2 files changed, 98 insertions, 0 deletions

diff --git a/lib/Transforms/Scalar/CodeGenPrepare.cpp b/lib/Transforms/Scalar/CodeGenPrepare.cpp
index 61adb2dc12..c4df154529 100644
--- a/lib/Transforms/Scalar/CodeGenPrepare.cpp
+++ b/lib/Transforms/Scalar/CodeGenPrepare.cpp
@@ -22,6 +22,7 @@
 #include "llvm/InlineAsm.h"
 #include "llvm/Instructions.h"
 #include "llvm/IntrinsicInst.h"
+#include "llvm/Module.h"
 #include "llvm/Pass.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/SmallSet.h"
@@ -183,8 +184,12 @@ bool CodeGenPrepare::runOnFunction(Function &F) {
   if (!DisableBranchOpts) {
     MadeChange = false;
     SmallPtrSet<BasicBlock*, 8> WorkList;
+    SmallPtrSet<BasicBlock*, 8> LPadList;
+    SmallVector<BasicBlock*, 8> ReturnList;
     for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
       SmallVector<BasicBlock*, 2> Successors(succ_begin(BB), succ_end(BB));
+      if (BB->isLandingPad()) LPadList.insert(BB);
+      if (isa<ReturnInst>(BB->getTerminator())) ReturnList.push_back(BB);
       MadeChange |= ConstantFoldTerminator(BB, true);
       if (!MadeChange) continue;
 
@@ -195,9 +200,11 @@ bool CodeGenPrepare::runOnFunction(Function &F) {
     }
 
     // Delete the dead blocks and any of their dead successors.
+    bool HadLPads = !LPadList.empty();
     while (!WorkList.empty()) {
       BasicBlock *BB = *WorkList.begin();
       WorkList.erase(BB);
+      LPadList.erase(BB);
       SmallVector<BasicBlock*, 2> Successors(succ_begin(BB), succ_end(BB));
 
       DeleteDeadBlock(BB);
@@ -208,6 +215,74 @@ bool CodeGenPrepare::runOnFunction(Function &F) {
           WorkList.insert(*II);
     }
 
+    if (HadLPads && LPadList.empty()) {
+      // All of the landing pads were removed. Get rid of the SjLj EH context
+      // code.
+      Module *M = F.getParent();
+
+      // These functions must exist if we have SjLj EH code to clean up.
+      Constant *RegisterFn = M->getFunction("_Unwind_SjLj_Register");
+      Constant *UnregisterFn = M->getFunction("_Unwind_SjLj_Unregister");
+
+      if (RegisterFn) {
+        Constant *LSDAAddrFn =
+          Intrinsic::getDeclaration(M, Intrinsic::eh_sjlj_lsda);
+        Constant *FrameAddrFn =
+          Intrinsic::getDeclaration(M, Intrinsic::frameaddress);
+        Constant *StackAddrFn =
+          Intrinsic::getDeclaration(M, Intrinsic::stacksave);
+        Constant *BuiltinSetjmpFn =
+          Intrinsic::getDeclaration(M, Intrinsic::eh_sjlj_setjmp);
+        Constant *FuncCtxFn =
+          Intrinsic::getDeclaration(M, Intrinsic::eh_sjlj_functioncontext);
+
+        BasicBlock &Entry = F.getEntryBlock();
+        SmallVector<Instruction*, 8> DeadInsts;
+        for (BasicBlock::iterator I = Entry.begin(), E = Entry.end();
+             I != E; ++I) {
+          if (CallInst *CI = dyn_cast<CallInst>(I)) {
+            Value *Callee = CI->getCalledValue();
+            bool IsDead = true;
+            if (Callee != LSDAAddrFn && Callee != FrameAddrFn &&
+                Callee != StackAddrFn && Callee != BuiltinSetjmpFn &&
+                Callee != FuncCtxFn && Callee != RegisterFn)
+              IsDead = false;
+
+            if (IsDead) {
+              Type *Ty = CI->getType();
+              if (!Ty->isVoidTy())
+                CI->replaceAllUsesWith(UndefValue::get(Ty));
+              DeadInsts.push_back(CI);
+            }
+          }
+        }
+
+        // Find and remove the unregister calls.
+        for (SmallVectorImpl<BasicBlock*>::iterator I = ReturnList.begin(),
+               E = ReturnList.end(); I != E; ++I) {
+          BasicBlock *BB = *I;
+          typedef BasicBlock::InstListType::reverse_iterator reverse_iterator;
+
+          for (reverse_iterator II = BB->getInstList().rbegin(),
+                 IE = BB->getInstList().rend(); II != IE; ++II) {
+            if (CallInst *CI = dyn_cast<CallInst>(&*II)) {
+              Value *Callee = CI->getCalledValue();
+
+              if (Callee == UnregisterFn) {
+                DeadInsts.push_back(CI);
+                break;
+              }
+            }
+          }
+        }
+
+        // Kill the dead instructions.
+        for (SmallVectorImpl<Instruction*>::iterator I = DeadInsts.begin(),
+               E = DeadInsts.end(); I != E; ++I)
+          (*I)->eraseFromParent();
+      }
+    }
+
     // Merge pairs of basic blocks with unconditional branches, connected by
     // a single edge.
     if (EverMadeChange || MadeChange)
diff --git a/test/CodeGen/ARM/crash.ll b/test/CodeGen/ARM/crash.ll
index 0f6f33e044..4e3e2010b0 100644
--- a/test/CodeGen/ARM/crash.ll
+++ b/test/CodeGen/ARM/crash.ll
@@ -69,3 +69,26 @@ bb:
   store <4 x float> %tmp154, <4 x float>* undef, align 16
   ret void
 }
+
+; <rdar://problem/12721258>
+%A = type { %B }
+%B = type { i32 }
+
+define void @_Z3Foov() ssp {
+entry:
+  br i1 true, label %exit, label %false
+
+false:
+  invoke void undef(%A* undef)
+          to label %exit unwind label %lpad
+
+lpad:
+  %0 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_sj0 to i8*)
+          catch i8* null
+  unreachable
+
+exit:
+  ret void
+}
+
+declare i32 @__gxx_personality_sj0(...)