Move the DataLayout to the generic TargetMachine, making it mandatory.

Summary:
I don't know why every singled backend had to redeclare its own DataLayout.
There was a virtual getDataLayout() on the common base TargetMachine, the
default implementation returned nullptr. It was not clear from this that
we could assume at call site that a DataLayout will be available with
each Target.

Now getDataLayout() is no longer virtual and return a pointer to the
DataLayout member of the common base TargetMachine. I plan to turn it into
a reference in a future patch.

The only backend that didn't have a DataLayout previsouly was the CPPBackend.
It now initializes the default DataLayout. This commit is NFC for all the
other backends.

Test Plan: clang+llvm ninja check-all

Reviewers: echristo

Subscribers: jfb, jholewinski, llvm-commits

Differential Revision: http://reviews.llvm.org/D8243

From: Mehdi Amini <mehdi.amini@apple.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231987 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/TargetMachine.cpp

@@ -36,14 +36,12 @@ using namespace llvm;
 // TargetMachine Class
 //
 
-TargetMachine::TargetMachine(const Target &T,
+TargetMachine::TargetMachine(const Target &T, StringRef DataLayoutString,
                              StringRef TT, StringRef CPU, StringRef FS,
                              const TargetOptions &Options)
-  : TheTarget(T), TargetTriple(TT), TargetCPU(CPU), TargetFS(FS),
-    CodeGenInfo(nullptr), AsmInfo(nullptr),
-    RequireStructuredCFG(false),
-    Options(Options) {
-}
+    : TheTarget(T), DL(DataLayoutString), TargetTriple(TT), TargetCPU(CPU),
+      TargetFS(FS), CodeGenInfo(nullptr), AsmInfo(nullptr),
+      RequireStructuredCFG(false), Options(Options) {}
 
 TargetMachine::~TargetMachine() {
   delete CodeGenInfo;