https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87009
--- Comment #1 from MCCCS <mcccs at gmx dot com> ---
Proposed patch:
Index: gcc/match.pd
===================================================================
--- gcc/match.pd (revision 263646)
+++ gcc/match.pd (working copy)
@@ -776,6 +776,11 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
(bit_not (bit_and:cs (bit_not @0) @1))
(bit_ior @0 (bit_not @1)))
+/* ~(~a | b) --> a & ~b */
+(simplify
+ (bit_not (bit_ior:cs (bit_not @0) @1))
+ (bit_and @0 (bit_not @1)))
+
/* Simplify (~X & Y) to X ^ Y if we know that (X & ~Y) is 0. */
#if GIMPLE
(simplify
Index: gcc/testsuite/g++.dg/pr87009.C
===================================================================
--- gcc/testsuite/g++.dg/pr87009.C (nonexistent)
+++ gcc/testsuite/g++.dg/pr87009.C (working copy)
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-original" } */
+/* { dg-final { scan-tree-dump-times " ^ " 3 "original" } */
+
+int f1 (int x, int s)
+{
+ return ~(~(x|s)|x)|~(~(x|s)|s);
+}
+
+int f2 (int x, int s)
+{
+ return ~(~(~x&s)&~(x&~s));
+}
+
+int f3 (int x, int s)
+{
+ return ~((x|~s)&(~x|s));
+}
