From a10e89f372220a579faac02a1e4bdb0393b878a7 Mon Sep 17 00:00:00 2001
From: Nick Lewycky <nicholas@mxc.ca>
Date: Mon, 17 Aug 2009 17:00:57 +0000
Subject: [PATCH] Don't crash on critical edge. Patch by Andre Tavares.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@79252 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Utils/SSI.cpp               |  2 +-
 test/Transforms/SSI/2009-08-17-CritEdge.ll | 15 +++++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)
 create mode 100644 test/Transforms/SSI/2009-08-17-CritEdge.ll

diff --git a/lib/Transforms/Utils/SSI.cpp b/lib/Transforms/Utils/SSI.cpp
index 7736f087684..7bb9495f3cf 100644
--- a/lib/Transforms/Utils/SSI.cpp
+++ b/lib/Transforms/Utils/SSI.cpp
@@ -95,7 +95,7 @@ void SSI::insertSigmaFunctions(SmallVectorImpl<Instruction *> &value) {
           // Next Basic Block
           BasicBlock *BB_next = TI->getSuccessor(j);
           if (BB_next != BB &&
-              BB_next->getUniquePredecessor() != NULL &&
+              BB_next->getSinglePredecessor() != NULL &&
               dominateAny(BB_next, value[i])) {
             PHINode *PN = PHINode::Create(
                 value[i]->getType(), SSI_SIG, BB_next->begin());
diff --git a/test/Transforms/SSI/2009-08-17-CritEdge.ll b/test/Transforms/SSI/2009-08-17-CritEdge.ll
new file mode 100644
index 00000000000..e5d1183dab0
--- /dev/null
+++ b/test/Transforms/SSI/2009-08-17-CritEdge.ll
@@ -0,0 +1,15 @@
+; RUN: llvm-as < %s | opt -abcd -disable-output
+
+define void @test(i32 %x) {
+entry:
+  br label %label1
+label1:
+  %A = phi i32 [ 0, %entry ], [ %A.1, %label2 ]
+  %B = icmp slt i32 %A, %x
+  br i1 %B, label %label2, label %label2
+label2:
+  %A.1 = add i32 %A, 1
+  br label %label1
+label3:  ; No predecessors!
+  ret void
+}