diff --git a/llvm/include/llvm/CodeGen/TargetRegisterInfo.h b/llvm/include/llvm/CodeGen/TargetRegisterInfo.h
--- a/llvm/include/llvm/CodeGen/TargetRegisterInfo.h
+++ b/llvm/include/llvm/CodeGen/TargetRegisterInfo.h
@@ -1076,6 +1076,14 @@
     return false;
   }
 
+  /// When prioritizing live ranges in register allocation, if this hook returns
+  /// true then the AllocationPriority of the register class will be treated as
+  /// more important than whether the range is local to a basic block or global.
+  virtual bool
+  regClassPriorityTrumpsGlobalness(const MachineFunction &MF) const {
+    return false;
+  }
+
   //===--------------------------------------------------------------------===//
   /// Debug information queries.
 
diff --git a/llvm/lib/CodeGen/RegAllocGreedy.h b/llvm/lib/CodeGen/RegAllocGreedy.h
--- a/llvm/lib/CodeGen/RegAllocGreedy.h
+++ b/llvm/lib/CodeGen/RegAllocGreedy.h
@@ -322,6 +322,10 @@
   /// Function
   ArrayRef<uint8_t> RegCosts;
 
+  /// Flags for the live range priority calculation, determined once per
+  /// machine function.
+  bool RegClassPriorityTrumpsGlobalness;
+
 public:
   RAGreedy(const RegClassFilterFunc F = allocateAllRegClasses);
 
diff --git a/llvm/lib/CodeGen/RegAllocGreedy.cpp b/llvm/lib/CodeGen/RegAllocGreedy.cpp
--- a/llvm/lib/CodeGen/RegAllocGreedy.cpp
+++ b/llvm/lib/CodeGen/RegAllocGreedy.cpp
@@ -305,6 +305,7 @@
     const TargetRegisterClass &RC = *MRI->getRegClass(Reg);
     bool ForceGlobal = !ReverseLocal &&
       (Size / SlotIndex::InstrDist) > (2 * RCI.getNumAllocatableRegs(&RC));
+    unsigned GlobalBit = 0;
 
     if (Stage == RS_Assign && !ForceGlobal && !LI->empty() &&
         LIS->intervalIsInOneMBB(*LI)) {
@@ -323,9 +324,13 @@
       // Allocate global and split ranges in long->short order. Long ranges that
       // don't fit should be spilled (or split) ASAP so they don't create
       // interference.  Mark a bit to prioritize global above local ranges.
-      Prio = (1u << 29) + Size;
+      Prio = Size;
+      GlobalBit = 1;
     }
-    Prio |= RC.AllocationPriority << 24;
+    if (RegClassPriorityTrumpsGlobalness)
+      Prio |= RC.AllocationPriority << 25 | GlobalBit << 24;
+    else
+      Prio |= GlobalBit << 29 | RC.AllocationPriority << 24;
 
     // Mark a higher bit to prioritize global and local above RS_Split.
     Prio |= (1u << 31);
@@ -2692,6 +2697,7 @@
   initializeCSRCost();
 
   RegCosts = TRI->getRegisterCosts(*MF);
+  RegClassPriorityTrumpsGlobalness = TRI->regClassPriorityTrumpsGlobalness(*MF);
 
   ExtraInfo.emplace();
   EvictAdvisor =