[Bug middle-end/82062] [8 regression] simple conditional expressions no longer folded

[ebotcazou at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82062

--- Comment #7 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
But in fact we probably just need:

Index: fold-const.c
===================================================================
--- fold-const.c        (revision 254037)
+++ fold-const.c        (working copy)
@@ -3366,7 +3366,8 @@ operand_equal_p (const_tree arg0, const_
 #undef OP_SAME_WITH_NULL
 }


-/* Similar to operand_equal_p, but strip nops first.  */
+/* Similar to operand_equal_p, but see if ARG1 might be a variant of ARG0
+   with a different signedness or a simple conversion.  */

 static bool
 operand_equal_for_comparison_p (tree arg0, tree arg1)
@@ -3378,12 +3379,15 @@ operand_equal_for_comparison_p (tree arg
       || ! INTEGRAL_TYPE_P (TREE_TYPE (arg1)))
     return false;

-  /* Discard any conversions that don't change the modes of ARG0 and ARG1
-     and see if the inner values are the same.  This removes any
-     signedness comparison, which doesn't matter here.  */
-  STRIP_NOPS (arg0);
-  STRIP_NOPS (arg1);
-  if (operand_equal_p (arg0, arg1, 0))
+  tree op0 = arg0;
+  tree op1 = arg1;
+  STRIP_NOPS (op0);
+  STRIP_NOPS (op1);
+  if (operand_equal_p (op0, op1, 0))
+    return true;
+
+  if (TREE_CODE (arg1) == NOP_EXPR
+      && operand_equal_p (arg0, TREE_OPERAND (arg1, 0), 0))
     return true;

   return false;