[AMDGPU] exclude r600 targets from NPM

Author: vikramRH

llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp

@@ -752,9 +752,6 @@ AMDGPUTargetMachine::AMDGPUTargetMachine(const Target &T, const Triple &TT,
       TLOF(createTLOF(getTargetTriple())) {
   initAsmInfo();
 
-  if (getSelectorType(*this) != SelectorType::GlobalISel)
-    setNewPMForBackend(true);
-
   if (TT.isAMDGCN()) {
     if (getMCSubtargetInfo()->checkFeatures("+wavefrontsize64"))
       MRI.reset(llvm::createGCNMCRegisterInfo(AMDGPUDwarfFlavour::Wave64));
@@ -1110,7 +1107,10 @@ GCNTargetMachine::GCNTargetMachine(const Target &T, const Triple &TT,
                                    std::optional<Reloc::Model> RM,
                                    std::optional<CodeModel::Model> CM,
                                    CodeGenOptLevel OL, bool JIT)
-    : AMDGPUTargetMachine(T, TT, CPU, FS, Options, RM, CM, OL) {}
+    : AMDGPUTargetMachine(T, TT, CPU, FS, Options, RM, CM, OL) {
+    if (getSelectorType(*this) != SelectorType::GlobalISel)
+        setNewPMForBackend(true);
+   }
 
 const TargetSubtargetInfo *
 GCNTargetMachine::getSubtargetImpl(const Function &F) const {