From 3f4cc3101e4c6cccd2ecc2604205ff819fcfa40f Mon Sep 17 00:00:00 2001
From: Nick Lewycky <nicholas@mxc.ca>
Date: Sun, 9 Mar 2008 07:50:37 +0000
Subject: [PATCH] Firstly, having a BranchInst isn't exclusive with having an
 unwind_to. Secondly, we have to check whether the branch is actually pointing
 to the block with the unwind in it. We could have gotten here because of the
 unwind_to alone.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48099 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Utils/SimplifyCFG.cpp    | 13 ++++++++-----
 test/Transforms/SimplifyCFG/unwindto.ll | 18 ++++++++++++++++++
 2 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index 846c3bf9d9a..b9a9bc1c393 100644
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1364,13 +1364,19 @@ bool llvm::SimplifyCFG(BasicBlock *BB) {
     SmallVector<BasicBlock*, 8> Preds(pred_begin(BB), pred_end(BB));
     while (!Preds.empty()) {
       BasicBlock *Pred = Preds.back();
+
+      if (Pred->getUnwindDest() == BB) {
+        Pred->setUnwindDest(NULL);
+        Changed = true;
+      }
+
       if (BranchInst *BI = dyn_cast<BranchInst>(Pred->getTerminator())) {
-        if (BI->isUnconditional()) {
+        if (BI->isUnconditional() && BI->getSuccessor(0) == BB) {
           Pred->getInstList().pop_back();  // nuke uncond branch
           new UnwindInst(Pred);            // Use unwind.
           Changed = true;
         }
-      } else if (InvokeInst *II = dyn_cast<InvokeInst>(Pred->getTerminator())) {
+      } else if (InvokeInst *II = dyn_cast<InvokeInst>(Pred->getTerminator()))
         if (II->getUnwindDest() == BB) {
           // Insert a new branch instruction before the invoke, because this
           // is now a fall through...
@@ -1388,9 +1394,6 @@ bool llvm::SimplifyCFG(BasicBlock *BB) {
           delete II;
           Changed = true;
         }
-      } else if (Pred->getUnwindDest() == BB) {
-        Pred->setUnwindDest(NULL);
-      }
 
       Preds.pop_back();
     }
diff --git a/test/Transforms/SimplifyCFG/unwindto.ll b/test/Transforms/SimplifyCFG/unwindto.ll
index 28d9d1e6e39..4e91c830150 100644
--- a/test/Transforms/SimplifyCFG/unwindto.ll
+++ b/test/Transforms/SimplifyCFG/unwindto.ll
@@ -41,3 +41,21 @@ entry: unwind_to %cleanup
 cleanup:
   unwind
 }
+
+define i32 @f4() {
+entry: unwind_to %cleanup
+  call void @g(i32 0)
+  br label %cleanup
+cleanup:
+  unwind
+}
+
+define i32 @f5() {
+entry: unwind_to %cleanup
+  call void @g(i32 0)
+  br label %other
+other:
+  ret i32 0
+cleanup:
+  unwind
+}