fix compile-time regression report by Joerg Sonnenberger:

cache result of Size/OffsetVisitor to speedup analysis of PHI nodes

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172363 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 14 insertions, 10 deletions

diff --git a/include/llvm/Analysis/MemoryBuiltins.h b/include/llvm/Analysis/MemoryBuiltins.h
index f2c564f729..2a9cd75ee7 100644
--- a/include/llvm/Analysis/MemoryBuiltins.h
+++ b/include/llvm/Analysis/MemoryBuiltins.h
@@ -153,12 +153,14 @@ typedef std::pair<APInt, APInt> SizeOffsetType;
 class ObjectSizeOffsetVisitor
   : public InstVisitor<ObjectSizeOffsetVisitor, SizeOffsetType> {
 
+  typedef DenseMap<const Value*, SizeOffsetType> CacheMapTy;
+
   const DataLayout *TD;
   const TargetLibraryInfo *TLI;
   bool RoundToAlign;
   unsigned IntTyBits;
   APInt Zero;
-  SmallPtrSet<Value*, 8> SeenInsts;
+  CacheMapTy CacheMap;
 
   APInt align(APInt Size, uint64_t Align);
 
diff --git a/lib/Analysis/MemoryBuiltins.cpp b/lib/Analysis/MemoryBuiltins.cpp
index f88affb744..1d27a83d93 100644
--- a/lib/Analysis/MemoryBuiltins.cpp
+++ b/lib/Analysis/MemoryBuiltins.cpp
@@ -387,17 +387,19 @@ SizeOffsetType ObjectSizeOffsetVisitor::compute(Value *V) {
   V = V->stripPointerCasts();
 
   if (isa<Instruction>(V) || isa<GEPOperator>(V)) {
-    // If we have already seen this instruction, bail out.
-    if (!SeenInsts.insert(V))
-      return unknown();
-
-    SizeOffsetType Ret;
+    // return cached value or insert unknown in cache if size of V was not
+    // computed yet in order to avoid recursions in PHis
+    std::pair<CacheMapTy::iterator, bool> CacheVal =
+      CacheMap.insert(std::make_pair(V, unknown()));
+    if (!CacheVal.second)
+      return CacheVal.first->second;
+
+    SizeOffsetType Result;
     if (GEPOperator *GEP = dyn_cast<GEPOperator>(V))
-      Ret = visitGEPOperator(*GEP);
+      Result = visitGEPOperator(*GEP);
     else
-      Ret = visit(cast<Instruction>(*V));
-    SeenInsts.erase(V);
-    return Ret;
+      Result = visit(cast<Instruction>(*V));
+    return CacheMap[V] = Result;
   }
 
   if (Argument *A = dyn_cast<Argument>(V))