Assert that the target provided hints are in the allocation order.

Target implementations of getRegAllocationHints() should use the
provided allocation order, and they can never return hints outside the
order. This is already documented in TargetRegisterInfo.h.

<rdar://problem/13240556>

llvm-svn: 175540
diff --git a/llvm/lib/CodeGen/AllocationOrder.cpp b/llvm/lib/CodeGen/AllocationOrder.cpp
index 1d09d20f..3fa1f8f 100644
--- a/llvm/lib/CodeGen/AllocationOrder.cpp
+++ b/llvm/lib/CodeGen/AllocationOrder.cpp
@@ -44,4 +44,9 @@
       dbgs() << '\n';
     }
   });
+#ifndef NDEBUG
+  for (unsigned I = 0, E = Hints.size(); I != E; ++I)
+    assert(std::find(Order.begin(), Order.end(), Hints[I]) != Order.end() &&
+           "Target hint is outside allocation order.");
+#endif
 }