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>
llvm-svn: 231987
diff --git a/llvm/lib/Target/NVPTX/NVPTXTargetMachine.cpp b/llvm/lib/Target/NVPTX/NVPTXTargetMachine.cpp
index e1726fc..2e362a6 100644
--- a/llvm/lib/Target/NVPTX/NVPTXTargetMachine.cpp
+++ b/llvm/lib/Target/NVPTX/NVPTXTargetMachine.cpp
@@ -88,9 +88,10 @@
                                        const TargetOptions &Options,
                                        Reloc::Model RM, CodeModel::Model CM,
                                        CodeGenOpt::Level OL, bool is64bit)
-    : LLVMTargetMachine(T, TT, CPU, FS, Options, RM, CM, OL), is64bit(is64bit),
-      TLOF(make_unique<NVPTXTargetObjectFile>()),
-      DL(computeDataLayout(is64bit)), Subtarget(TT, CPU, FS, *this) {
+    : LLVMTargetMachine(T, computeDataLayout(is64bit), TT, CPU, FS, Options, RM,
+                        CM, OL),
+      is64bit(is64bit), TLOF(make_unique<NVPTXTargetObjectFile>()),
+      Subtarget(TT, CPU, FS, *this) {
   if (Triple(TT).getOS() == Triple::NVCL)
     drvInterface = NVPTX::NVCL;
   else