From 12f3ca4cdb95b193af905a00e722a4dcb40b3de3 Mon Sep 17 00:00:00 2001
From: Dimitry Andric <dim@FreeBSD.org>
Date: Wed, 26 Apr 2017 19:45:00 +0000
Subject: Vendor import of llvm trunk r301441:
 https://llvm.org/svn/llvm-project/llvm/trunk@301441

---
 lib/Transforms/Utils/LowerSwitch.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

(limited to 'lib/Transforms/Utils/LowerSwitch.cpp')

diff --git a/lib/Transforms/Utils/LowerSwitch.cpp b/lib/Transforms/Utils/LowerSwitch.cpp
index b375d51005d5..8959e77438e9 100644
--- a/lib/Transforms/Utils/LowerSwitch.cpp
+++ b/lib/Transforms/Utils/LowerSwitch.cpp
@@ -403,6 +403,14 @@ void LowerSwitch::processSwitchInst(SwitchInst *SI,
   Value *Val = SI->getCondition();  // The value we are switching on...
   BasicBlock* Default = SI->getDefaultDest();
 
+  // Don't handle unreachable blocks. If there are successors with phis, this
+  // would leave them behind with missing predecessors.
+  if ((CurBlock != &F->getEntryBlock() && pred_empty(CurBlock)) ||
+      CurBlock->getSinglePredecessor() == CurBlock) {
+    DeleteList.insert(CurBlock);
+    return;
+  }
+
   // If there is only the default destination, just branch.
   if (!SI->getNumCases()) {
     BranchInst::Create(Default, CurBlock);
-- 
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