diff: additions to const_prop.m

[Simon Taylor]

Estimated hours taken: 0.1

compiler/const_prop.m:
	Optimize `int:unchecked_left_shift/2', `int:unchecked_right_shift/2'
	and `int:rem/2'.
	Note: the bug with division by zero for `rem' and `mod' is fixed in
	my next commit.

Index: const_prop.m
===================================================================
RCS file: /home/staff/zs/imp/mercury/compiler/const_prop.m,v
retrieving revision 1.6
diff -u -u -r1.6 const_prop.m
--- const_prop.m	1998/11/20 04:07:14	1.6
+++ const_prop.m	1999/03/30 05:34:53
@@ -191,16 +191,36 @@
 	YVal is XVal // ZVal.
 ****/
 
+	% This isn't actually a builtin.
 evaluate_builtin_tri("int", "mod", 0, X, Y, Z, Z, int_const(ZVal)) :-
 	X = _XVar - bound(_XUniq, [functor(int_const(XVal), [])]),
 	Y = _YVar - bound(_YUniq, [functor(int_const(YVal), [])]),
 	ZVal is XVal mod YVal.
 
+evaluate_builtin_tri("int", "rem", 0, X, Y, Z, Z, int_const(ZVal)) :-
+	X = _XVar - bound(_XUniq, [functor(int_const(XVal), [])]),
+	Y = _YVar - bound(_YUniq, [functor(int_const(YVal), [])]),
+	ZVal is XVal rem YVal.
+
+evaluate_builtin_tri("int", "unchecked_left_shift",
+		0, X, Y, Z, Z, int_const(ZVal)) :-
+	X = _XVar - bound(_XUniq, [functor(int_const(XVal), [])]),
+	Y = _YVar - bound(_YUniq, [functor(int_const(YVal), [])]),
+	ZVal is unchecked_left_shift(XVal, YVal).
+
+	% This isn't actually a builtin.
 evaluate_builtin_tri("int", "<<", 0, X, Y, Z, Z, int_const(ZVal)) :-
 	X = _XVar - bound(_XUniq, [functor(int_const(XVal), [])]),
 	Y = _YVar - bound(_YUniq, [functor(int_const(YVal), [])]),
 	ZVal is XVal << YVal.
 
+evaluate_builtin_tri("int", "unchecked_right_shift",
+		0, X, Y, Z, Z, int_const(ZVal)) :-
+	X = _XVar - bound(_XUniq, [functor(int_const(XVal), [])]),
+	Y = _YVar - bound(_YUniq, [functor(int_const(YVal), [])]),
+	ZVal is unchecked_right_shift(XVal, YVal).
+
+	% This isn't actually a builtin.
 evaluate_builtin_tri("int", ">>", 0, X, Y, Z, Z, int_const(ZVal)) :-
 	X = _XVar - bound(_XUniq, [functor(int_const(XVal), [])]),
 	Y = _YVar - bound(_YUniq, [functor(int_const(YVal), [])]),