Handle CF_BOOL_NEGATE in simplify_cfg (#489)

src/simplify_cfg.c

@@ -109,6 +109,19 @@ static void update_statuses_with_instruction(const CfGraph *cfg, enum VarStatus
         statuses[find_var_index(cfg, ins->operands[0])] = VS_UNPREDICTABLE;
         statuses[destidx] = VS_DEFINED;
         break;
+    case CF_BOOL_NEGATE:
+        switch(statuses[find_var_index(cfg, ins->operands[0])]) {
+            case VS_TRUE:
+                statuses[destidx] = VS_FALSE;
+                break;
+            case VS_FALSE:
+                statuses[destidx] = VS_TRUE;
+                break;
+            default:
+                statuses[destidx] = VS_DEFINED;
+                break;
+        }
+        break;
     case CF_CONSTANT:
         if (ins->data.constant.kind == CONSTANT_BOOL)
             statuses[destidx] = ins->data.constant.data.boolean ? VS_TRUE : VS_FALSE;

tests/other_errors/assert_fail.jou

@@ -4,5 +4,4 @@ def main() -> int:
     assert lol and wat
     assert lol and not wat  # Output: Assertion 'lol and not wat' failed in file "tests/other_errors/assert_fail.jou", line 5.
 
-    # TODO: Compiler should be clever enough to not warn about missing return statement, but it isn't.
-    return 0
+    # No need for a "return 0" because compiler knows we will never get here.

tests/other_errors/assert_fail_multiline.jou

@@ -6,5 +6,4 @@ def main() -> int:
         and not wat
     )
 
-    # TODO: Compiler should be clever enough to not warn about missing return statement, but it isn't.
-    return 0
+    # No need for a "return 0" because compiler knows we will never get here.

tests/should_succeed/and_or_not.jou

@@ -59,12 +59,10 @@ def main() -> int:
     printf("%d", False or False or False)
     printf("\n")
 
-    # TODO: presumably these should emit warnings too
-
     # Output: Precedence and 0001
     printf("Precedence and ")
-    printf("%d", not True and not True)
-    printf("%d", not True and not False)
+    printf("%d", not True and not True)  # Warning: this code will never run
+    printf("%d", not True and not False)  # Warning: this code will never run
     printf("%d", not False and not True)
     printf("%d", not False and not False)
     printf("\n")
@@ -73,8 +71,8 @@ def main() -> int:
     printf("Precedence or ")
     printf("%d", not True or not True)
     printf("%d", not True or not False)
-    printf("%d", not False or not True)
-    printf("%d", not False or not False)
+    printf("%d", not False or not True)  # Warning: this code will never run
+    printf("%d", not False or not False)  # Warning: this code will never run
     printf("\n")
 
     # Output: Side effects and aAbBcd

tests/should_succeed/unreachable_warning.jou

@@ -39,7 +39,12 @@ def lots_of_unreachable_code() -> None:
         puts("blah")
         i = i+1
 
+def with_not() -> None:
+    if not True:
+        puts("Hello")  # Warning: this code will never run
+
 def main() -> int:
     after_return()
+    with_not()
     # Can't run infinite loops (test script redirects output to file)
     return 0