diff --git a/llvm/include/llvm/Transforms/IPO/Attributor.h b/llvm/include/llvm/Transforms/IPO/Attributor.h
index 884f8191368cb9..1a9dde03aabc61 100644
--- a/llvm/include/llvm/Transforms/IPO/Attributor.h
+++ b/llvm/include/llvm/Transforms/IPO/Attributor.h
@@ -133,7 +133,6 @@ struct InformationCache;
 struct AAIsDead;
 struct AttributorCallGraph;
 
-class AAManager;
 class AAResults;
 class Function;
 
diff --git a/llvm/include/llvm/Transforms/IPO/ModuleInliner.h b/llvm/include/llvm/Transforms/IPO/ModuleInliner.h
index 963d74d7100389..7474e48aafaf38 100644
--- a/llvm/include/llvm/Transforms/IPO/ModuleInliner.h
+++ b/llvm/include/llvm/Transforms/IPO/ModuleInliner.h
@@ -18,9 +18,6 @@
 
 namespace llvm {
 
-class AssumptionCacheTracker;
-class ProfileSummaryInfo;
-
 /// The module inliner pass for the new pass manager.
 ///
 /// This pass wires together the inlining utilities and the inline cost
diff --git a/llvm/include/llvm/Transforms/IPO/PassManagerBuilder.h b/llvm/include/llvm/Transforms/IPO/PassManagerBuilder.h
index 7f321a688aff0c..3b944878a81025 100644
--- a/llvm/include/llvm/Transforms/IPO/PassManagerBuilder.h
+++ b/llvm/include/llvm/Transforms/IPO/PassManagerBuilder.h
@@ -24,7 +24,6 @@ namespace llvm {
 class ModuleSummaryIndex;
 class Pass;
 class TargetLibraryInfoImpl;
-class TargetMachine;
 
 // The old pass manager infrastructure is hidden in a legacy namespace now.
 namespace legacy {
diff --git a/llvm/include/llvm/Transforms/Scalar/GVN.h b/llvm/include/llvm/Transforms/Scalar/GVN.h
index cbe5057b9cde44..9e660c92124efc 100644
--- a/llvm/include/llvm/Transforms/Scalar/GVN.h
+++ b/llvm/include/llvm/Transforms/Scalar/GVN.h
@@ -39,11 +39,9 @@ class AssumptionCache;
 class BasicBlock;
 class BranchInst;
 class CallInst;
-class Constant;
 class ExtractValueInst;
 class Function;
 class FunctionPass;
-class IntrinsicInst;
 class LoadInst;
 class LoopInfo;
 class MemDepResult;
diff --git a/llvm/include/llvm/Transforms/Scalar/InstSimplifyPass.h b/llvm/include/llvm/Transforms/Scalar/InstSimplifyPass.h
index f5781e085f7bf8..09a4a95401d84c 100644
--- a/llvm/include/llvm/Transforms/Scalar/InstSimplifyPass.h
+++ b/llvm/include/llvm/Transforms/Scalar/InstSimplifyPass.h
@@ -18,8 +18,6 @@
 
 namespace llvm {
 
-class FunctionPass;
-
 /// Run instruction simplification across each instruction in the function.
 ///
 /// Instruction simplification has useful constraints in some contexts:
diff --git a/llvm/include/llvm/Transforms/Scalar/LoopReroll.h b/llvm/include/llvm/Transforms/Scalar/LoopReroll.h
index 6ae309e48a281d..496e8df85ea05d 100644
--- a/llvm/include/llvm/Transforms/Scalar/LoopReroll.h
+++ b/llvm/include/llvm/Transforms/Scalar/LoopReroll.h
@@ -14,8 +14,6 @@
 
 namespace llvm {
 
-class Function;
-
 class LoopRerollPass : public PassInfoMixin<LoopRerollPass> {
 public:
   PreservedAnalyses run(Loop &L, LoopAnalysisManager &AM,
diff --git a/llvm/include/llvm/Transforms/Scalar/LoopUnrollAndJamPass.h b/llvm/include/llvm/Transforms/Scalar/LoopUnrollAndJamPass.h
index 6125fc7636a066..72663d3d62a88c 100644
--- a/llvm/include/llvm/Transforms/Scalar/LoopUnrollAndJamPass.h
+++ b/llvm/include/llvm/Transforms/Scalar/LoopUnrollAndJamPass.h
@@ -13,7 +13,6 @@
 #include "llvm/Transforms/Scalar/LoopPassManager.h"
 
 namespace llvm {
-class Function;
 
