From c2f40066bbceb15e73e5c4df97d2d115f8a36e58 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Sat, 14 Aug 2010 00:43:09 +0000
Subject: [PATCH] LoopSimplify shouldn't split loop backedges that use
 indirectbr. PR7867.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111061 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Utils/LoopSimplify.cpp         |  5 +++
 .../LoopSimplify/indirectbr-backedge.ll       | 35 +++++++++++++++++++
 2 files changed, 40 insertions(+)
 create mode 100644 test/Transforms/LoopSimplify/indirectbr-backedge.ll

diff --git a/lib/Transforms/Utils/LoopSimplify.cpp b/lib/Transforms/Utils/LoopSimplify.cpp
index 16902ff9150..fee7f081333 100644
--- a/lib/Transforms/Utils/LoopSimplify.cpp
+++ b/lib/Transforms/Utils/LoopSimplify.cpp
@@ -622,6 +622,11 @@ LoopSimplify::InsertUniqueBackedgeBlock(Loop *L, BasicBlock *Preheader) {
   std::vector<BasicBlock*> BackedgeBlocks;
   for (pred_iterator I = pred_begin(Header), E = pred_end(Header); I != E; ++I){
     BasicBlock *P = *I;
+
+    // Indirectbr edges cannot be split, so we must fail if we find one.
+    if (isa<IndirectBrInst>(P->getTerminator()))
+      return 0;
+
     if (P != Preheader) BackedgeBlocks.push_back(P);
   }
 
diff --git a/test/Transforms/LoopSimplify/indirectbr-backedge.ll b/test/Transforms/LoopSimplify/indirectbr-backedge.ll
new file mode 100644
index 00000000000..ca6e47fcecd
--- /dev/null
+++ b/test/Transforms/LoopSimplify/indirectbr-backedge.ll
@@ -0,0 +1,35 @@
+; RUN: opt -loopsimplify -S < %s | FileCheck %s
+
+; LoopSimplify shouldn't split loop backedges that use indirectbr.
+
+; CHECK: bb1:                                              ; preds = %bb5, %bb
+; CHECK-NEXT: indirectbr
+
+; CHECK: bb5:                                              ; preds = %bb1
+; CHECK-NEXT: br label %bb1{{$}}
+
+define void @foo(i8* %p) nounwind {
+bb:
+  br label %bb1
+
+bb1:                                              ; preds = %bb5, %bb1, %bb
+  indirectbr i8* %p, [label %bb6, label %bb7, label %bb1, label %bb2, label %bb3, label %bb5, label %bb4]
+
+bb2:                                              ; preds = %bb1
+  ret void
+
+bb3:                                              ; preds = %bb1
+  ret void
+
+bb4:                                              ; preds = %bb1
+  ret void
+
+bb5:                                              ; preds = %bb1
+  br label %bb1
+
+bb6:                                              ; preds = %bb1
+  ret void
+
+bb7:                                              ; preds = %bb1
+  ret void
+}