[Bug tree-optimization/93265] memcmp comparisons of structs wrapping a primitive type not as compact/efficient as direct comparisons of the underlying primitive type under -Os

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93265

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2020-01-14
          Component|c                           |tree-optimization
     Ever confirmed|0                           |1

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
So I see it already resolved to a direct compare during GENERIC folding
which is probably confused by the COMPOUND_LITERAL_EXPR:

  return memcmp ((const void *) &X, (const void *) &<<< Unknown tree:
compound_literal_expr
    const struct a_tp D.2112 = {.x=42}; >>>, 4) == 0;

I think tree-ssa-strlen.c has code to change memcmp to memcmp_eq which can
be more optimally expanded.  It also has code to directly emit more optimal
GIMPLE.

Not sure why that doesn't fire here.  Confirmed.