[Bug ipa/82808] [7/8 Regression] LTO clone wrong value

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82808

--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
ipa_get_jf_pass_through_result has multiple issues:

static tree
ipa_get_jf_pass_through_result (struct ipa_jump_func *jfunc, tree input)
{
  tree restype, res;

  if (ipa_get_jf_pass_through_operation (jfunc) == NOP_EXPR)
    return input;

we may miss a truncation here (and should check for CONVERT_EXPR_CODE_P).

  if (!is_gimple_ip_invariant (input))
    return NULL_TREE;

  if (TREE_CODE_CLASS (ipa_get_jf_pass_through_operation (jfunc))
      == tcc_unary)
    res = fold_unary (ipa_get_jf_pass_through_operation (jfunc),
                      TREE_TYPE (input), input);

the bug here is that the operation is type-changing but we use the
type of the input(!) rather than the type of the output when computing
the result.  I suppose the output is the type of the current formal
parameter -- is that available somehow?

  else
    {
      if (TREE_CODE_CLASS (ipa_get_jf_pass_through_operation (jfunc))
          == tcc_comparison)
        restype = boolean_type_node;
      else
        restype = TREE_TYPE (input);

same issue for operations like widen_sum_expr but of course less likely
to hit us here.

      res = fold_binary (ipa_get_jf_pass_through_operation (jfunc), restype,
                         input, ipa_get_jf_pass_through_operand (jfunc));
    }
  if (res && !is_gimple_ip_invariant (res))
    return NULL_TREE;


I think the immediate thing to do is make the list of handled expression
codes explicit - thus change the tree-code-class checks to

switch (code)
 {
 case handled-unary:
  fold_unary...

 case handled-comparison:
  ...

 etc.

or somehow properly get the jf "target" type.