Re: [avr-llvm-devel] Inline assembly.

[Borja F. <bor...@gm...>]

1) I agree.
3) What happens when you use multibyte constraints with "e" or "b".
4) Hah ok, btw no need to check for i64?


2013/7/24 Stepan Dyatkovskiy <stp...@na...>

> Hi Borja,
>
>
> > 1) You implemented the "aN" constraint by also allowing b,c,d
> > constraints. I'm not sure if gcc implements this, my guess is that only
> > "a" is needed. Please check to see what gcc does here.
>
> For b,c,d avr-gcc acts like it meet %a. I think its wrong and untested
> behaviour, so I just restricted usage to single 'a' character.
>
>
> > 2) Make getAlternativeRegName return a char instead of a string since we
> > only need to return one letter.
>
> Done
>
>
> > 3) Related to the changes in AVRISelLowering.cpp, do we need to care
> > about more register constraints apart of the ones you already covered?
>
> What you mean? I think all constraints are covered now. If no, we can find
> out it during compilation (avr-libc, arduino, etc).
>
>
> > 4) Now that wider types have been covered, please check if the assert I
> > commented out in AVRISelLowering.cpp in the inline asm code can be
> > removed or what.
>
> I replaced this assertion with error message. Suppose its better than
> killing the compiler :-)
>
> New patch is attached.
>
> -Stepan.
>
>
> Borja Ferrer wrote:
>
>> Hello Stepan,
>> The patch looks good, but I have some questions/comments:
>>
>> 1) You implemented the "aN" constraint by also allowing b,c,d
>> constraints. I'm not sure if gcc implements this, my guess is that only
>> "a" is needed. Please check to see what gcc does here.
>> 2) Make getAlternativeRegName return a char instead of a string since we
>> only need to return one letter.
>> 3) Related to the changes in AVRISelLowering.cpp, do we need to care
>> about more register constraints apart of the ones you already covered?
>> 4) Now that wider types have been covered, please check if the assert I
>> commented out in AVRISelLowering.cpp in the inline asm code can be
>> removed or what.
>>
>>
>>
>> 2013/7/24 Stepan Dyatkovskiy <stp...@na... <mailto:stp...@na...
>> >>
>>
>>
>>     Hello Borja,
>>     Here is the new patch for multibyte reference. Please look at new
>>     tests to see what was implemented exactly.
>>     To fix issue I described in previous letter I've added new reg
>>     classes that contains pairs of 8 bit registers:
>>     If we pass i32 parameter that should be split onto four 8 bit regs,
>>     we set i16 register class first, then it would be replaced with 8
>>     bit registers if needed. Currently I see it is the only solution
>>     that doesn't touch vmcore.
>>
>>     -Stepan.
>>
>>     Stepan Dyatkovskiy wrote:
>>
>>         Hello Borja,
>>         Great. I have found out next inline-asm issue.
>>         When you pass i32 bit type, it could be split onto two registers
>>         only,
>>         no matter which register class you set for it. This behaviour is
>>         implemented in SelectionDAGBuilder::__**visitInlineAsm. I think
>> I'll
>>
>>         implement simplest version of ExpandInlineAsm today, that will fix
>>         operand types properly.
>>
>>         -Stepan
>>
>>         Borja Ferrer wrote:
>>
>>             I've been adding fixes to pass a ton of regression in the
>>             Generic folder.
>>             Currently there are two tests that fail with a "cannot select
>>             build_pair" related to adding 16bit reg classes in the
>>             inline asm code.
>>             The rest of failing tests are related with not being able to
>>             run llc
>>             with -O0. There's a serious codegen bug that i spotted
>>             yesterday while
>>             doing the fixes that I need to work on.
>>
>>
>>             2013/7/22 Borja Ferrer <bor...@gm...
>>             <mailto:bor...@gm...>
>>             <mailto:bor...@gm... <mailto:bor...@gm...>*
>> *>__>
>>
>>                   Hello Stepan,
>>
>>                   3) Yes, it's the second case. It's explained in
>>             http://www.nongnu.org/avr-__**libc/user-manual/inline_asm.__*
>> *html <http://www.nongnu.org/avr-__libc/user-manual/inline_asm.__html>
>>
>>             <http://www.nongnu.org/avr-**libc/user-manual/inline_asm.**
>> html <http://www.nongnu.org/avr-libc/user-manual/inline_asm.html>>
>>                   but in case there are any doubts basically it works
>>             the same way as
>>                   multibyte constraints except that when you see an
>>             "aN", where N is a
>>                   number, you should print the alternative regname. Of
>>             course this
>>                   should only work for X Y and Z, not sure how gcc
>>             complains when you
>>                   use another register, or maybe it ignores it and
>>             prints the normal
>>                   register name.
>>
>>
>>
>>
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