Re: [PATCH] vect: Don't allow vect_emulated_vector_p type in vectorizable_call [PR106322]

["Kewen.Lin" <linkw@linux.ibm.com>]

on 2022/8/12 19:14, Richard Biener wrote:
> On Fri, Aug 12, 2022 at 11:41 AM Kewen.Lin <linkw@linux.ibm.com> wrote:
>>
>> Hi,
>>
>> As PR106322 shows, in some cases for some vector type whose
>> TYPE_MODE is a scalar integral mode instead of a vector mode,
>> it's possible to obtain wrong target support information when
>> querying with the scalar integral mode.  For example, for the
>> test case in PR106322, on ppc64 32bit vectorizer gets vector
>> type "vector(2) short unsigned int" for scalar type "short
>> unsigned int", its mode is SImode instead of V2HImode.  The
>> target support querying checks umul_highpart optab with SImode
>> and considers it's supported, then vectorizer further generates
>> .MULH IFN call for that vector type.  Unfortunately it's wrong
>> to use SImode support for that vector type multiply highpart
>> here.
>>
>> This patch is to teach vectorizable_call analysis not to allow
>> vect_emulated_vector_p type for both vectype_in and vectype_out
>> as Richi suggested.
>>
>> Bootstrapped and regtested on x86_64-redhat-linux,
>> aarch64-linux-gnu and powerpc64{,le}-linux-gnu.
>>
>> Is it ok for trunk?
> 
> OK for trunk.
> 
>> If it's ok, I guess we want this to be
>> backported?
> 
> Yes, but you just missed the RC for 12.2 so please wait until after GCC 12.2
> is released and the branch is open again.  The testcase looks mightly
> complicated
> so fallout there might be well possible as well ;)  I suppose it wasn't possible
> to craft a simple C testcase after the analysis?

Thanks for the hints!  Let me give it a try next week and get back to you then.

BR,
Kewen