[TM] Start collapsing LLVMTargetMachine into TargetMachine

[davide]

Summary

As already discussed in the review that lead to the removal of the CppBackend, it seems to be a good idea to merge LLVMTargetMachine and TargetMachine together. This patch is a first step, hopefully correct.
To put things into perspective, this work is (at least partly) motivated by the desire to make TargetMachine thread-safe, so that we can simplify the splitCodeGen() logic currently used by LTO. While the two projects may be considered orthogonal, I prefer to tackle this yak shaving.

[• rafael]

Given the library dependencies I would assume the final version has to live in lib/CodeGen, no?

lib/Target/TargetMachine.cpp

151

Can you change this to be non-virtual now?

[davide]

lib/Target/TargetMachine.cpp

151

Not entirely sure because PPC and Hexagon still override that? Can we somehow avoid it?

../lib/Target/PowerPC/PPCTargetMachine.h:48:42: error: only virtual member functions can be marked 'override'
  TargetIRAnalysis getTargetIRAnalysis() override;
                                         ^~~~~~~~

[davide]

This one currently breaks SHARED_LIBS. I'll try to get back to this soon.

include/llvm/Target/TargetMachine.h

 protected: // Can only create subclasses.
   LLVMTargetMachine(const Target &T, StringRef DataLayoutString,
                     const Triple &TargetTriple, StringRef CPU, StringRef FS,
                     TargetOptions Options, Reloc::Model RM, CodeModel::Model CM,
                     CodeGenOpt::Level OL);
 
   void initAsmInfo();
 public:
-  /// \brief Get a TargetIRAnalysis implementation for the target.
-  ///
-  /// This analysis will produce a TTI result which uses the common code
-  /// generator to answer queries about the IR.
-  TargetIRAnalysis getTargetIRAnalysis() override;
-
   /// Create a pass configuration object to be used by addPassToEmitX methods
   /// for generating a pipeline of CodeGen passes.
   virtual TargetPassConfig *createPassConfig(PassManagerBase &PM);
 
   /// Add passes to the specified pass manager to get the specified file
   /// emitted.  Typically this will involve several steps of code generation.
   bool addPassesToEmitFile(
       PassManagerBase &PM, raw_pwrite_stream &Out, CodeGenFileType FileType,

lib/CodeGen/LLVMTargetMachine.cpp

LLVMTargetMachine::LLVMTargetMachine(const Target &T,
                                      const Triple &TT, StringRef CPU,
                                      StringRef FS, TargetOptions Options,
                                      Reloc::Model RM, CodeModel::Model CM,
                                      CodeGenOpt::Level OL)
     : TargetMachine(T, DataLayoutString, TT, CPU, FS, Options) {
   CodeGenInfo = T.createMCCodeGenInfo(TT.str(), RM, CM, OL);
 }
 
-TargetIRAnalysis LLVMTargetMachine::getTargetIRAnalysis() {
-  return TargetIRAnalysis([this](const Function &F) {
-    return TargetTransformInfo(BasicTTIImpl(this, F));
-  });
-}
-
 MachineModuleInfo &
 LLVMTargetMachine::addMachineModuleInfo(PassManagerBase &PM) const {
   MachineModuleInfo *MMI = new MachineModuleInfo(*getMCAsmInfo(),
                                                  *getMCRegisterInfo(),
                                                  getObjFileLowering());
   PM.add(MMI);
   return *MMI;
 }

lib/Target/TargetMachine.cpp

 //===-- TargetMachine.cpp - General Target Information ---------------------==//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file describes the general parts of a Target machine.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Analysis/TargetTransformInfo.h"
+#include "llvm/CodeGen/BasicTTIImpl.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/GlobalAlias.h"
 #include "llvm/IR/GlobalValue.h"
 #include "llvm/IR/GlobalVariable.h"
 #include "llvm/IR/LegacyPassManager.h"
 #include "llvm/IR/Mangler.h"
 #include "llvm/MC/MCAsmInfo.h"
CodeGenOpt::Level TargetMachine::getOptLevel() const {
   return CodeGenInfo->getOptLevel();
 }
 
 void TargetMachine::setOptLevel(CodeGenOpt::Level Level) const {
   if (CodeGenInfo)
     CodeGenInfo->setOptLevel(Level);
 }
 
 TargetIRAnalysis TargetMachine::getTargetIRAnalysis() {
   return TargetIRAnalysis([this](const Function &F) {
-    return TargetTransformInfo(F.getParent()->getDataLayout());
+    return TargetTransformInfo(BasicTTIImpl(this, F));
   });
 }
 
 void TargetMachine::getNameWithPrefix(SmallVectorImpl<char> &Name,
                                       const GlobalValue *GV, Mangler &Mang,
                                       bool MayAlwaysUsePrivate) const {
   if (MayAlwaysUsePrivate || !GV->hasPrivateLinkage()) {
     // Simple case: If GV is not private, it is not important to find out if