Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
kconfig: add comments to expression transformations
Provide explanations for complex transformations.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
+37
-6
+37
-6
scripts/kconfig/expr.c
+37
-6
scripts/kconfig/expr.c
···
442
442
}
443
443
}
444
444
if (sym1->type == S_BOOLEAN) {
445
+
// a || !a -> y
445
446
if ((e1->type == E_NOT && e1->left.expr->type == E_SYMBOL && e2->type == E_SYMBOL) ||
446
447
(e2->type == E_NOT && e2->left.expr->type == E_SYMBOL && e1->type == E_SYMBOL))
447
448
return expr_alloc_symbol(&symbol_yes);
···
648
647
* Performs various simplifications involving logical operators and
649
648
* comparisons.
650
649
*
650
+
* For bool type:
651
+
* A=n -> !A
652
+
* A=m -> n
653
+
* A=y -> A
654
+
* A!=n -> A
655
+
* A!=m -> y
656
+
* A!=y -> !A
657
+
*
658
+
* For any type:
659
+
* !!A -> A
660
+
* !(A=B) -> A!=B
661
+
* !(A!=B) -> A=B
662
+
* !(A<=B) -> A>B
663
+
* !(A>=B) -> A<B
664
+
* !(A<B) -> A>=B
665
+
* !(A>B) -> A<=B
666
+
* !(A || B) -> !A && !B
667
+
* !(A && B) -> !A || !B
668
+
*
669
+
* For constant:
670
+
* !y -> n
671
+
* !m -> m
672
+
* !n -> y
673
+
*
651
674
* Allocates and returns a new expression.
652
675
*/
653
676
struct expr *expr_transform(struct expr *e)
···
699
674
if (e->left.sym->type != S_BOOLEAN)
700
675
break;
701
676
if (e->right.sym == &symbol_no) {
677
+
// A=n -> !A
702
678
e->type = E_NOT;
703
679
e->left.expr = expr_alloc_symbol(e->left.sym);
704
680
e->right.sym = NULL;
705
681
break;
706
682
}
707
683
if (e->right.sym == &symbol_mod) {
684
+
// A=m -> n
708
685
printf("boolean symbol %s tested for 'm'? test forced to 'n'\n", e->left.sym->name);
709
686
e->type = E_SYMBOL;
710
687
e->left.sym = &symbol_no;
···
714
687
break;
715
688
}
716
689
if (e->right.sym == &symbol_yes) {
690
+
// A=y -> A
717
691
e->type = E_SYMBOL;
718
692
e->right.sym = NULL;
719
693
break;
···
724
696
if (e->left.sym->type != S_BOOLEAN)
725
697
break;
726
698
if (e->right.sym == &symbol_no) {
699
+
// A!=n -> A
727
700
e->type = E_SYMBOL;
728
701
e->right.sym = NULL;
729
702
break;
730
703
}
731
704
if (e->right.sym == &symbol_mod) {
705
+
// A!=m -> y
732
706
printf("boolean symbol %s tested for 'm'? test forced to 'y'\n", e->left.sym->name);
733
707
e->type = E_SYMBOL;
734
708
e->left.sym = &symbol_yes;
···
738
708
break;
739
709
}
740
710
if (e->right.sym == &symbol_yes) {
711
+
// A!=y -> !A
741
712
e->type = E_NOT;
742
713
e->left.expr = expr_alloc_symbol(e->left.sym);
743
714
e->right.sym = NULL;
···
748
717
case E_NOT:
749
718
switch (e->left.expr->type) {
750
719
case E_NOT:
751
-
// !!a -> a
720
+
// !!A -> A
752
721
tmp = e->left.expr->left.expr;
753
722
free(e->left.expr);
754
723
free(e);
···
757
726
break;
758
727
case E_EQUAL:
759
728
case E_UNEQUAL:
760
-
// !a='x' -> a!='x'
729
+
// !(A=B) -> A!=B
761
730
tmp = e->left.expr;
762
731
free(e);
763
732
e = tmp;
···
765
734
break;
766
735
case E_LEQ:
767
736
case E_GEQ:
768
-
// !a<='x' -> a>'x'
737
+
// !(A<=B) -> A>B
769
738
tmp = e->left.expr;
770
739
free(e);
771
740
e = tmp;
···
773
742
break;
774
743
case E_LTH:
775
744
case E_GTH:
776
-
// !a<'x' -> a>='x'
745
+
// !(A<B) -> A>=B
777
746
tmp = e->left.expr;
778
747
free(e);
779
748
e = tmp;
780
749
e->type = e->type == E_LTH ? E_GEQ : E_LEQ;
781
750
break;
782
751
case E_OR:
783
-
// !(a || b) -> !a && !b
752
+
// !(A || B) -> !A && !B
784
753
tmp = e->left.expr;
785
754
e->type = E_AND;
786
755
e->right.expr = expr_alloc_one(E_NOT, tmp->right.expr);
···
789
758
e = expr_transform(e);
790
759
break;
791
760
case E_AND:
792
-
// !(a && b) -> !a || !b
761
+
// !(A && B) -> !A || !B
793
762
tmp = e->left.expr;
794
763
e->type = E_OR;
795
764
e->right.expr = expr_alloc_one(E_NOT, tmp->right.expr);