Revert "Repace SmallPtrSet with SmallPtrSetImpl in function arguments to avoid needing to mention the size."

Getting a weird buildbot failure that I need to investigate.

llvm-svn: 215870
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 5716e24..4edfb61 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -1833,7 +1833,7 @@
 
 /// GetStringLengthH - If we can compute the length of the string pointed to by
 /// the specified pointer, return 'len+1'.  If we can't, return 0.
-static uint64_t GetStringLengthH(Value *V, SmallPtrSetImpl<PHINode*> &PHIs) {
+static uint64_t GetStringLengthH(Value *V, SmallPtrSet<PHINode*, 32> &PHIs) {
   // Look through noop bitcast instructions.
   V = V->stripPointerCasts();