[LazyValueInfo] Stop inserting overdefined values into ValueCache to

reduce memory usage.

Previously, LazyValueInfoCache inserted overdefined lattice values into
both ValueCache and OverDefinedCache. This wasn't necessary and was
causing LazyValueInfo to use an excessive amount of memory in some cases.

This patch changes LazyValueInfoCache to insert overdefined values only
into OverDefinedCache. The memory usage decreases by 70 to 75% when one
of the files in llvm is compiled.

rdar://problem/11388615

Differential revision: http://reviews.llvm.org/D15391

llvm-svn: 255320

llvm/lib/Analysis/LazyValueInfo.cpp

@@ -105,6 +105,11 @@ public:
     Res.markConstantRange(CR);
     return Res;
   }
+  static LVILatticeVal getOverdefined() {
+    LVILatticeVal Res;
+    Res.markOverdefined();
+    return Res;
+  }
   
   bool isUndefined() const     { return Tag == undefined; }
   bool isConstant() const      { return Tag == constant; }
@@ -316,6 +321,8 @@ namespace {
     /// This is all of the cached block information for exactly one Value*.
     /// The entries are sorted by the BasicBlock* of the
     /// entries, allowing us to do a lookup with a binary search.
+    /// Over-defined lattice values are recorded in OverDefinedCache to reduce
+    /// memory overhead.
     typedef SmallDenseMap<AssertingVH<BasicBlock>, LVILatticeVal, 4>
         ValueCacheEntryTy;
 
@@ -324,8 +331,7 @@ namespace {
     std::map<LVIValueHandle, ValueCacheEntryTy> ValueCache;
 
     /// This tracks, on a per-block basis, the set of values that are
-    /// over-defined at the end of that block.  This is required
+    /// over-defined at the end of that block.
-    /// for cache updating.
     typedef DenseMap<AssertingVH<BasicBlock>, SmallPtrSet<Value *, 4>>
         OverDefinedCacheTy;
     OverDefinedCacheTy OverDefinedCache;
@@ -360,9 +366,13 @@ namespace {
 
     void insertResult(Value *Val, BasicBlock *BB, const LVILatticeVal &Result) {
       SeenBlocks.insert(BB);
-      lookup(Val)[BB] = Result;
+
+      // Insert over-defined values into their own cache to reduce memory
+      // overhead.
       if (Result.isOverdefined())
         OverDefinedCache[BB].insert(Val);
+      else
+        lookup(Val)[BB] = Result;
     }
 
     LVILatticeVal getBlockValue(Value *Val, BasicBlock *BB);
@@ -390,6 +400,34 @@ namespace {
       return ValueCache[LVIValueHandle(V, this)];
     }
 
+    bool isOverdefined(Value *V, BasicBlock *BB) const {
+      auto ODI = OverDefinedCache.find(BB);
+
+      if (ODI == OverDefinedCache.end())
+        return false;
+
+      return ODI->second.count(V);
+    }
+
+    bool hasCachedValueInfo(Value *V, BasicBlock *BB) {
+      if (isOverdefined(V, BB))
+        return true;
+
+      LVIValueHandle ValHandle(V, this);
+      auto I = ValueCache.find(ValHandle);
+      if (I == ValueCache.end())
+        return false;
+
+      return I->second.count(BB);
+    }
+
+    LVILatticeVal getCachedValueInfo(Value *V, BasicBlock *BB) {
+      if (isOverdefined(V, BB))
+        return LVILatticeVal::getOverdefined();
+
+      return lookup(V)[BB];
+    }
+    
   public:
     /// This is the query interface to determine the lattice
     /// value for the specified Value* at the end of the specified block.
@@ -467,7 +505,8 @@ void LazyValueInfoCache::solve() {
     if (solveBlockValue(e.second, e.first)) {
       // The work item was completely processed.
       assert(BlockValueStack.top() == e && "Nothing should have been pushed!");
-      assert(lookup(e.second).count(e.first) && "Result should be in cache!");
+      assert(hasCachedValueInfo(e.second, e.first) &&
+             "Result should be in cache!");
 
       BlockValueStack.pop();
       BlockValueSet.erase(e);
@@ -483,10 +522,7 @@ bool LazyValueInfoCache::hasBlockValue(Value *Val, BasicBlock *BB) {
   if (isa<Constant>(Val))
     return true;
 
-  LVIValueHandle ValHandle(Val, this);
+  return hasCachedValueInfo(Val, BB);
-  auto I = ValueCache.find(ValHandle);
-  if (I == ValueCache.end()) return false;
-  return I->second.count(BB);
 }
 
 LVILatticeVal LazyValueInfoCache::getBlockValue(Value *Val, BasicBlock *BB) {
@@ -495,7 +531,7 @@ LVILatticeVal LazyValueInfoCache::getBlockValue(Value *Val, BasicBlock *BB) {
     return LVILatticeVal::get(VC);
 
   SeenBlocks.insert(BB);
-  return lookup(Val)[BB];
+  return getCachedValueInfo(Val, BB);
 }
 
 static LVILatticeVal getFromRangeMetadata(Instruction *BBI) {
@@ -521,10 +557,10 @@ bool LazyValueInfoCache::solveBlockValue(Value *Val, BasicBlock *BB) {
   if (isa<Constant>(Val))
     return true;
 
-  if (lookup(Val).count(BB)) {
+  if (hasCachedValueInfo(Val, BB)) {
     // If we have a cached value, use that.
     DEBUG(dbgs() << "  reuse BB '" << BB->getName()
-                 << "' val=" << lookup(Val)[BB] << '\n');
+                 << "' val=" << getCachedValueInfo(Val, BB) << '\n');
 
     // Since we're reusing a cached value, we don't need to update the
     // OverDefinedCache. The cache will have been properly updated whenever the
@@ -1106,12 +1142,6 @@ void LazyValueInfoCache::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
       if (!ValueSet.count(V))
         continue;
 
-      // Remove it from the caches.
-      ValueCacheEntryTy &Entry = ValueCache[LVIValueHandle(V, this)];
-      ValueCacheEntryTy::iterator CI = Entry.find(ToUpdate);
-
-      assert(CI != Entry.end() && "Couldn't find entry to update?");
-      Entry.erase(CI);
       ValueSet.erase(V);
       if (ValueSet.empty())
         OverDefinedCache.erase(OI);