[Bug rtl-optimization/78546] [6/7 Regression] wrong code at -O2 and above

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78546

--- Comment #9 from Richard Biener <rguenth at gcc dot gnu.org> ---
Testing

diff --git a/gcc/match.pd b/gcc/match.pd
index 2d4e019..9e5df64 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -1216,6 +1216,13 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
      (if (cst && !TREE_OVERFLOW (cst))
       (minus { cst; } @0)))))

+  /* CST - (CST - A) -> CST - A  */
+  (simplify
+   (minus CONSTANT_CLASS_P@1 (minus CONSTANT_CLASS_P@2 @0))
+   (with { tree cst = const_binop (MINUS_EXPR, type, @1, @2); }
+    (if (cst && !TREE_OVERFLOW (cst))
+     (minus { cst; } @0))))
+
   /* ~A + A -> -1 */
   (simplify
    (plus:c (bit_not @0) @0)

for the optimization regression.