https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126689
--- Comment #4 from Drea Pinski <pinskia at gcc dot gnu.org> ---
Looks like it is already handled in backprop:
backprop::process_builtin_call_use:
CASE_CFN_COPYSIGN:
CASE_CFN_COPYSIGN_FN:
/* The sign of the first input is ignored. */
if (rhs != gimple_call_arg (call, 1))
info->flags.ignore_sign = true;
break;
strip_sign_op_1:
else if (gcall *call = dyn_cast <gcall *> (def_stmt))
switch (gimple_call_combined_fn (call))
{
CASE_CFN_COPYSIGN:
CASE_CFN_COPYSIGN_FN:
return gimple_call_arg (call, 0);
default:
break;
}
Oh but this is a different this is about second operand.
We have a pattern for the first argument one too:
```
/* copysign(copysign(x, y), z) -> copysign(x, z). */
(for copysigns (COPYSIGN_ALL)
(simplify
(copysigns (copysigns @0 @1) @2)
(copysigns @0 @2)))
```
