LIU:::Query: Query LiveRange instead of LiveInterval; NFC

- We only need the information from the base class, not the additional
  details in the LiveInterval class.
- Spread more `const`
- Some code cleanup

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@296684 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/LiveIntervalUnion.h

@@ -57,6 +57,9 @@ public:
   // to reach the current segment's containing virtual register.
   typedef LiveSegments::iterator SegmentIter;
 
+  /// Const version of SegmentIter.
+  typedef LiveSegments::const_iterator ConstSegmentIter;
+
   // LiveIntervalUnions share an external allocator.
   typedef LiveSegments::Allocator Allocator;
 
@@ -72,12 +75,16 @@ public:
   SegmentIter begin() { return Segments.begin(); }
   SegmentIter end() { return Segments.end(); }
   SegmentIter find(SlotIndex x) { return Segments.find(x); }
+  ConstSegmentIter begin() const { return Segments.begin(); }
+  ConstSegmentIter end() const { return Segments.end(); }
+  ConstSegmentIter find(SlotIndex x) const { return Segments.find(x); }
+
   bool empty() const { return Segments.empty(); }
   SlotIndex startIndex() const { return Segments.start(); }
 
   // Provide public access to the underlying map to allow overlap iteration.
   typedef LiveSegments Map;
-  const Map &getMap() { return Segments; }
+  const Map &getMap() const { return Segments; }
 
   /// getTag - Return an opaque tag representing the current state of the union.
   unsigned getTag() const { return Tag; }
@@ -105,45 +112,42 @@ public:
   /// Query interferences between a single live virtual register and a live
   /// interval union.
   class Query {
-    LiveIntervalUnion *LiveUnion = nullptr;
-    LiveInterval *VirtReg = nullptr;
-    LiveInterval::iterator VirtRegI; // current position in VirtReg
-    SegmentIter LiveUnionI;          // current position in LiveUnion
+    const LiveIntervalUnion *LiveUnion = nullptr;
+    const LiveRange *LR = nullptr;
+    LiveRange::const_iterator LRI;  ///< current position in LR
+    ConstSegmentIter LiveUnionI;    ///< current position in LiveUnion
     SmallVector<LiveInterval*,4> InterferingVRegs;
     bool CheckedFirstInterference = false;
     bool SeenAllInterferences = false;
     unsigned Tag = 0;
     unsigned UserTag = 0;
 
-  public:
-    Query() = default;
-    Query(LiveInterval *VReg, LiveIntervalUnion *LIU):
-      LiveUnion(LIU), VirtReg(VReg) {}
-    Query(const Query &) = delete;
-    Query &operator=(const Query &) = delete;
-
-    void clear() {
-      LiveUnion = nullptr;
-      VirtReg = nullptr;
+    void reset(unsigned NewUserTag, const LiveRange &NewLR,
+               const LiveIntervalUnion &NewLiveUnion) {
+      LiveUnion = &NewLiveUnion;
+      LR = &NewLR;
       InterferingVRegs.clear();
       CheckedFirstInterference = false;
       SeenAllInterferences = false;
-      Tag = 0;
-      UserTag = 0;
+      Tag = NewLiveUnion.getTag();
+      UserTag = NewUserTag;
     }
 
-    void init(unsigned UTag, LiveInterval *VReg, LiveIntervalUnion *LIU) {
-      assert(VReg && LIU && "Invalid arguments");
-      if (UserTag == UTag && VirtReg == VReg &&
-          LiveUnion == LIU && !LIU->changedSince(Tag)) {
+  public:
+    Query() = default;
+    Query(const LiveRange &LR, const LiveIntervalUnion &LIU):
+      LiveUnion(&LIU), LR(&LR) {}
+    Query(const Query &) = delete;
+    Query &operator=(const Query &) = delete;
+
+    void init(unsigned NewUserTag, const LiveRange &NewLR,
+              const LiveIntervalUnion &NewLiveUnion) {
+      if (UserTag == NewUserTag && LR == &NewLR && LiveUnion == &NewLiveUnion &&
+          !NewLiveUnion.changedSince(Tag)) {
         // Retain cached results, e.g. firstInterference.
         return;
       }
-      clear();
-      LiveUnion = LIU;
-      VirtReg = VReg;
-      Tag = LIU->getTag();
-      UserTag = UTag;
+      reset(NewUserTag, NewLR, NewLiveUnion);
     }
 