 /// A simple loop rotation transformation.
 class LoopUnrollAndJamPass : public PassInfoMixin<LoopUnrollAndJamPass> {
diff --git a/llvm/include/llvm/Transforms/Scalar/SCCP.h b/llvm/include/llvm/Transforms/Scalar/SCCP.h
index 2d7c94918699c7..cd410044788032 100644
--- a/llvm/include/llvm/Transforms/Scalar/SCCP.h
+++ b/llvm/include/llvm/Transforms/Scalar/SCCP.h
@@ -32,8 +32,6 @@
 
 namespace llvm {
 
-class PostDominatorTree;
-
 /// This pass performs function-level constant propagation and merging.
 class SCCPPass : public PassInfoMixin<SCCPPass> {
 public:
diff --git a/llvm/include/llvm/Transforms/Scalar/SROA.h b/llvm/include/llvm/Transforms/Scalar/SROA.h
index f1a43435d89a35..b74c45e71d9557 100644
--- a/llvm/include/llvm/Transforms/Scalar/SROA.h
+++ b/llvm/include/llvm/Transforms/Scalar/SROA.h
@@ -27,7 +27,6 @@ class AllocaInst;
 class AssumptionCache;
 class DominatorTree;
 class Function;
-class Instruction;
 class LLVMContext;
 class PHINode;
 class SelectInst;
diff --git a/llvm/include/llvm/Transforms/Scalar/WarnMissedTransforms.h b/llvm/include/llvm/Transforms/Scalar/WarnMissedTransforms.h
index 2d5942a3f56901..04a5f7e6ff38c1 100644
--- a/llvm/include/llvm/Transforms/Scalar/WarnMissedTransforms.h
+++ b/llvm/include/llvm/Transforms/Scalar/WarnMissedTransforms.h
@@ -17,8 +17,6 @@
 
 namespace llvm {
 class Function;
-class Loop;
-class LPMUpdater;
 
 // New pass manager boilerplate.
 class WarnMissedTransformationsPass
diff --git a/llvm/include/llvm/Transforms/Utils/AssumeBundleBuilder.h b/llvm/include/llvm/Transforms/Utils/AssumeBundleBuilder.h
index 5c06af9bc84ca6..a497722eece629 100644
--- a/llvm/include/llvm/Transforms/Utils/AssumeBundleBuilder.h
+++ b/llvm/include/llvm/Transforms/Utils/AssumeBundleBuilder.h
@@ -22,7 +22,6 @@
 #include "llvm/IR/PassManager.h"
 
 namespace llvm {
-class IntrinsicInst;
 class AssumptionCache;
 class DominatorTree;
 
diff --git a/llvm/include/llvm/Transforms/Utils/Cloning.h b/llvm/include/llvm/Transforms/Utils/Cloning.h
index 5a1f322b20544c..fdc55bea99e7bf 100644
--- a/llvm/include/llvm/Transforms/Utils/Cloning.h
+++ b/llvm/include/llvm/Transforms/Utils/Cloning.h
@@ -33,13 +33,11 @@ class AAResults;
 class AllocaInst;
 class BasicBlock;
 class BlockFrequencyInfo;
-class CallInst;
 class CallGraph;
 class DebugInfoFinder;
 class DominatorTree;
 class Function;
 class Instruction;
-class InvokeInst;
 class Loop;
 class LoopInfo;
 class Module;
diff --git a/llvm/include/llvm/Transforms/Utils/CodeLayout.h b/llvm/include/llvm/Transforms/Utils/CodeLayout.h
index 987a5651a8b63e..a0e5f8c7d014c1 100644
--- a/llvm/include/llvm/Transforms/Utils/CodeLayout.h
+++ b/llvm/include/llvm/Transforms/Utils/CodeLayout.h
@@ -20,8 +20,6 @@
 
