Avoid overly large SmallPtrSet/SmallSet

These sets perform linear searching in small mode so it is never a good
idea to use SmallSize/N bigger than 32.

llvm-svn: 259283
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 329a1f1..e713f90 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -3001,7 +3001,7 @@
   // Do a depth-first traversal of the function, populate the worklist with
   // the reachable instructions.  Ignore blocks that are not reachable.  Keep
   // track of which blocks we visit.
-  SmallPtrSet<BasicBlock *, 64> Visited;
+  SmallPtrSet<BasicBlock *, 32> Visited;
   MadeIRChange |=
       AddReachableCodeToWorklist(&F.front(), DL, Visited, ICWorklist, TLI);