Remove the target independent TargetMachine::getSubtarget and

TargetMachine::getSubtargetImpl routines.

This keeps the target independent code free of bare subtarget
calls while the remainder of the backends are migrated, or not
if they don't wish to support per-function subtargets as would
be needed for function multiversioning or LTO of disparate
cpu subarchitecture types, e.g.

clang -msse4.2 -c foo.c -emit-llvm -o foo.bc
clang -c bar.c -emit-llvm -o bar.bc
llvm-link foo.bc bar.bc -o baz.bc
llc baz.bc

and get appropriate code for what the command lines requested.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232885 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/XCore/XCoreTargetMachine.h

@@ -29,7 +29,10 @@ public:
                      CodeGenOpt::Level OL);
   ~XCoreTargetMachine() override;
 
-  const XCoreSubtarget *getSubtargetImpl() const override { return &Subtarget; }
+  const XCoreSubtarget *getSubtargetImpl() const { return &Subtarget; }
+  const XCoreSubtarget *getSubtargetImpl(const Function &) const override {
+    return &Subtarget;
+  }
 
   // Pass Pipeline Configuration
   TargetPassConfig *createPassConfig(PassManagerBase &PM) override;