Jozef Lawrynowicz <joze...@mittosystems.com> writes:
> In d8487c949ad5 (~GCC 4.9.0), MODE_PARTIAL_INT modes were changed from
> having an unknown number of undefined bits, to having a known number of
> undefined bits, however the documentation on using SUBREG expressions
> with MODE_PARTIAL_INT modes was not updated to reflect this.
>
> The attached patch updates that portion of the GCC internals
> documentation.
>
> Ok for trunk?
Thanks for doing this. OK for trunk with one very minor nit:
> -does not guarantee that @samp{(subreg:HI (reg:PSI 0) 0)} has the
> -value @samp{(reg:HI 4)}.
> +sets the low 16 bits of @samp{(reg:PSI 0)} to @samp{(reg:HI 4)}, and
> +the high 4 defined bits of @samp{(reg:PSI 0)} retain their
> +original value. The behavior here is therefore the same as
IMO reads more naturally as “the same as for”.
Richard
> +normal @code{subreg}s, when there are no
> +@code{MODE_PARTIAL_INT} modes involved.
>
> @cindex @code{TARGET_CAN_CHANGE_MODE_CLASS} and subreg semantics
> The rules above apply to both pseudo @var{reg}s and hard @var{reg}s.
