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/Mips/MipsTargetMachine.cpp b/llvm/lib/Target/Mips/MipsTargetMachine.cpp
index 86c8931..be08136 100644
--- a/llvm/lib/Target/Mips/MipsTargetMachine.cpp
+++ b/llvm/lib/Target/Mips/MipsTargetMachine.cpp
@@ -46,8 +46,12 @@
   RegisterTargetMachine<MipselTargetMachine> B(TheMips64elTarget);
 }
 
-static std::string computeDataLayout(bool isLittle, MipsABIInfo &ABI) {
+static std::string computeDataLayout(StringRef TT, StringRef CPU,
+                                     const TargetOptions &Options,
+                                     bool isLittle) {
   std::string Ret = "";
+  MipsABIInfo ABI =
+      MipsABIInfo::computeTargetABI(Triple(TT), CPU, Options.MCOptions);
 
   // There are both little and big endian mips.
   if (isLittle)
@@ -86,11 +90,11 @@
                                      const TargetOptions &Options,
                                      Reloc::Model RM, CodeModel::Model CM,
                                      CodeGenOpt::Level OL, bool isLittle)
-    : LLVMTargetMachine(T, TT, CPU, FS, Options, RM, CM, OL),
+    : LLVMTargetMachine(T, computeDataLayout(TT, CPU, Options, isLittle), TT,
+                        CPU, FS, Options, RM, CM, OL),
       isLittle(isLittle), TLOF(make_unique<MipsTargetObjectFile>()),
       ABI(MipsABIInfo::computeTargetABI(Triple(TT), CPU, Options.MCOptions)),
-      DL(computeDataLayout(isLittle, ABI)), Subtarget(nullptr),
-      DefaultSubtarget(TT, CPU, FS, isLittle, *this),
+      Subtarget(nullptr), DefaultSubtarget(TT, CPU, FS, isLittle, *this),
       NoMips16Subtarget(TT, CPU, FS.empty() ? "-mips16" : FS.str() + ",-mips16",
                         isLittle, *this),
       Mips16Subtarget(TT, CPU, FS.empty() ? "+mips16" : FS.str() + ",+mips16",