compiler: desugar x != y into not x == y (fixes #974).

artiq/compiler/transforms/artiq_ir_generator.py

@@ -1478,7 +1478,7 @@ class ARTIQIRGenerator(algorithm.Visitor):
         else:
             assert False
 
-    def polymorphic_compare_pair_inclusion(self, op, needle, haystack):
+    def polymorphic_compare_pair_inclusion(self, needle, haystack):
         if builtins.is_range(haystack.type):
             # Optimized range `in` operator
             start       = self.append(ir.GetAttr(haystack, "start"))
@@ -1522,21 +1522,29 @@ class ARTIQIRGenerator(algorithm.Visitor):
         else:
             assert False
 
-        if isinstance(op, ast.NotIn):
-            result = self.append(ir.Select(result,
-                        ir.Constant(False, builtins.TBool()),
-                        ir.Constant(True, builtins.TBool())))
-
         return result
 
+    def invert(self, value):
+        return self.append(ir.Select(value,
+                    ir.Constant(False, builtins.TBool()),
+                    ir.Constant(True, builtins.TBool())))
+
     def polymorphic_compare_pair(self, op, lhs, rhs):
         if isinstance(op, (ast.Is, ast.IsNot)):
             # The backend will handle equality of aggregates.
             return self.append(ir.Compare(op, lhs, rhs))
-        elif isinstance(op, (ast.In, ast.NotIn)):
-            return self.polymorphic_compare_pair_inclusion(op, lhs, rhs)
-        else: # Eq, NotEq, Lt, LtE, Gt, GtE
+        elif isinstance(op, ast.In):
+            return self.polymorphic_compare_pair_inclusion(lhs, rhs)
+        elif isinstance(op, ast.NotIn):
+            result = self.polymorphic_compare_pair_inclusion(lhs, rhs)
+            return self.invert(result)
+        elif isinstance(op, (ast.Eq, ast.Lt, ast.LtE, ast.Gt, ast.GtE)):
             return self.polymorphic_compare_pair_order(op, lhs, rhs)
+        elif isinstance(op, ast.NotEq):
+            result = self.polymorphic_compare_pair_order(ast.Eq(loc=op.loc), lhs, rhs)
+            return self.invert(result)
+        else:
+            assert False
 
     def visit_CompareT(self, node):
         # Essentially a sequence of `and`s performed over results