 namespace llvm {
 
-class MachineBasicBlock;
-
 /// Find a layout of nodes (basic blocks) of a given CFG optimizing jump
 /// locality and thus processor I-cache utilization. This is achieved via
 /// increasing the number of fall-through jumps and co-locating frequently
diff --git a/llvm/include/llvm/Transforms/Utils/CtorUtils.h b/llvm/include/llvm/Transforms/Utils/CtorUtils.h
index 3625ee662b1ce0..3ef3ba244b4386 100644
--- a/llvm/include/llvm/Transforms/Utils/CtorUtils.h
+++ b/llvm/include/llvm/Transforms/Utils/CtorUtils.h
@@ -17,7 +17,6 @@
 
 namespace llvm {
 
-class GlobalVariable;
 class Function;
 class Module;
 
diff --git a/llvm/include/llvm/Transforms/Utils/Local.h b/llvm/include/llvm/Transforms/Utils/Local.h
index a914c6e0925f2e..8a6f172b78d498 100644
--- a/llvm/include/llvm/Transforms/Utils/Local.h
+++ b/llvm/include/llvm/Transforms/Utils/Local.h
@@ -42,9 +42,7 @@ class BasicBlock;
 class BranchInst;
 class CallBase;
 class CallInst;
-class DbgDeclareInst;
 class DbgVariableIntrinsic;
-class DbgValueInst;
 class DIBuilder;
 class DomTreeUpdater;
 class Function;
diff --git a/llvm/include/llvm/Transforms/Utils/LoopUtils.h b/llvm/include/llvm/Transforms/Utils/LoopUtils.h
index e0a9115f61b05a..3a712d78df6711 100644
--- a/llvm/include/llvm/Transforms/Utils/LoopUtils.h
+++ b/llvm/include/llvm/Transforms/Utils/LoopUtils.h
@@ -37,7 +37,6 @@ class MemorySSAUpdater;
 class OptimizationRemarkEmitter;
 class PredIteratorCache;
 class ScalarEvolution;
-class ScalarEvolutionExpander;
 class SCEV;
 class SCEVExpander;
 class TargetLibraryInfo;
diff --git a/llvm/include/llvm/Transforms/Utils/MemoryOpRemark.h b/llvm/include/llvm/Transforms/Utils/MemoryOpRemark.h
index e5f8a46eaf234a..8dc0f1e26a9288 100644
--- a/llvm/include/llvm/Transforms/Utils/MemoryOpRemark.h
+++ b/llvm/include/llvm/Transforms/Utils/MemoryOpRemark.h
@@ -27,8 +27,6 @@ class Instruction;
 class IntrinsicInst;
 class Value;
 class OptimizationRemarkEmitter;
-class OptimizationRemarkMissed;
-class OptimizationRemarkAnalysis;
 class StoreInst;
 
 // FIXME: Once we get to more remarks like this one, we need to re-evaluate how
diff --git a/llvm/include/llvm/Transforms/Utils/UnifyFunctionExitNodes.h b/llvm/include/llvm/Transforms/Utils/UnifyFunctionExitNodes.h
index 20b36021250638..461669d6a21787 100644
--- a/llvm/include/llvm/Transforms/Utils/UnifyFunctionExitNodes.h
+++ b/llvm/include/llvm/Transforms/Utils/UnifyFunctionExitNodes.h
@@ -19,8 +19,6 @@
 
 namespace llvm {
 
-class BasicBlock;
-
 class UnifyFunctionExitNodesLegacyPass : public FunctionPass {
 public:
   static char ID; // Pass identification, replacement for typeid