Add tags to live interval unions to avoid using stale queries.

The tag is updated whenever the live interval union is changed, and it is tested
before using cached information.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@125224 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/LiveIntervalUnion.cpp b/lib/CodeGen/LiveIntervalUnion.cpp
index 2027db19b75e8b0b195670eb64dfd3b0bbdce577..205f28a0d65a4d0ebe17b9ed2c985352dabef5d5 100644 (file)
--- a/lib/CodeGen/LiveIntervalUnion.cpp
+++ b/lib/CodeGen/LiveIntervalUnion.cpp
@@ -28,6 +28,7 @@ using namespace llvm;
 void LiveIntervalUnion::unify(LiveInterval &VirtReg) {
   if (VirtReg.empty())
     return;
+  ++Tag;
 
   // Insert each of the virtual register's live segments into the map.
   LiveInterval::iterator RegPos = VirtReg.begin();
@@ -46,6 +47,7 @@ void LiveIntervalUnion::unify(LiveInterval &VirtReg) {
 void LiveIntervalUnion::extract(LiveInterval &VirtReg) {
   if (VirtReg.empty())
     return;
+  ++Tag;
 
   // Remove each of the virtual register's live segments from the map.
   LiveInterval::iterator RegPos = VirtReg.begin();

diff --git a/lib/CodeGen/LiveIntervalUnion.h b/lib/CodeGen/LiveIntervalUnion.h
index ff23cf61a3338c16a5d47d5acf54bf1ea569f5d2..6f9c5f4455e9eb5bd62c09c4e7f137304c38fb6e 100644 (file)
--- a/lib/CodeGen/LiveIntervalUnion.h
+++ b/lib/CodeGen/LiveIntervalUnion.h
@@ -64,10 +64,12 @@ public:
 
 private:
   const unsigned RepReg;  // representative register number
+  unsigned Tag;           // unique tag for current contents.
   LiveSegments Segments;  // union of virtual reg segments
 
 public:
-  LiveIntervalUnion(unsigned r, Allocator &a) : RepReg(r), Segments(a) {}
+  LiveIntervalUnion(unsigned r, Allocator &a) : RepReg(r), Tag(0), Segments(a)
+    {}
 
   // Iterate over all segments in the union of live virtual registers ordered
   // by their starting position.
@@ -81,6 +83,12 @@ public:
   typedef LiveSegments Map;
   const Map &getMap() { return Segments; }
 
+  /// getTag - Return an opaque tag representing the current state of the union.
+  unsigned getTag() const { return Tag; }
+
+  /// changedSince - Return true if the union change since getTag returned tag.
+  bool changedSince(unsigned tag) const { return tag != Tag; }
+
   // Add a live virtual register to this union and merge its segments.
   void unify(LiveInterval &VirtReg);
 
@@ -155,6 +163,7 @@ public:
     bool CheckedFirstInterference;
     bool SeenAllInterferences;
     bool SeenUnspillableVReg;
+    unsigned Tag;
 
   public:
     Query(): LiveUnion(), VirtReg() {}
@@ -171,17 +180,19 @@ public:
       CheckedFirstInterference = false;
       SeenAllInterferences = false;
       SeenUnspillableVReg = false;
+      Tag = 0;
     }
 
     void init(LiveInterval *VReg, LiveIntervalUnion *LIU) {
       assert(VReg && LIU && "Invalid arguments");
-      if (VirtReg == VReg && LiveUnion == LIU) {
+      if (VirtReg == VReg && LiveUnion == LIU && !LIU->changedSince(Tag)) {
         // Retain cached results, e.g. firstInterference.
         return;
       }
       clear();
       LiveUnion = LIU;
       VirtReg = VReg;
+      Tag = LIU->getTag();
     }
 
     LiveInterval &virtReg() const {