[Bug target/114416] calling convention incompatibility with vendor compiler for V9

["jakub.kulik at oracle dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114416

Jakub Kulik <jakub.kulik at oracle dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |jakub.kulik at oracle dot com

--- Comment #6 from Jakub Kulik <jakub.kulik at oracle dot com> ---
Thank you for the proposed fix! I tested it with several programs that I used
to find/reproduce the issue and it seems to work now (I talked about this with
Rainer initially).

As for the ABI being potentially unclear, I am in no way a SPARCv9 ABI expert,
so I asked internally, and was told that the ABI should be clear about this
case:

"""
See page 3P-10 (PDF page 46) where it says this:

%f0,%f1,%f2,%f3
(%d0, %d2)
(%q0)
Floating-point return values appear in the floating-point registers.
Single-precision values occupy %f0; double-precision values occupy %d0;
quad-precision values occupy %q0. (Refer to the SPARCTM Architecture Manual,
Version 9 for details on the register numbering scheme). Otherwise, these are
scratch registers.

and

%f0 through %f7
(%d0 through %d6)
(%q0 and %q4)
Floating-point fields from structure return values with a total size of 32
bytes or less appear in the floating-point registers.

Then on page 3P-13 (PDF page 49) it says this:
Structure or Union return values
Structure and union return types up to thirty-two bytes in size are returned in
registers. The registers are assigned as if the value was being passed as the
first argument to a function with a known prototype.

So we have to refer back to "Structure and Union arguments" on page 3P-12 (PDF
page 48) where it says:

"Structure or union types are always left-justified, whether stored in
registers or memory. *The individual fields of a structure (or containing
storage unit in the case of bit fields) are subject to promotion into registers
based on their type using the same rules as apply to scalar values* (with the
addition that a single-precision floating-point number assigned to the left
half of an argument slot will be promoted into the corresponding even-numbered
float register.)." [sic; emphasis added.] 
"""