Re: [PATCH v2] DSE: Bugfix ICE after allow vector type in get_stored_val

[Jeff Law]

On 2/27/24 21:51, Li, Pan2 wrote:
   if (!targetm.modes_tieable_p (src_int_mode, src_mode))
     return NULL_RTX;
   if (!targetm.modes_tieable_p (int_mode, mode))
     return NULL_RTX;

Yes, will return NULL_RTX for in the first if, given src_int_mode is E_DImode 
while src_mode is
E_V2SFmode and mode is E_V4QImode. The extract_low_bits convert the modes 
E_V2SFmode/E_V4QImode
to E_DImode/E_SImode in advance before tieable checking, validate_subreg and 
gen_lowpart.

Not sure if my understanding is correct but looks extract_low_bits cannot take 
care of vector modes
up to a point because vector modes are always untieable to its' int mode, and 
then return NULL_RTX.
Well, the code tries to turn the vector mode into a suitable integer 
mode via int_mode_for_mode.  That takes a mode, including vector modes 
and tries to find an integer mode of the exact same size.

So it's going to check if V2SF can be tied to DI and V4QI with SI.  I 
suspect those are going to fail for RISC-V as those aren't tieable.

Jeff