From 2c7ed11d93239dacf81540e2307f0db456bb9122 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Mon, 19 Jan 2009 21:20:34 +0000
Subject: [PATCH] Fix PR3353, infinitely jump threading an infinite loop make
 from switches.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@62529 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/JumpThreading.cpp       |  5 +++++
 .../JumpThreading/2009-01-19-InfSwitchLoop.ll | 21 +++++++++++++++++++
 2 files changed, 26 insertions(+)
 create mode 100644 test/Transforms/JumpThreading/2009-01-19-InfSwitchLoop.ll

diff --git a/lib/Transforms/Scalar/JumpThreading.cpp b/lib/Transforms/Scalar/JumpThreading.cpp
index 94d33aa7879..f96fc208ae1 100644
--- a/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/lib/Transforms/Scalar/JumpThreading.cpp
@@ -419,6 +419,11 @@ bool JumpThreading::ProcessBranchOnDuplicateCond(BasicBlock *PredBB,
 /// switches out of repeated 'if' conditions.
 bool JumpThreading::ProcessSwitchOnDuplicateCond(BasicBlock *PredBB,
                                                  BasicBlock *DestBB) {
+  // Can't thread edge to self.
+  if (PredBB == DestBB)
+    return false;
+  
+  
   SwitchInst *PredSI = cast<SwitchInst>(PredBB->getTerminator());
   SwitchInst *DestSI = cast<SwitchInst>(DestBB->getTerminator());
 
diff --git a/test/Transforms/JumpThreading/2009-01-19-InfSwitchLoop.ll b/test/Transforms/JumpThreading/2009-01-19-InfSwitchLoop.ll
new file mode 100644
index 00000000000..ab8b087f8a4
--- /dev/null
+++ b/test/Transforms/JumpThreading/2009-01-19-InfSwitchLoop.ll
@@ -0,0 +1,21 @@
+; RUN: llvm-as < %s | opt -jump-threading | llvm-dis
+; PR3353
+
+define i32 @test(i8 %X) {
+entry:
+	%Y = add i8 %X, 1
+	%Z = add i8 %Y, 1
+	br label %bb33.i
+
+bb33.i:		; preds = %bb33.i, %bb32.i
+	switch i8 %Y, label %bb32.i [
+		i8 39, label %bb35.split.i
+		i8 13, label %bb33.i
+	]
+
+bb35.split.i:
+	ret i32 5
+bb32.i:
+	ret i32 1
+}
+