diff --git a/llvm/lib/CodeGen/RegisterClassInfo.cpp b/llvm/lib/CodeGen/RegisterClassInfo.cpp
--- a/llvm/lib/CodeGen/RegisterClassInfo.cpp
+++ b/llvm/lib/CodeGen/RegisterClassInfo.cpp
@@ -188,6 +188,8 @@
   }
   assert(RC && "Failed to find register class");
   compute(RC);
+  if (getNumAllocatableRegs(RC) == 0)
+    return TRI->getRegPressureSetLimit(*MF, Idx);
   unsigned NReserved = RC->getNumRegs() - getNumAllocatableRegs(RC);
   return TRI->getRegPressureSetLimit(*MF, Idx) -
          TRI->getRegClassWeight(RC).RegWeight * NReserved;
diff --git a/llvm/test/CodeGen/PowerPC/compute-regpressure.ll b/llvm/test/CodeGen/PowerPC/compute-regpressure.ll
--- a/llvm/test/CodeGen/PowerPC/compute-regpressure.ll
+++ b/llvm/test/CodeGen/PowerPC/compute-regpressure.ll
@@ -1,7 +1,7 @@
 ; REQUIRES: asserts
 ; RUN: llc -debug-only=regalloc < %s 2>&1 |FileCheck %s --check-prefix=DEBUG
 
-; DEBUG-COUNT-3:         AllocationOrder(VRSAVERC) = [ ]
+; DEBUG-COUNT-1:         AllocationOrder(VRSAVERC) = [ ]
 
 target triple = "powerpc64le-unknown-linux-gnu"