use smallvector instead of vector for a couple worklists.  This speeds up instcombine
by ~10% on some testcases.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@54811 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 74b88b9..9e0a8e7 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -74,7 +74,7 @@
     : public FunctionPass,
       public InstVisitor<InstCombiner, Instruction*> {
     // Worklist of all of the instructions that need to be simplified.
-    std::vector<Instruction*> Worklist;
+    SmallVector<Instruction*, 256> Worklist;
     DenseMap<Instruction*, unsigned> WorklistMap;
     TargetData *TD;
     bool MustPreserveLCSSA;
@@ -11386,7 +11386,7 @@
                                        SmallPtrSet<BasicBlock*, 64> &Visited,
                                        InstCombiner &IC,
                                        const TargetData *TD) {
-  std::vector<BasicBlock*> Worklist;
+  SmallVector<BasicBlock*, 256> Worklist;
   Worklist.push_back(BB);
 
   while (!Worklist.empty()) {