From 0ed57bd81cc9d5c56b4b54474ba39b7d69a69ae1 Mon Sep 17 00:00:00 2001
From: Michael Zolotukhin <mzolotukhin@apple.com>
Date: Tue, 10 Apr 2018 02:16:29 +0000
Subject: [PATCH] [SSAUpdaterBulk] Handle CFG with unreachable from entry
 blocks.

llvm-svn: 329660
---
 lib/Transforms/Utils/SSAUpdaterBulk.cpp       |  2 +-
 .../bb-unreachable-from-entry.ll              | 26 +++++++++++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)
 create mode 100644 test/Transforms/JumpThreading/bb-unreachable-from-entry.ll

diff --git a/lib/Transforms/Utils/SSAUpdaterBulk.cpp b/lib/Transforms/Utils/SSAUpdaterBulk.cpp
index 8f106c57b43..9f358e1d60a 100644
--- a/lib/Transforms/Utils/SSAUpdaterBulk.cpp
+++ b/lib/Transforms/Utils/SSAUpdaterBulk.cpp
@@ -57,7 +57,7 @@ bool SSAUpdaterBulk::HasValueForBlock(unsigned Var, BasicBlock *BB) {
 Value *SSAUpdaterBulk::computeValueAt(BasicBlock *BB, RewriteInfo &R,
                                       DominatorTree *DT) {
   if (!R.Defines.count(BB)) {
-    if (PredCache.get(BB).size()) {
+    if (DT->isReachableFromEntry(BB) && PredCache.get(BB).size()) {
       BasicBlock *IDom = DT->getNode(BB)->getIDom()->getBlock();
       R.Defines[BB] = computeValueAt(IDom, R, DT);
     } else
diff --git a/test/Transforms/JumpThreading/bb-unreachable-from-entry.ll b/test/Transforms/JumpThreading/bb-unreachable-from-entry.ll
new file mode 100644
index 00000000000..5900350f540
--- /dev/null
+++ b/test/Transforms/JumpThreading/bb-unreachable-from-entry.ll
@@ -0,0 +1,26 @@
+; RUN: opt -S < %s -jump-threading | FileCheck %s
+; CHECK-LABEL: @foo
+; CHECK-NEXT: exit2:
+; CHECK-NEXT: ret void
+define void @foo() {
+entry:
+  br label %bb1
+
+entry2:
+  br label %bb1
+
+bb1:
+  %a0 = phi i32 [ undef, %entry2 ], [ 0, %entry ]
+  %b = icmp ne i32 %a0, 0
+  br i1 %b, label %bb2, label %exit2
+
+bb2:
+  br label %exit1
+
+exit1:
+  %a1 = phi i32 [ %a0, %bb2 ]
+  ret void
+
+exit2:
+  ret void
+}