On Mon, Jul 13, 2020 at 4:50 PM Roger Sayle <ro...@nextmovesoftware.com> wrote: > > > Hi Richard, > > > It seems to be improving TARGET_TRULY_NOOP_TRUNCATION documentation might > > be useful here. > > This is an excellent suggestion. How about the following/attached: > > 2020-07-13 Roger Sayle <ro...@nextmovesoftware.com> > > gcc/ChangeLog: > * doc/tm.texi (TARGET_TRULY_NOOP_TRUNCATION): Clarify that targets > that (sometimes) return false, indicating SUBREGs shouldn't be > used, also need to provide a trunc?i?i2 optab that performs this > truncation. > > > The only user (after your patch) of this hook is in function.c for the > > function parameter setup btw. > > The targetm.truly_noop_truncation in assign_parm_setup_block is the last > place that calls this > hook directly (with sizes), but the majority of uses go via > TRULY_NOOP_TRUNCATION_MODES_P > as defined in machmode.h. > > I'll prepare a patch to switch function.c to use TRULY_NOOP_TRUNCATION_MODE_P > so that we > are consistent throughout the compiler. In theory, this hook could then be > changed to take modes > instead of (poly_unit64) sizes, but that clean-up might be tricky without > access to the affected > platforms. > > The hard register semantics that you're referring to are related to > TARGET_MODES_TIEABLE_P, > which is documented to have interesting interactions with > TARGET_TRULY_NOOP_TRUNCATION. > > Is the above documentation change Ok for mainline?
OK. Thanks, Richard. > Thanks, > Roger > -- >
