[VPlan] Replace a few unnecessary includes with forward decls.

llvm/lib/Transforms/Vectorize/LoopVectorizationPlanner.h

@@ -25,18 +25,18 @@
 #define LLVM_TRANSFORMS_VECTORIZE_LOOPVECTORIZATIONPLANNER_H
 
 #include "VPlan.h"
-#include "llvm/Analysis/LoopInfo.h"
-#include "llvm/Analysis/TargetLibraryInfo.h"
-#include "llvm/Analysis/TargetTransformInfo.h"
 
 namespace llvm {
 
+class LoopInfo;
 class LoopVectorizationLegality;
 class LoopVectorizationCostModel;
 class PredicatedScalarEvolution;
 class LoopVectorizationRequirements;
 class LoopVectorizeHints;
 class OptimizationRemarkEmitter;
+class TargetTransformInfo;
+class TargetLibraryInfo;
 class VPRecipeBuilder;
 
 /// VPlan-based builder utility analogous to IRBuilder.

llvm/lib/Transforms/Vectorize/VPlanTransforms.h

@@ -14,11 +14,13 @@
 #define LLVM_TRANSFORMS_VECTORIZE_VPLANTRANSFORMS_H
 
 #include "VPlan.h"
-#include "llvm/IR/Instruction.h"
 #include "llvm/Transforms/Vectorize/LoopVectorizationLegality.h"
 
 namespace llvm {
 
+class Instruction;
+class ScalarEvolution;
+
 struct VPlanTransforms {
   /// Replaces the VPInstructions in \p Plan with corresponding
   /// widen recipes.