[iwyu] Fix some header include regression

[serge-sans-paille]

Summary

Running iwyu-diff from https://github.com/serge-sans-paille/preprocessor-utils makes it possible to quickly spot regression in unused includes. This patch contains the few regressions since the last header cleanup.

[MaskRay]

LGTM.

llvm/lib/IR/FPEnv.cpp

 //===-- FPEnv.cpp ---- FP Environment -------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 /// @file
 /// This file contains the implementations of entities that describe floating
 /// point environment.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/IR/FPEnv.h"
 #include "llvm/ADT/StringSwitch.h"
-#include "llvm/IR/InstrTypes.h"
+#include "llvm/IR/Instruction.h"
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/Intrinsics.h"
 
 namespace llvm {
 
 Optional<RoundingMode> convertStrToRoundingMode(StringRef RoundingArg) {
   // For dynamic rounding mode, we use round to nearest but we will set the
   // 'exact' SDNodeFlag so that the value will not be rounded.

llvm/lib/Target/MSP430/MSP430ISelDAGToDAG.cpp

 #include "MSP430.h"
 #include "MSP430TargetMachine.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/SelectionDAG.h"
 #include "llvm/CodeGen/SelectionDAGISel.h"
-#include "llvm/CodeGen/TargetLowering.h"
 #include "llvm/Config/llvm-config.h"
 #include "llvm/IR/CallingConv.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/Intrinsics.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"

llvm/lib/Target/NVPTX/NVPTXAsmPrinter.cpp

 #include "llvm/CodeGen/MachineBasicBlock.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineInstr.h"
 #include "llvm/CodeGen/MachineLoopInfo.h"
 #include "llvm/CodeGen/MachineModuleInfo.h"
 #include "llvm/CodeGen/MachineOperand.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
-#include "llvm/CodeGen/TargetLowering.h"
 #include "llvm/CodeGen/TargetRegisterInfo.h"
 #include "llvm/CodeGen/ValueTypes.h"
 #include "llvm/IR/Attributes.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/Constant.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/DebugInfo.h"

llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp

 #include "llvm/CodeGen/TargetCallingConv.h"
 #include "llvm/CodeGen/TargetLowering.h"
 #include "llvm/CodeGen/ValueTypes.h"
 #include "llvm/IR/Argument.h"
 #include "llvm/IR/Attributes.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/FPEnv.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/GlobalValue.h"
 #include "llvm/IR/Instruction.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/IntrinsicsNVPTX.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/Type.h"
 #include "llvm/IR/Value.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/CodeGen.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/MachineValueType.h"
-#include "llvm/Support/MathExtras.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Target/TargetOptions.h"
 #include <algorithm>
 #include <cassert>
 #include <cstdint>
 #include <iterator>
 #include <sstream>

llvm/lib/Transforms/Scalar/Float2Int.cpp

 #include "llvm/IR/Module.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/Pass.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Transforms/Scalar.h"
 #include <deque>
-#include <functional> // For std::function
 
 #define DEBUG_TYPE "float2int"
 
 using namespace llvm;
 
 // The algorithm is simple. Start at instructions that convert from the
 // float to the int domain: fptoui, fptosi and fcmp. Walk up the def-use
 // graph, using an equivalence datastructure to unify graphs that interfere.