added add delta

CHERICC_Fat.bsv

@@ -38,6 +38,7 @@ export CapReg;
 export CapPipe;
 
 export encodeDelta;
+export addDelta;
 export decodeDelta;
 
 export CapFat;
@@ -1185,6 +1186,7 @@ instance CHERICap #(CapMem, OTypeW, FlagsW, CapAddrW, CapW, TSub #(MW, 3));
   function isDerivable = error ("isDerivable not implemented for CapMem");
 
   function encodeDelta (cap, delta) = error ("encode delta not implemented");
+  function addDelta (cap, delta) = error ("addDelta not implemented");
   function decodeDelta (cap) = error ("decode delta not implemented");
 
 endinstance
@@ -1342,6 +1344,7 @@ instance CHERICap #(CapReg, OTypeW, FlagsW, CapAddrW, CapW, TSub #(MW, 3));
   function setBoundsCombined (cap, length) = error ("setBoundsCombined not implemented for CapReg");
 
   function encodeDelta (cap, delta) = error ("encode delta not implemented");
+  function addDelta (cap, delta) = error ("addDelta not implemented");
   function decodeDelta (cap) = error ("decode delta not implemented");
 
   //function setBounds = error ("setBounds not implemented for CapReg");
@@ -1428,6 +1431,13 @@ instance CHERICap #(CapPipe, OTypeW, FlagsW, CapAddrW, CapW, TSub#(MW, 3));
     cap.capFat.address = {d, va_bits};
     return cap;
   endfunction
+
+  function addDelta(cap, delta);
+    Bit#(25) d = truncate(delta);
+    cap.capFat.address = cap.capFat.address + zeroExtend(delta);
+    return cap;
+  endfunction
+
   
   // Extract the delta stored in bits 63:39 of the address
   function decodeDelta(cap);

CHERICap.bsv

@@ -173,6 +173,7 @@ typeclass CHERICap #( type capT              // type of the CHERICap capability
   function capT setFlags (capT cap, Bit #(flgW) flags);
 
   function capT encodeDelta(capT cap, Bit #(64) delta);
+  function capT addDelta(capT cap, Bit #(25) delta);
 
   function Bit #(25) decodeDelta(capT cap);