tree.cc: Use useless_type_conversion_p in tree_builtin_call_types_compatible_p while...

tree.cc: Use useless_type_conversion_p in tree_builtin_call_types_compatible_p while in gimple form [PR105253]

tree_builtin_call_types_compatible_p uses TYPE_MAIN_VARIANT comparisons
or tree_nop_conversion_p to ensure a builtin has correct GENERIC arguments.
Unfortunately this regressed when get_call_combined_fn is called during
GIMPLE optimizations.  E.g. when number_of_iterations_popcount is called,
it doesn't ensure TYPE_MAIN_VARIABLE compatible argument type, it picks
__builtin_popcount{,l,ll} based just on types' precision and doesn't
fold_convert the arg to the right type.  We are in GIMPLE, such conversions
are useless...
So, either we'd need to fix number_of_iterations_popcount to add casts
and inspect anything else that creates CALL_EXPRs late, or we can
in tree_builtin_call_types_compatible_p just use the GIMPLE type
comparisons (useless_type_conversion_p) when we are in GIMPLE form and
the TYPE_MAIN_VARIANT comparison or tree_nop_conversion_p test otherwise.

I think especially this late in stage4 the latter seems safer to me.

2022-04-13  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/105253
	* tree.cc (tree_builtin_call_types_compatible_p): If PROP_gimple,
	use useless_type_conversion_p checks instead of TYPE_MAIN_VARIANT
	comparisons or tree_nop_conversion_p checks.

	* gcc.target/i386/pr105253.c: New test.