Re: [PATCH 1/2] Using pli(paddi) and rotate to build 64bit constants

[Jiufu Guo <guojiufu@linux.ibm.com>]

Segher Boessenkool <segher@kernel.crashing.org> writes:

> On Mon, Sep 05, 2022 at 02:25:29PM +0800, Jiufu Guo wrote:
>> > On Fri, Sep 02, 2022 at 02:56:21PM +0800, Jiufu Guo wrote:
>> > Or force the testcase to use r0 some other way.  Well, "forcing" cannot
>> > be done, but we can probably encourage it (via a local register asm for
>> > example, or by tying the var to the output of an asm that is hard reg 0,
>> > or perhaps there are other ways as well :-) )
>> Specify register is very helpful here! Both below two cases could help
>> register 0 to be selected for a variable.  Great!  Thanks!
>
>> >> The reason of using "(?n)^\s+[a-z]" is to keep this test case pass no
>> >> matter the splitter running before or after RA.
>> >
>> > Ah.  Some short comment in the testcase please?
>> Thanks.  We can check individual instructions to check better asm
>> pli+pli+rldimi is generated, since the splitter could run in split1 pass.
>
> It's always a tradeoff: if we scan for too specific code the testcase
> will need a lot of maintenance, and that does not scale.  If on the
> other hand we do test less than we really want, well, that is less than
> we really want to test :-)
Yes :)
>
> The changes / additions we agreed to are preapproved btw.  But please
> post the thing you eventually commit to the mailing list :-)
Sure! I updated the patch for testcases and also for code part; I would
submit for review before commit again for new comments. :)

The updated patch is as:
https://gcc.gnu.org/pipermail/gcc-patches/2022-September/601150.html

Thanks again!


BR,
Jeff(Jiufu)

>
>
> Segher