Re: Re: [PATCH] RISC-V: Fix RVV testcases.

[Palmer Dabbelt <palmer@dabbelt.com>]

On Mon, 31 Oct 2022 16:52:25 PDT (-0700), juzhe.zhong@rivai.ai wrote:
> These cases actually doesn't care about -mabi, they just need 'v' in -march.
> Can you tell me how to fix these testcases for "fails on targets without ilp32d" ?
> These failures are bogus failures since if you specify -mabi=ilp32d when you are using GNU toolchain which is build up with "--arch=ilp32" let say.
> It will fail. Report there is no "ilp32d". So I fix these testcase by replacing "ilp32d" into "ilp32".

So the problem is this just moves the failures around, rather than 
failing on toolchains that lack ilp32d support it'll fail on toolchains 
that lack ilp32 support.  The ABI naming scheme sort of makes them look 
like extensions, but they're just incompatible with each other.

I can see a handful of ways to fix this:

* Add some sort of automatic ABI scheme to GCC.  LLVM already does this 
  and there was a GCC patch for it that had some issues, but IMO having 
  something like -mabi=auto-{min,max} would be useful as users keep 
  running into this problem.  We could also add something to DejaGNU 
  that does this.
* Add some sort of -march=+v to GCC, along the lines of the .option 
  arch,+v stuff in assembly but from the command line.  I seem to 
  remember proposals for that floating around somewhere, but can't find 
  anything.  This could probably also to DejaGNU.
* Decorate all these V functions with the +arch attributes.  That 
  wouldn't require any compiler changes, but it's kind of clunky.
* Add some sort of test suite logic (maybe in DejaGNU?) to check and see 
  if the desired ABI is linkable before attempting to do so.  That might 
  be generically useful.

> Thank you.
> 
> 
> 
> juzhe.zhong@rivai.ai
>  
> From: Palmer Dabbelt
> Date: 2022-11-01 06:30
> To: gcc-patches
> CC: juzhe.zhong; gcc-patches; schwab; Kito Cheng
> Subject: Re: [PATCH] RISC-V: Fix RVV testcases.
> On Mon, 31 Oct 2022 15:00:49 PDT (-0700), gcc-patches@gcc.gnu.org wrote:
>>
>> On 10/30/22 19:40, juzhe.zhong@rivai.ai wrote:
>>> From: Ju-Zhe Zhong <juzhe.zhong@rivai.ai>
>>>
>>> gcc/testsuite/ChangeLog:
>>>
>>>          * gcc.target/riscv/rvv/base/abi-2.c: Change ilp32d to ilp32.
>>>          * gcc.target/riscv/rvv/base/abi-3.c: Ditto.
>>>          * gcc.target/riscv/rvv/base/abi-4.c: Ditto.
>>>          * gcc.target/riscv/rvv/base/abi-5.c: Ditto.
>>>          * gcc.target/riscv/rvv/base/abi-6.c: Ditto.
>>>          * gcc.target/riscv/rvv/base/abi-7.c: Ditto.
>>>          * gcc.target/riscv/rvv/base/mov-1.c: Ditto.
>>>          * gcc.target/riscv/rvv/base/mov-10.c: Ditto.
>>>          * gcc.target/riscv/rvv/base/mov-11.c: Ditto.
>>>          * gcc.target/riscv/rvv/base/mov-12.c: Ditto.
>>>          * gcc.target/riscv/rvv/base/mov-13.c: Ditto.
>>>          * gcc.target/riscv/rvv/base/mov-2.c: Ditto.
>>>          * gcc.target/riscv/rvv/base/mov-3.c: Ditto.
>>>          * gcc.target/riscv/rvv/base/mov-4.c: Ditto.
>>>          * gcc.target/riscv/rvv/base/mov-5.c: Ditto.
>>>          * gcc.target/riscv/rvv/base/mov-6.c: Ditto.
>>>          * gcc.target/riscv/rvv/base/mov-7.c: Ditto.
>>>          * gcc.target/riscv/rvv/base/mov-8.c: Ditto.
>>>          * gcc.target/riscv/rvv/base/mov-9.c: Ditto.
>>>          * gcc.target/riscv/rvv/base/pragma-1.c: Ditto.
>>>          * gcc.target/riscv/rvv/base/user-1.c: Ditto.
>>>          * gcc.target/riscv/rvv/base/user-2.c: Ditto.
>>>          * gcc.target/riscv/rvv/base/user-3.c: Ditto.
>>>          * gcc.target/riscv/rvv/base/user-4.c: Ditto.
>>>          * gcc.target/riscv/rvv/base/user-5.c: Ditto.
>>>          * gcc.target/riscv/rvv/base/user-6.c: Ditto.
>>>          * gcc.target/riscv/rvv/base/vsetvl-1.c: Ditto.
>>
>> I'm pretty new to the RISC-V world, but don't some of the cases
>> (particularly the abi-* tests) verify that the ABI specification does
>> not override the arch specification WRT availability of types?
>  
> I think that depends on what the ABI specification says here, as it 
> could really go many ways.  Most of the RISC-V targets just use -mabi to 
> control how arguments end up passed in functions, not the availability 
> of types.  I can't find the ABI spec for these, though, so I'm not 
> entirely sure how they're supposed to work...
>  
> That said, I'm not sure why we need any of these -mabi changes?  Just 
> from spot checking some of the examples it doesn't look like there 
> should be any functional difference between ilp32 and ilp32d here: 
> -march is always specified so ilp32d looks valid.  If this is just to 
> fix the "fails on targets without ilp32d" [1], then IMO it's not really 
> a fix: we're essentially just changing that to "fails on targets without 
> ilp32", we either need some sort of automatic march/mabi setting or a 
> dependency on the availiable multilibs.  Some of these can probably 
> avoid linking, but we'll have execution tests at some point.
>  
> 1: https://gcc.gnu.org/pipermail/gcc-patches/2022-October/604644.html
>