[LVN] Add logical operators to foldable, a few special cases.

examples/lvn.py

@@ -199,6 +199,9 @@ def _lookup(value2num, value):
     'le': lambda a, b: a <= b,
     'ne': lambda a, b: a != b,
     'eq': lambda a, b: a == b,
+    'or': lambda a, b: a or b,
+    'and': lambda a, b: a and b,
+    'not': lambda a: not a
 }
 
 
@@ -212,6 +215,14 @@ def _fold(num2const, value):
                 # Equivalent arguments may be evaluated for equality.
                 # E.g. `eq x x`, where `x` is not a constant evaluates to `true`.
                 return value.op != 'ne'
+
+            if value.op in {'and', 'or'} and any(v in num2const for v in value.args):
+                # Short circuiting the logical operators `and` and `or` for two cases:
+                # (1) `and x c0` -> false, where `c0` a constant that evaluates to `false`.
+                # (2) `or x c1`  -> true, where `c1` a constant that evaluates to `true`.
+                const_val = num2const[value.args[0] if value.args[0] in num2const else value.args[1]]
+                if (value.op == 'and' and not const_val) or (value.op == 'or' and const_val):
+                    return const_val
             return None
         except ZeroDivisionError:  # If we hit a dynamic error, bail!
             return None

examples/test/lvn/logical-operators.bril

@@ -0,0 +1,26 @@
+# ARGS: -f
+
+@main(arg1: bool, arg2: bool) {
+  t: int = const true;
+  f: int = const false;
+
+  constant_fold1: bool = and f t;
+  constant_fold2: bool = and t f;
+  constant_fold3: bool = or t f;
+  constant_fold4: bool = or f t;
+  constant_fold5: bool = not t;
+  constant_fold6: bool = not f;
+
+  should_fold1: bool = and f arg1;
+  should_fold2: bool = and arg1 f;
+  should_fold3: bool = or t arg1;
+  should_fold4: bool = or arg1 t;
+
+  no_fold1: bool = and t arg1;
+  no_fold2: bool = and arg1 t;
+  no_fold3: bool = or f arg1;
+  no_fold4: bool = or arg1 f;
+  no_fold5: bool = and arg1 arg2;
+  no_fold6: bool = or arg1 arg2;
+  no_fold7: bool = not arg1;
+}

examples/test/lvn/logical-operators.out

@@ -0,0 +1,21 @@
+@main(arg1: bool, arg2: bool) {
+  t: int = const true;
+  f: int = const false;
+  constant_fold1: bool = const false;
+  constant_fold2: bool = const false;
+  constant_fold3: bool = const true;
+  constant_fold4: bool = const true;
+  constant_fold5: bool = const false;
+  constant_fold6: bool = const true;
+  should_fold1: bool = const false;
+  should_fold2: bool = const false;
+  should_fold3: bool = const true;
+  should_fold4: bool = const true;
+  no_fold1: bool = and t arg1;
+  no_fold2: bool = and arg1 t;
+  no_fold3: bool = or f arg1;
+  no_fold4: bool = or arg1 f;
+  no_fold5: bool = and arg1 arg2;
+  no_fold6: bool = or arg1 arg2;
+  no_fold7: bool = not arg1;
+}