[llvm] r290759 - [LVI] Manually hoist computation from loop

[Philip Reames via llvm-commits]

Author: reames
Date: Fri Dec 30 11:56:47 2016
New Revision: 290759

URL: http://llvm.org/viewvc/llvm-project?rev=290759&view=rev
Log:
[LVI] Manually hoist computation from loop

Minor compile time win.  Not known to be a hot spot, just something I noticed while reading.


Modified:
    llvm/trunk/lib/Analysis/LazyValueInfo.cpp

Modified: llvm/trunk/lib/Analysis/LazyValueInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/LazyValueInfo.cpp?rev=290759&r1=290758&r2=290759&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/LazyValueInfo.cpp (original)
+++ llvm/trunk/lib/Analysis/LazyValueInfo.cpp Fri Dec 30 11:56:47 2016
@@ -525,23 +525,28 @@ void LazyValueInfoCache::threadEdgeImpl(
     // Skip blocks only accessible through NewSucc.
     if (ToUpdate == NewSucc) continue;
 
+    // If a value was marked overdefined in OldSucc, and is here too...
+    auto OI = OverDefinedCache.find(ToUpdate);
+    if (OI == OverDefinedCache.end())
+      continue;
+    SmallPtrSetImpl<Value *> &ValueSet = OI->second;
+
     bool changed = false;
     for (Value *V : ValsToClear) {
-      // If a value was marked overdefined in OldSucc, and is here too...
-      auto OI = OverDefinedCache.find(ToUpdate);
-      if (OI == OverDefinedCache.end())
-        continue;
-      SmallPtrSetImpl<Value *> &ValueSet = OI->second;
+      // TODO: count and erase can be converted to a find/erase(itr) pattern
       if (!ValueSet.count(V))
         continue;
 
       ValueSet.erase(V);
-      if (ValueSet.empty())
-        OverDefinedCache.erase(OI);
 
       // If we removed anything, then we potentially need to update
       // blocks successors too.
       changed = true;
+
+      if (ValueSet.empty()) {
+        OverDefinedCache.erase(OI);
+        break;
+      }
     }
 
     if (!changed) continue;