     // Does this live virtual register interfere with the union?

lib/CodeGen/LiveIntervalUnion.cpp

@@ -126,25 +126,24 @@ collectInterferingVRegs(unsigned MaxInterferingRegs) {
     CheckedFirstInterference = true;
 
     // Quickly skip interference check for empty sets.
-    if (VirtReg->empty() || LiveUnion->empty()) {
+    if (LR->empty() || LiveUnion->empty()) {
       SeenAllInterferences = true;
       return 0;
     }
 
-    // In most cases, the union will start before VirtReg.
-    VirtRegI = VirtReg->begin();
+    // In most cases, the union will start before LR.
+    LRI = LR->begin();
     LiveUnionI.setMap(LiveUnion->getMap());
-    LiveUnionI.find(VirtRegI->start);
+    LiveUnionI.find(LRI->start);
   }
 
-  LiveInterval::iterator VirtRegEnd = VirtReg->end();
+  LiveRange::const_iterator LREnd = LR->end();
   LiveInterval *RecentReg = nullptr;
   while (LiveUnionI.valid()) {
-    assert(VirtRegI != VirtRegEnd && "Reached end of VirtReg");
+    assert(LRI != LREnd && "Reached end of LR");
 
     // Check for overlapping interference.
-    while (VirtRegI->start < LiveUnionI.stop() &&
-           VirtRegI->end > LiveUnionI.start()) {
+    while (LRI->start < LiveUnionI.stop() && LRI->end > LiveUnionI.start()) {
       // This is an overlap, record the interfering register.
       LiveInterval *VReg = LiveUnionI.value();
       if (VReg != RecentReg && !isSeenInterference(VReg)) {
@@ -161,20 +160,20 @@ collectInterferingVRegs(unsigned MaxInterferingRegs) {
     }
 
     // The iterators are now not overlapping, LiveUnionI has been advanced
-    // beyond VirtRegI.
-    assert(VirtRegI->end <= LiveUnionI.start() && "Expected non-overlap");
+    // beyond LRI.
+    assert(LRI->end <= LiveUnionI.start() && "Expected non-overlap");
 
     // Advance the iterator that ends first.
-    VirtRegI = VirtReg->advanceTo(VirtRegI, LiveUnionI.start());
-    if (VirtRegI == VirtRegEnd)
+    LRI = LR->advanceTo(LRI, LiveUnionI.start());
+    if (LRI == LREnd)
       break;
 
     // Detect overlap, handle above.
-    if (VirtRegI->start < LiveUnionI.stop())
+    if (LRI->start < LiveUnionI.stop())
       continue;
 
     // Still not overlapping. Catch up LiveUnionI.
-    LiveUnionI.advanceTo(VirtRegI->start);
+    LiveUnionI.advanceTo(LRI->start);
   }
   SeenAllInterferences = true;
   return InterferingVRegs.size();

lib/CodeGen/LiveRegMatrix.cpp

@@ -178,7 +178,7 @@ bool LiveRegMatrix::checkRegUnitInterference(LiveInterval &VirtReg,
 LiveIntervalUnion::Query &LiveRegMatrix::query(LiveInterval &VirtReg,
                                                unsigned RegUnit) {
   LiveIntervalUnion::Query &Q = Queries[RegUnit];
-  Q.init(UserTag, &VirtReg, &Matrix[RegUnit]);
+  Q.init(UserTag, VirtReg, Matrix[RegUnit]);
   return Q;
 }
 

lib/CodeGen/RegAllocGreedy.cpp

@@ -698,7 +698,7 @@ unsigned RAGreedy::canReassign(LiveInterval &VirtReg, unsigned PrevReg) {
     MCRegUnitIterator Units(PhysReg, TRI);
     for (; Units.isValid(); ++Units) {
       // Instantiate a "subquery", not to be confused with the Queries array.
-      LiveIntervalUnion::Query subQ(&VirtReg, &Matrix->getLiveUnions()[*Units]);
+      LiveIntervalUnion::Query subQ(VirtReg, Matrix->getLiveUnions()[*Units]);
       if (subQ.checkInterference())
         break;
     }