From f7b5d2de13fce734724d9e062fe2307e3449c8ea Mon Sep 17 00:00:00 2001
From: Slava Pestov <spestov@apple.com>
Date: Wed, 21 Sep 2016 20:05:23 -0700
Subject: [PATCH] SIL Optimizer: Fix bug in EscapeAnalysis::isReachable()

We weren't clearing the worklist flags if returning true here. Oops!

This would manifest as alias analysis returning different results
for the same operands over time, which confused ARC code motion
into dropping release instructions.
---
 lib/SILOptimizer/Analysis/EscapeAnalysis.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/SILOptimizer/Analysis/EscapeAnalysis.cpp b/lib/SILOptimizer/Analysis/EscapeAnalysis.cpp
index 89f47ac688cf4..a505fdc39ba32 100644
--- a/lib/SILOptimizer/Analysis/EscapeAnalysis.cpp
+++ b/lib/SILOptimizer/Analysis/EscapeAnalysis.cpp
@@ -560,8 +560,10 @@ bool EscapeAnalysis::ConnectionGraph::isReachable(CGNode *From, CGNode *To) {
   From->isInWorkList = true;
   for (unsigned Idx = 0; Idx < WorkList.size(); ++Idx) {
     CGNode *Reachable = WorkList[Idx];
-    if (Reachable == To)
+    if (Reachable == To) {
+      clearWorkListFlags(WorkList);
       return true;
+    }
     for (Predecessor Pred : Reachable->Preds) {
       CGNode *PredNode = Pred.getPointer();
       if (!PredNode->isInWorkList) {