Only call TRI::getRawAllocationOrder to resolve a target-dependent hint.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@133313 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/RegAllocLinearScan.cpp b/lib/CodeGen/RegAllocLinearScan.cpp
index 0818034..7a2ea6c 100644
--- a/lib/CodeGen/RegAllocLinearScan.cpp
+++ b/lib/CodeGen/RegAllocLinearScan.cpp
@@ -1440,8 +1440,12 @@
   if (TargetRegisterInfo::isVirtualRegister(physReg) && vrm_->hasPhys(physReg))
     physReg = vrm_->getPhys(physReg);
 
-  ArrayRef<unsigned> Order = tri_->getRawAllocationOrder(RC, Hint.first,
-                                                         physReg, *mf_);
+  ArrayRef<unsigned> Order;
+  if (Hint.first)
+    Order = tri_->getRawAllocationOrder(RC, Hint.first, physReg, *mf_);
+  else
+    Order = RegClassInfo.getOrder(RC);
+
   assert(!Order.empty() && "No allocatable register in this register class!");
 
   // Scan for the first available register.