Allow null interference cursors to be queried.

They always report 'no interference'.

llvm-svn: 135843

2 files changed, 6 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/InterferenceCache.cpp b/llvm/lib/CodeGen/InterferenceCache.cpp
index a09bb39f833..29b47bd67ec 100644
--- a/llvm/lib/CodeGen/InterferenceCache.cpp
+++ b/llvm/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/llvm/lib/CodeGen/InterferenceCache.h b/llvm/lib/CodeGen/InterferenceCache.h
index 7f0a27a41ba..4df0a9e5c39 100644
--- a/llvm/lib/CodeGen/InterferenceCache.h
+++ b/llvm/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.