Ian Lance Taylor wrote:
> Kenneth Zadeck <zad...@naturalbridge.com> writes:
>
>> Would those that know, (or even those that are just generally vocal) be
>> willing to support a change rtl.texi for sign_extract (and by
>> implication, zero_extract) from
>>
>> If @var{loc} is in memory, its mode must be a single-byte integer mode.
>> If @var{loc} is in a register, the mode to use is specified by the
>> operand of the @code{insv} or @code{extv} pattern
>> (@pxref{Standard Names}) and is usually a full-word integer mode,
>> which is the default if none is specified.
>>
>> to a version that explicitly prohibits the use of a mode longer than a word?
>>
>> The back ends do not appear to support this anyway.
>
> I guess the obvious counterexample would be a processor which supported
> vector registers and supported bitfield operations on such registers. I
> don't know of any such processors. The restriction would probably be
> fine in practice, but why do you want to make it?
No, actually the question I asked Kenny was not about modes wider than a
word, but about hard registers spanning more than one hard registers.
That would be something like
(set (reg:SI 0) (zero_extract:SI (reg:DI 2)
(const_int 32) (const_int 16)))
with word_mode == SImode. Currently DF would mishandle this; Kenny
thought the doc should be changed if this is actually unsupported.
Paolo
