[trunk] Addition to subreg section of rtl.text.

[Kenneth Zadeck]

Ian Lance Taylor wrote:
> Richard Sandiford <rsandifo@nildram.co.uk> writes:
>
>   
>>>  The other use of @code{subreg} is to extract the individual registers of
>>>  a multi-register value.  Machine modes such as @code{DImode} and
>>>  @code{TImode} can indicate values longer than a word, values which
>>>  usually require two or more consecutive registers.  To access one of the
>>>  registers, use a @code{subreg} with mode @code{SImode} and a
>>> -@var{bytenum} offset that says which register.
>>> +@var{bytenum} offset that says which register.  In this case, the
>>> +@var(bytenum) must align the outer value to a word boundary if the inner
>>>       
>>        ^^^^^^^^^
>> Nit: {bytenum}
>>
>>     
>>> +register is a psuedo or to a register boundary if the inner register is
>>> +a hard register.  
>>>       
>> As I understand it, this is only true if the _outer_ register is
>> word-sized or bigger.  You can have (subreg:QI (reg:DI ...) 3) on
>> a 32-bit big-endian target, for example.
>>     
>
> True in general, but that is not the specific case addressed in this
> paragraph, that of extracting the individual registers of a
> multi-register value.  But perhaps this could be made more clear.
>
> Ian
>   
I changed the "In this case" to "In this multi-register case" and fixed
richards nit.
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