Question about make_extraction() in combine.c

[Segher Boessenkool]

Hi!

On Wed, Nov 14, 2018 at 11:22:58AM -0800, Michael Eager wrote:
> The (mem:SI) is converted to (mem:QI).
> 
> The return from make_extract() is
>    (zero_extract:SI (mem:QI (reg/v/f:SI 50 [ gp ]))
>       (const_int 1 [0x1])
>       (const_int 2 [0x2]))
> 
> The target has an instruction pattern for zero_extract, but it matches
> SI values, not QI.  So the instruction which implements a test of a bit
> flag is never generated.

The RTL documentation says:

  If @var{loc} is in memory, its mode must be a single-byte integer mode.

But obviously various ports use other modes, too.  I wonder if that ever
worked well.


Segher