[LVI] Improve LazyValueInfo compile time performance

Changes in LoopUnroll in the past six months exposed scalability
issues in LazyValueInfo when used from JumpThreading. One internal test
that used to take 20s under -O2 now takes 6min.

This commit change the OverDefinedCache from
DenseSet<std::pair<AssertingVH<BasicBlock>, Value*>> to
DenseMap<AssertingVH<BasicBlock>, SmallPtrSet<Value *, 4>>
and reduces compile time down to 1m40s.

Differential Revision: http://reviews.llvm.org/D11651

rdar://problem/21320066

llvm-svn: 245309

1 files changed, 32 insertions, 29 deletions

diff --git a/llvm/lib/Analysis/LazyValueInfo.cpp b/llvm/lib/Analysis/LazyValueInfo.cpp
index f70833b1629..5904257492b 100644
--- a/llvm/lib/Analysis/LazyValueInfo.cpp
+++ b/llvm/lib/Analysis/LazyValueInfo.cpp
@@ -324,8 +324,9 @@ namespace {
     /// This tracks, on a per-block basis, the set of values that are
     /// over-defined at the end of that block.  This is required
     /// for cache updating.
-    typedef std::pair<AssertingVH<BasicBlock>, Value*> OverDefinedPairTy;
-    DenseSet<OverDefinedPairTy> OverDefinedCache;
+    typedef DenseMap<AssertingVH<BasicBlock>, SmallPtrSet<Value *, 4>>
+        OverDefinedCacheTy;
+    OverDefinedCacheTy OverDefinedCache;
 
     /// Keep track of all blocks that we have ever seen, so we
     /// don't spend time removing unused blocks from our caches.
@@ -359,7 +360,7 @@ namespace {
       SeenBlocks.insert(BB);
       lookup(Val)[BB] = Result;
       if (Result.isOverdefined())
-        OverDefinedCache.insert(std::make_pair(BB, Val));
+        OverDefinedCache[BB].insert(Val);
     }
 
     LVILatticeVal getBlockValue(Value *Val, BasicBlock *BB);
@@ -425,14 +426,16 @@ namespace {
 } // end anonymous namespace
 
 void LVIValueHandle::deleted() {
-  typedef std::pair<AssertingVH<BasicBlock>, Value*> OverDefinedPairTy;
-
-  SmallVector<OverDefinedPairTy, 4> ToErase;
-  for (const OverDefinedPairTy &P : Parent->OverDefinedCache)
-    if (P.second == getValPtr())
-      ToErase.push_back(P);
-  for (const OverDefinedPairTy &P : ToErase)
-    Parent->OverDefinedCache.erase(P);
+  SmallVector<AssertingVH<BasicBlock>, 4> ToErase;
+  for (auto &I : Parent->OverDefinedCache) {
+    SmallPtrSetImpl<Value *> &ValueSet = I.second;
+    if (ValueSet.count(getValPtr()))
+      ValueSet.erase(getValPtr());
+    if (ValueSet.empty())
+      ToErase.push_back(I.first);
+  }
+  for (auto &BB : ToErase)
+    Parent->OverDefinedCache.erase(BB);
 
   // This erasure deallocates *this, so it MUST happen after we're done
   // using any and all members of *this.
@@ -446,15 +449,11 @@ void LazyValueInfoCache::eraseBlock(BasicBlock *BB) {
     return;
   SeenBlocks.erase(I);
 
-  SmallVector<OverDefinedPairTy, 4> ToErase;
-  for (const OverDefinedPairTy& P : OverDefinedCache)
-    if (P.first == BB)
-      ToErase.push_back(P);
-  for (const OverDefinedPairTy &P : ToErase)
-    OverDefinedCache.erase(P);
+  auto ODI = OverDefinedCache.find(BB);
+  if (ODI != OverDefinedCache.end())
+    OverDefinedCache.erase(ODI);
 
-  for (std::map<LVIValueHandle, ValueCacheEntryTy>::iterator
-       I = ValueCache.begin(), E = ValueCache.end(); I != E; ++I)
+  for (auto I = ValueCache.begin(), E = ValueCache.end(); I != E; ++I)
     I->second.erase(BB);
 }
 
@@ -483,8 +482,7 @@ bool LazyValueInfoCache::hasBlockValue(Value *Val, BasicBlock *BB) {
     return true;
 
   LVIValueHandle ValHandle(Val, this);
-  std::map<LVIValueHandle, ValueCacheEntryTy>::iterator I =
-    ValueCache.find(ValHandle);
+  auto I = ValueCache.find(ValHandle);
   if (I == ValueCache.end()) return false;
   return I->second.count(BB);
 }
@@ -1053,10 +1051,10 @@ void LazyValueInfoCache::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
   std::vector<BasicBlock*> worklist;
   worklist.push_back(OldSucc);
 
-  DenseSet<Value*> ClearSet;
-  for (OverDefinedPairTy &P : OverDefinedCache)
-    if (P.first == OldSucc)
-      ClearSet.insert(P.second);
+  auto I = OverDefinedCache.find(OldSucc);
+  if (I == OverDefinedCache.end())
+    return; // Nothing to process here.
+  SmallPtrSetImpl<Value *> &ClearSet = I->second;
 
   // Use a worklist to perform a depth-first search of OldSucc's successors.
   // NOTE: We do not need a visited list since any blocks we have already
@@ -1072,9 +1070,12 @@ void LazyValueInfoCache::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
     bool changed = false;
     for (Value *V : ClearSet) {
       // If a value was marked overdefined in OldSucc, and is here too...
-      DenseSet<OverDefinedPairTy>::iterator OI =
-        OverDefinedCache.find(std::make_pair(ToUpdate, V));
-      if (OI == OverDefinedCache.end()) continue;
+      auto OI = OverDefinedCache.find(ToUpdate);
+      if (OI == OverDefinedCache.end())
+        continue;
+      SmallPtrSetImpl<Value *> &ValueSet = OI->second;
+      if (!ValueSet.count(V))
+        continue;
 
       // Remove it from the caches.
       ValueCacheEntryTy &Entry = ValueCache[LVIValueHandle(V, this)];
@@ -1082,7 +1083,9 @@ void LazyValueInfoCache::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
 
       assert(CI != Entry.end() && "Couldn't find entry to update?");
       Entry.erase(CI);
-      OverDefinedCache.erase(OI);
+      ValueSet.erase(V);
+      if (ValueSet.empty())
+        OverDefinedCache.erase(OI);
 
       // If we removed anything, then we potentially need to update
       // blocks successors too.