From c7931fd725b390142f9112952b1426560000e6b4 Mon Sep 17 00:00:00 2001
From: Jakob Stoklund Olesen <stoklund@2pi.dk>
Date: Sat, 23 Jul 2011 03:10:17 +0000
Subject: [PATCH] Allow null interference cursors to be queried.

They always report 'no interference'.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135843 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/InterferenceCache.cpp | 5 ++++-
 lib/CodeGen/InterferenceCache.h   | 3 ++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/lib/CodeGen/InterferenceCache.cpp b/lib/CodeGen/InterferenceCache.cpp
index a09bb39f833..29b47bd67ec 100644
--- a/lib/CodeGen/InterferenceCache.cpp
+++ b/lib/CodeGen/InterferenceCache.cpp
@@ -18,10 +18,13 @@
 
 using namespace llvm;
 
+// Static member used for null interference cursors.
+InterferenceCache::BlockInterference InterferenceCache::Cursor::NoInterference;
+
 void InterferenceCache::init(MachineFunction *mf,
                              LiveIntervalUnion *liuarray,
                              SlotIndexes *indexes,
-                            const TargetRegisterInfo *tri) {
+                             const TargetRegisterInfo *tri) {
   MF = mf;
   LIUArray = liuarray;
   TRI = tri;
diff --git a/lib/CodeGen/InterferenceCache.h b/lib/CodeGen/InterferenceCache.h
index 7f0a27a41ba..4df0a9e5c39 100644
--- a/lib/CodeGen/InterferenceCache.h
+++ b/lib/CodeGen/InterferenceCache.h
@@ -138,6 +138,7 @@ public:
   class Cursor {
     Entry *CacheEntry;
     BlockInterference *Current;
+    static BlockInterference NoInterference;
 
     void setEntry(Entry *E) {
       Current = 0;
@@ -175,7 +176,7 @@ public:
 
     /// moveTo - Move cursor to basic block MBBNum.
     void moveToBlock(unsigned MBBNum) {
-      Current = CacheEntry->get(MBBNum);
+      Current = CacheEntry ? CacheEntry->get(MBBNum) : &NoInterference;
     }
 
     /// hasInterference - Return true if the current block has any interference.