Accept null PhysReg arguments to checkRegMaskInterference.

Calling checkRegMaskInterference(VirtReg) checks if VirtReg crosses any
regmask operands, regardless of the registers they clobber.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@158563 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LiveRegMatrix.h b/lib/CodeGen/LiveRegMatrix.h
index 4c3e7d4..019a5f5 100644
--- a/lib/CodeGen/LiveRegMatrix.h
+++ b/lib/CodeGen/LiveRegMatrix.h
@@ -124,7 +124,8 @@
 
   /// Check for regmask interference only.
   /// Return true if VirtReg crosses a regmask operand that clobbers PhysReg.
-  bool checkRegMaskInterference(LiveInterval &VirtReg, unsigned PhysReg);
+  /// If PhysReg is null, check if VirtReg crosses any regmask operands.
+  bool checkRegMaskInterference(LiveInterval &VirtReg, unsigned PhysReg = 0);
 
   /// Check for regunit interference only.
   /// Return true if VirtReg overlaps a fixed assignment of one of PhysRegs's