[MachineOutliner] Freeze registers in new functions

[gberry]

Summary

Call MRI.freezeReservedRegs() on functions created during outlining so
that calls to isReserved() by the verifier called after this pass won't
assert.

[paquette]

LGTM

lib/CodeGen/MachineOutliner.cpp

 ///
 //===----------------------------------------------------------------------===//
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineModuleInfo.h"
 #include "llvm/CodeGen/MachineOptimizationRemarkEmitter.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/Passes.h"
 #include "llvm/CodeGen/TargetInstrInfo.h"
 #include "llvm/CodeGen/TargetRegisterInfo.h"
 #include "llvm/CodeGen/TargetSubtargetInfo.h"
 #include "llvm/IR/DIBuilder.h"
 #include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/Mangler.h"
 #include "llvm/Support/Allocator.h"
for (Function *F : CreatedIRFunctions) {
       // Attach subprogram to the function.
       F->setSubprogram(SP);
     }
 
     // We're done with the DIBuilder.
     DB.finalize();
   }
 
+  MF.getRegInfo().freezeReservedRegs(MF);
   return &MF;
 }
 
 bool MachineOutliner::outline(
     Module &M, const ArrayRef<std::shared_ptr<Candidate>> &CandidateList,
     std::vector<OutlinedFunction> &FunctionList, InstructionMapper &Mapper) {
 
   bool OutlinedSomething = false;

test/CodeGen/AArch64/machine-outliner.mir

-# RUN: llc -mtriple=aarch64--- -run-pass=machine-outliner %s -o - | FileCheck %s
+# RUN: llc -mtriple=aarch64--- -run-pass=machine-outliner -verify-machineinstrs %s -o - | FileCheck %s
 --- |
 
   @x = common global i32 0, align 4
 
   define void @baz() #0 {
     ret void
   }