOAD]], [label %[[BB4]], label %bb10]
+;
+bb:
+  %alloca = alloca [2 x ptr], align 16
+  store ptr blockaddress(@main, %bb4), ptr %alloca, align 16, !tbaa !0
+  %getelementptr = getelementptr inbounds [2 x ptr], ptr %alloca, i64 0, i64 1
+  store ptr blockaddress(@main, %bb10), ptr %getelementptr, align 8, !tbaa !0
+  br label %bb1
+
+bb1:                                              ; preds = %bb7, %bb
+  %phi = phi i32 [ 0, %bb ], [ %phi8, %bb7 ]
+  %phi2 = phi i32 [ 0, %bb ], [ %phi9, %bb7 ]
+  switch i32 %phi, label %bb7 [
+  i32 0, label %bb3
+  i32 1, label %bb4
+  i32 2, label %bb6
+  ]
+
+bb3:                                              ; preds = %bb1
+  br label %bb12
+
+bb4:                                              ; preds = %bb12, %bb1
+  %phi5 = phi i32 [ %phi13, %bb12 ], [ %phi2, %bb1 ]
+  br label %bb7
+
+bb6:                                              ; preds = %bb1
+  %call = call i32 @foo(i32 noundef %phi2)
+  %add = add nsw i32 %phi2, 1
+  br label %bb12
+
+bb7:                                              ; preds = %bb4, %bb1
+  %phi8 = phi i32 [ %phi, %bb1 ], [ 2, %bb4 ]
+  %phi9 = phi i32 [ %phi2, %bb1 ], [ %phi5, %bb4 ]
+  br label %bb1, !llvm.loop !4
+
+bb10:                                             ; preds = %bb12
+  %call11 = call i32 @foo(i32 noundef %phi13)
+  ret i32 0
+
+bb12:                                             ; preds = %bb6, %bb3
+  %phi13 = phi i32 [ %add, %bb6 ], [ %phi2, %bb3 ]
+  %sext = sext i32 %phi13 to i64
+  %getelementptr14 = getelementptr inbounds [2 x ptr], ptr %alloca, i64 0, i64 %sext
+  %load = load ptr, ptr %getelementptr14, align 8, !tbaa !0
+  indirectbr ptr %load, [label %bb4, label %bb10]
+}
+
+declare i32 @foo(i32)
+
+!0 = !{!1, !1, i64 0}
+!1 = !{!"any pointer", !2, i64 0}
+!2 = !{!"omnipotent char", !3, i64 0}
+!3 = !{!"Simple C++ TBAA"}
+!4 = !{!5, !5, i64 0}
+!5 = !{!"int", !2, i64 0}
+;.
+; CHECK: [[TBAA0]] = !{[[META1:![0-9]+]], [[META1]], i64 0}
+; CHECK: [[META1]] = !{!"any pointer", [[META2:![0-9]+]], i64 0}
+; CHECK: [[META2]] = !{!"omnipotent char", [[META3:![0-9]+]], i64 0}
+; CHECK: [[META3]] = !{!"Simple C++ TBAA"}
+; CHECK: [[LOOP4]] = !{[[META5:![0-9]+]], [[META5]], i64 0}
+; CHECK: [[META5]] = !{!"int", [[META2]], i64 0}
+;.