[Bug target/113240] New: Use wrong rule to pass fixed-length(size<=2*XLEN) vector argument

[Bug target/113240] New: Use wrong rule to pass fixed-length(size<=2*XLEN) vector argument

[lehua.ding at rivai dot ai]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113240

            Bug ID: 113240
           Summary: Use wrong rule to pass fixed-length(size<=2*XLEN)
                    vector argument
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: lehua.ding at rivai dot ai
  Target Milestone: ---

According to a recent proposal
(https://github.com/riscv-non-isa/riscv-elf-psabi-doc/pull/416), GCC
incorrectly uses references when passing fixed-length vector arguments with
size less than or equal to 2*VLEN instead of scalar registers for passing.
Reproduced online: https://godbolt.org/z/3ooovcz7c

C Code:
```
#include <stdint.h>

typedef int v4si __attribute__ ((vector_size (16)));

v4si foo (v4si a, v4si b)
{
  v4si c = a + b;
  return c;
}
```

Asm:
```
foo:
        vsetivli        zero,4,e32,m1,ta,ma
        vle32.v v1,0(a1)
        vle32.v v2,0(a2)
        vadd.vv v1,v1,v2
        vse32.v v1,0(a0)
        ret
```

[Bug target/113240] Use wrong rule to pass fixed-length(size<=2*XLEN) vector argument

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113240

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
There needs to be a -Wabi warning for this too for the change between versions.

[Bug target/113240] Use wrong rule to pass fixed-length(size<=2*XLEN) vector argument

[lehua.ding at rivai dot ai]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113240

--- Comment #2 from Lehua Ding <lehua.ding at rivai dot ai> ---
(In reply to Andrew Pinski from comment #1)
> There needs to be a -Wabi warning for this too for the change between
> versions.

I'm more inclined to think of it as a bug, since the vector ABI specification
is still being worked out and isn't stable and currently used with vector
arguments will throw a warning about unstable.

[Bug target/113240] Use wrong rule to pass fixed-length(size<=2*XLEN) vector argument

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113240

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Lehua Ding from comment #2)
> (In reply to Andrew Pinski from comment #1)
> > There needs to be a -Wabi warning for this too for the change between
> > versions.
> 
> I'm more inclined to think of it as a bug, since the vector ABI
> specification is still being worked out and isn't stable and currently used
> with vector arguments will throw a warning about unstable.

Yes but other targets had bugs in argument passing and now throw a warning
about the change ... Plus there is no current -Wpsabi warning in previous
versions of GCC ....

[Bug target/113240] Use wrong rule to pass fixed-length(size<=2*XLEN) vector argument

[lehua.ding at rivai dot ai]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113240

--- Comment #4 from Lehua Ding <lehua.ding at rivai dot ai> ---
(In reply to Andrew Pinski from comment #3)
> (In reply to Lehua Ding from comment #2)
> > (In reply to Andrew Pinski from comment #1)
> > > There needs to be a -Wabi warning for this too for the change between
> > > versions.
> > 
> > I'm more inclined to think of it as a bug, since the vector ABI
> > specification is still being worked out and isn't stable and currently used
> > with vector arguments will throw a warning about unstable.
> 
> Yes but other targets had bugs in argument passing and now throw a warning
> about the change ... Plus there is no current -Wpsabi warning in previous
> versions of GCC ....

OK, makes sense.

[Bug target/113240] Use wrong rule to pass fixed-length(size<=2*XLEN) vector argument

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113240

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2024-01-05
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
.

[Bug target/113240] Use wrong rule to pass fixed-length(size<=2*XLEN) vector argument

[kito at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113240

--- Comment #6 from Kito Cheng <kito at gcc dot gnu.org> ---
> There needs to be a -Wabi warning for this too for the change between versions.

This bug only happened on trunk, and GCC 13 is OK, so I think it's not the
case?