[SystemZ] Add basic prefetch support

Just the instructions and intrinsics for now.

llvm-svn: 189100
diff --git a/llvm/lib/Target/SystemZ/SystemZ.h b/llvm/lib/Target/SystemZ/SystemZ.h
index bb6ceac..ea6c7d1 100644
--- a/llvm/lib/Target/SystemZ/SystemZ.h
+++ b/llvm/lib/Target/SystemZ/SystemZ.h
@@ -57,6 +57,10 @@
     const unsigned CCMASK_SRST_NOTFOUND = CCMASK_2;
     const unsigned CCMASK_SRST          = CCMASK_1 | CCMASK_2;
 
+    // Mask assignments for PFD.
+    const unsigned PFD_READ  = 1;
+    const unsigned PFD_WRITE = 2;
+
     // Return true if Val fits an LLILL operand.
     static inline bool isImmLL(uint64_t Val) {
       return (Val & ~0x000000000000ffffULL) == 0;