From 657105e582ed9d3c95ebe9b721aae1f6def92567 Mon Sep 17 00:00:00 2001
From: Dinesh Dwivedi <dinesh.d@samsung.com>
Date: Tue, 17 Jun 2014 14:34:19 +0000
Subject: [PATCH] Fixed jump threading going to infinite loop.

This patch add code to remove unreachable blocks from function
as they may cause jump threading to stuck in infinite loop.

Differential Revision: http://reviews.llvm.org/D3991

llvm-svn: 211103
---
 llvm/lib/Transforms/Scalar/JumpThreading.cpp  |  3 +++
 .../Transforms/JumpThreading/pr15851_hang.ll  | 22 +++++++++++++++++++
 llvm/test/Transforms/JumpThreading/select.ll  |  2 +-
 3 files changed, 26 insertions(+), 1 deletion(-)
 create mode 100644 llvm/test/Transforms/JumpThreading/pr15851_hang.ll

diff --git a/llvm/lib/Transforms/Scalar/JumpThreading.cpp b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
index 230a381593e0..e501ff29d038 100644
--- a/llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -158,6 +158,9 @@ bool JumpThreading::runOnFunction(Function &F) {
   TLI = &getAnalysis<TargetLibraryInfo>();
   LVI = &getAnalysis<LazyValueInfo>();
 
+  // Remove unreachable blocks from function as they may result in infinite loop.
+  removeUnreachableBlocks(F);
+
   FindLoopHeaders(F);
 
   bool Changed, EverChanged = false;
diff --git a/llvm/test/Transforms/JumpThreading/pr15851_hang.ll b/llvm/test/Transforms/JumpThreading/pr15851_hang.ll
new file mode 100644
index 000000000000..0484bc9f9dc9
--- /dev/null
+++ b/llvm/test/Transforms/JumpThreading/pr15851_hang.ll
@@ -0,0 +1,22 @@
+; RUN: opt -S -jump-threading < %s | FileCheck %s
+
+; CHECK-LABEL: @f(
+; CHECK-LABEL: entry
+; CHECK: ret void
+; CHECK-NOT: for.cond1
+; CHECK-NOT: for.body
+
+define void @f() {
+entry:
+  ret void
+
+for.cond1:
+  %i.025 = phi i32 [ %inc, %for.body ], [ %inc, %for.body ], [ 1, %for.cond1 ]
+  %cmp = icmp slt i32 %i.025, 2
+  br i1 %cmp, label %for.body, label %for.cond1
+
+for.body:
+  %inc = add nsw i32 %i.025, 0
+  %a = icmp ugt i32 %inc, 2
+  br i1 %a, label %for.cond1, label %for.cond1
+}
diff --git a/llvm/test/Transforms/JumpThreading/select.ll b/llvm/test/Transforms/JumpThreading/select.ll
index 201e604e0c5e..545e86c082f4 100644
--- a/llvm/test/Transforms/JumpThreading/select.ll
+++ b/llvm/test/Transforms/JumpThreading/select.ll
@@ -127,7 +127,7 @@ L4:
 ; CHECK: test_switch_default
 ; CHECK: entry:
 ; CHECK: load
-; CHECK: switch
+; CHECK: icmp
 ; CHECK: [[THREADED:[A-Za-z.0-9]+]]:
 ; CHECK: store
 ; CHECK: br