Cleanups in AArch64 (#168025)

Forward declare a couple of classes for simplicity, remove some unused
headers, clean up a comment.

Tested with check-all.

Author: echristo

llvm/include/llvm/CodeGen/GlobalISel/GIMatchTableExecutorImpl.h

@@ -25,16 +25,13 @@
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/RegisterBankInfo.h"
 #include "llvm/CodeGen/TargetInstrInfo.h"
-#include "llvm/CodeGen/TargetOpcodes.h"
 #include "llvm/CodeGen/TargetRegisterInfo.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/Type.h"
 #include "llvm/Support/CodeGenCoverage.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
-#include "llvm/Support/LEB128.h"
-#include "llvm/Support/raw_ostream.h"
 #include <cassert>
 #include <cstddef>
 #include <cstdint>

llvm/lib/Target/AArch64/AArch64.h

@@ -26,8 +26,10 @@ namespace llvm {
 class AArch64RegisterBankInfo;
 class AArch64Subtarget;
 class AArch64TargetMachine;
+enum class CodeGenOptLevel;
 class FunctionPass;
 class InstructionSelector;
+class ModulePass;
 
 FunctionPass *createAArch64DeadRegisterDefinitions();
 FunctionPass *createAArch64RedundantCopyEliminationPass();

llvm/lib/Target/AArch64/AArch64LoadStoreOptimizer.cpp

@@ -42,7 +42,6 @@
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/DebugCounter.h"
 #include "llvm/Support/ErrorHandling.h"
-#include "llvm/Support/raw_ostream.h"
 #include <cassert>
 #include <cstdint>
 #include <functional>

llvm/lib/Target/AArch64/AArch64MacroFusion.h

@@ -23,6 +23,6 @@ namespace llvm {
 /// to AArch64TargetMachine::createMachineScheduler() to have an effect.
 std::unique_ptr<ScheduleDAGMutation> createAArch64MacroFusionDAGMutation();
 
-} // llvm
+} // namespace llvm
 
 #endif // LLVM_LIB_TARGET_AARCH64_AARCH64MACROFUSION_H

llvm/lib/Target/AArch64/AArch64TargetMachine.cpp

@@ -53,7 +53,6 @@
 #include "llvm/Transforms/Utils/LowerIFunc.h"
 #include "llvm/Transforms/Vectorize/LoopIdiomVectorize.h"
 #include <memory>
-#include <optional>
 
 using namespace llvm;
 

llvm/lib/Target/X86/X86Subtarget.cpp

@@ -32,7 +32,6 @@
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
-#include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/TargetParser/Triple.h"