diff --git a/lib/Transforms/Utils/LoopSimplify.cpp b/lib/Transforms/Utils/LoopSimplify.cpp
index 904c6fee45f..437626552b2 100644
--- a/lib/Transforms/Utils/LoopSimplify.cpp
+++ b/lib/Transforms/Utils/LoopSimplify.cpp
@@ -99,7 +99,8 @@ namespace {
     bool ProcessLoop(Loop *L, LPPassManager &LPM);
     BasicBlock *RewriteLoopExitBlock(Loop *L, BasicBlock *Exit);
     BasicBlock *InsertPreheaderForLoop(Loop *L);
-    Loop *SeparateNestedLoop(Loop *L, LPPassManager &LPM);
+    Loop *SeparateNestedLoop(Loop *L, LPPassManager &LPM,
+                             BasicBlock *Preheader);
     BasicBlock *InsertUniqueBackedgeBlock(Loop *L, BasicBlock *Preheader);
     void PlaceSplitBlockCarefully(BasicBlock *NewBB,
                                   SmallVectorImpl<BasicBlock*> &SplitPreds,
@@ -240,7 +241,7 @@ ReprocessLoop:
     // this for loops with a giant number of backedges, just factor them into a
     // common backedge instead.
     if (L->getNumBackEdges() < 8) {
-      if (SeparateNestedLoop(L, LPM)) {
+      if (SeparateNestedLoop(L, LPM, Preheader)) {
         ++NumNested;
         // This is a big restructuring change, reprocess the whole loop.
         Changed = true;
@@ -379,18 +380,27 @@ BasicBlock *LoopSimplify::InsertPreheaderForLoop(Loop *L) {
   }
 
   // Split out the loop pre-header.
-  BasicBlock *NewBB =
-    SplitBlockPredecessors(Header, OutsideBlocks, ".preheader", this);
+  BasicBlock *PreheaderBB;
+  if (!Header->isLandingPad()) {
+    PreheaderBB = SplitBlockPredecessors(Header, OutsideBlocks, ".preheader",
+                                         this);
+  } else {
+    SmallVector<BasicBlock*, 2> NewBBs;
+    SplitLandingPadPredecessors(Header, OutsideBlocks, ".preheader", 
+                                ".split-lp", this, NewBBs);
+    PreheaderBB = NewBBs[0];
+  }
 
-  NewBB->getTerminator()->setDebugLoc(Header->getFirstNonPHI()->getDebugLoc());
-  DEBUG(dbgs() << "LoopSimplify: Creating pre-header " << NewBB->getName()
-               << "\n");
+  PreheaderBB->getTerminator()->setDebugLoc(
+                                      Header->getFirstNonPHI()->getDebugLoc());
+  DEBUG(dbgs() << "LoopSimplify: Creating pre-header "
+               << PreheaderBB->getName() << "\n");
 
   // Make sure that NewBB is put someplace intelligent, which doesn't mess up
   // code layout too horribly.
-  PlaceSplitBlockCarefully(NewBB, OutsideBlocks, L);
+  PlaceSplitBlockCarefully(PreheaderBB, OutsideBlocks, L);
 
-  return NewBB;
+  return PreheaderBB;
 }
 
 /// RewriteLoopExitBlock - Ensure that the loop preheader dominates all exit
@@ -526,7 +536,17 @@ void LoopSimplify::PlaceSplitBlockCarefully(BasicBlock *NewBB,
 /// If we are able to separate out a loop, return the new outer loop that was
 /// created.
 ///
-Loop *LoopSimplify::SeparateNestedLoop(Loop *L, LPPassManager &LPM) {
+Loop *LoopSimplify::SeparateNestedLoop(Loop *L, LPPassManager &LPM,
+                                       BasicBlock *Preheader) {
+  // Don't try to separate loops without a preheader (this excludes 
+  // loop headers which are targeted by an indirectbr).
+  if (!Preheader)
+    return 0;
+
+  // The header is not a landing pad; preheader insertion should ensure this.
+  assert(!L->getHeader()->isLandingPad() &&
+         "Can't insert backedge to landing pad");
+
   PHINode *PN = FindPHIToPartitionLoops(L, DT, AA, LI);
   if (PN == 0) return 0;  // No known way to partition.
 
@@ -536,13 +556,8 @@ Loop *LoopSimplify::SeparateNestedLoop(Loop *L, LPPassManager &LPM) {
   SmallVector<BasicBlock*, 8> OuterLoopPreds;
   for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
     if (PN->getIncomingValue(i) != PN ||
-        !L->contains(PN->getIncomingBlock(i))) {
-      // We can't split indirectbr edges.
-      if (isa<IndirectBrInst>(PN->getIncomingBlock(i)->getTerminator()))
-        return 0;
-
+        !L->contains(PN->getIncomingBlock(i)))
       OuterLoopPreds.push_back(PN->getIncomingBlock(i));
-    }
 
   DEBUG(dbgs() << "LoopSimplify: Splitting out a new outer loop\n");
 
@@ -636,6 +651,9 @@ LoopSimplify::InsertUniqueBackedgeBlock(Loop *L, BasicBlock *Preheader) {
   if (!Preheader)
     return 0;
 
+  // The header is not a landing pad; preheader insertion should ensure this.
+  assert(!Header->isLandingPad() && "Can't insert backedge to landing pad");
+
   // Figure out which basic blocks contain back-edges to the loop header.
   std::vector<BasicBlock*> BackedgeBlocks;
   for (pred_iterator I = pred_begin(Header), E = pred_end(Header); I != E; ++I){
diff --git a/test/Transforms/LoopSimplify/2011-12-14-LandingpadHeader.ll b/test/Transforms/LoopSimplify/2011-12-14-LandingpadHeader.ll
new file mode 100644
index 00000000000..173a5825767
--- /dev/null
+++ b/test/Transforms/LoopSimplify/2011-12-14-LandingpadHeader.ll
@@ -0,0 +1,45 @@
+; RUN: opt < %s -loop-simplify -S | FileCheck %s
+; PR11575
+
+@catchtypeinfo = external unnamed_addr constant { i8*, i8*, i8* }
+
+define void @main() uwtable ssp {
+entry:
+  invoke void @f1()
+          to label %try.cont19 unwind label %catch
+
+; CHECK: catch.preheader:
+; CHECK-NEXT: landingpad
+; CHECK: br label %catch
+
+; CHECK: catch.split-lp:
+; CHECK-NEXT: landingpad
+; CHECK: br label %catch
+
+catch:                                            ; preds = %if.else, %entry
+  %0 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+          catch i8* bitcast ({ i8*, i8*, i8* }* @catchtypeinfo to i8*)
+  invoke void @f3()
+          to label %if.else unwind label %eh.resume
+
+if.else:                                          ; preds = %catch
+  invoke void @f2()
+          to label %try.cont19 unwind label %catch
+
+try.cont19:                                       ; preds = %if.else, %entry
+  ret void
+
+eh.resume:                                        ; preds = %catch
+  %1 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+          cleanup
+          catch i8* bitcast ({ i8*, i8*, i8* }* @catchtypeinfo to i8*)
+  resume { i8*, i32 } undef
+}
+
+declare i32 @__gxx_personality_v0(...)
+
+declare void @f1()
+
+declare void @f2()
+
+declare void @f3()