[Bug target/79754] ICE in type_natural_mode with vector for DFP type

["zsojka at seznam dot cz" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79754

--- Comment #3 from Zdenek Sojka <zsojka at seznam dot cz> ---
This still ICEs on r12-7199:
$ x86_64-pc-linux-gnu-gcc testcase.c 
testcase.c: In function 'foo':
testcase.c:2:1: internal compiler error: in type_natural_mode, at
config/i386/i386.cc:1978
    2 | V foo (V a) { return a * a; }
      | ^
0x81e1e7 type_natural_mode
        /repo/gcc-trunk/gcc/config/i386/i386.cc:1978
0x172382a ix86_return_in_memory
        /repo/gcc-trunk/gcc/config/i386/i386.cc:4230
0x101084d aggregate_value_p(tree_node const*, tree_node const*)
        /repo/gcc-trunk/gcc/function.cc:2119
0x10154ac allocate_struct_function(tree_node*, bool)
        /repo/gcc-trunk/gcc/function.cc:4845
0xd26104 store_parm_decls()
        /repo/gcc-trunk/gcc/c/c-decl.cc:10160
0xd855c7 c_parser_declaration_or_fndef
        /repo/gcc-trunk/gcc/c/c-parser.cc:2505
0xd8d8a3 c_parser_external_declaration
        /repo/gcc-trunk/gcc/c/c-parser.cc:1779
0xd8e2eb c_parser_translation_unit
        /repo/gcc-trunk/gcc/c/c-parser.cc:1652
0xd8e2eb c_parse_file()
        /repo/gcc-trunk/gcc/c/c-parser.cc:23348
0xdef9fd c_common_parse_file()
        /repo/gcc-trunk/gcc/c-family/c-opts.cc:1238
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but works on powerpc64le (at least, doesn't ICE; I didn't check if the code is
correct):
$ powerpc64le-unknown-linux-gnu-gcc testcase.c -c
(no output)