On Thu, 15 Sep 2016, Wilco Dijkstra wrote: > Yes, if there are targets which don't implement TImode operations then > surely they should be automatically split into DImode operations before > or during Expand?
The operations generally don't exist if the mode fails the scalar_mode_supported_p hook. I don't know whether there are sufficient TImode operations for the bitwise operations you need here, even in the case where it fails that hook (and so you can't declare variables with that mode) - it's arithmetic, and the ABI support needed for argument passing, that are harder to do by splitting into smaller modes (and that GCC generally only handles in libgcc for 2-word operands, not for 4-word operands). > So for now it would seem best to keep the boolean false for quad formats > on 32-bit targets. This is a function of command-line options, not the format, so it can't go in the table. The table should describe the format properties only. Does the expansion work, in fact, for __float128 on 32-bit x86, given the boolean set to true (other relevant cases include 128-bit long double on 32-bit s390 and 32-bit sparc with appropriate options to make long double 128-bit)? If it does, it may be OK to use modes that fail the scalar_mode_supported_p hook. If something doesn't work in that case, the right way to avoid an expansion is not to set the boolean to false in the table of formats, it's to loop over supported integer modes seeing if there is one wide enough that also passes the scalar_mode_supported_p hook. -- Joseph S. Myers jos...@codesourcery.com
