Validity of SUBREG+AND-imm transformations

[Richard Henderson]

On 03/07/2016 02:49 PM, Jeff Law wrote:
> On 03/07/2016 03:44 AM, Kyrill Tkachov wrote:
>>>
>>
>> The RTL documentation for ASHIFT and friends says that the shift amount
>> must be:
>> "a fixed-point mode or be a constant with mode @code{VOIDmode}; which
>> mode is determined by the mode called for in the machine description
>> entry for the left-shift instruction". For example, on the VAX, the mode
>> of @var{c} is @code{QImode} regardless of @var{m}.
> Use QImode in the named pattern/expander and use the other modes in an
> unnamed/anonymous pattern.

I thought the same thing you did.  But I tried it out on the aarch64 port and 
it didn't work.  Combine kept coming back to the QImode pattern.

I didn't want to look into it any farther than that, lest I fall down a rabbit 
hole, but there's more to it than just tweaking the patterns.


r~