[m-rev.] diff: add reverse modes for uint.xor/2 (part 1)

[Julien Fischer]

Add reverse modes for uint.xor/2 (part 1).

compiler/builtin_ops.m:
      Implement the reverse modes for uint.xor/1 as builtins.

library/uint.m:
      Add the declarations for the reverse modes (commented out
      until this change has bootstrapped).

Julien.

diff --git a/compiler/builtin_ops.m b/compiler/builtin_ops.m
index e19eee9c1..6b1f40fcf 100644
--- a/compiler/builtin_ops.m
+++ b/compiler/builtin_ops.m
@@ -432,7 +432,6 @@ builtin_translation(ModuleName, PredName, ProcNum, Args, Code) :-
              ; PredName = "unchecked_rem", ArithOp = uint_mod
              ; PredName = "/\\", ArithOp = uint_bitwise_and
              ; PredName = "\\/", ArithOp = uint_bitwise_or
-            ; PredName = "xor", ArithOp = uint_bitwise_xor
              ; PredName = "unchecked_left_shift",
                  ArithOp = uint_unchecked_left_shift
              ; PredName = "unchecked_right_shift",
@@ -442,6 +441,19 @@ builtin_translation(ModuleName, PredName, ProcNum, Args, Code) :-
              Args = [X, Y, Z],
              Code = assign(Z, binary(ArithOp, leaf(X), leaf(Y)))
          ;
+            PredName = "xor",
+            Args = [X, Y, Z],
+            (
+                ProcNum = 0,
+                Code = assign(Z, binary(uint_bitwise_xor, leaf(X), leaf(Y)))
+            ;
+                ProcNum = 1,
+                Code = assign(Y, binary(uint_bitwise_xor, leaf(X), leaf(Z)))
+            ;
+                ProcNum = 2,
+                Code = assign(X, binary(uint_bitwise_xor, leaf(Y), leaf(Z)))
+            )
+        ;
              ( PredName = ">", CompareOp = uint_gt
              ; PredName = "<", CompareOp = uint_lt
              ; PredName = ">=", CompareOp = uint_ge
diff --git a/library/uint.m b/library/uint.m
index 2ebee22e2..5f1776b9b 100644
--- a/library/uint.m
+++ b/library/uint.m
@@ -161,7 +161,10 @@

      % Bitwise exclusive or (xor).
      %
-:- func xor(uint::in, uint::in) = (uint::uo) is det.
+:- func xor(uint, uint) = uint.
+:- mode xor(in, in) = uo is det.
+%:- mode xor(in, uo) = in is det.
+%:- mode xor(uo, in) = in is det.

      % Bitwise complement.
      %