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From: "ubizjak at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/102143] ABI incompatibility with clang when passing
 32bit vectors on 32bit i686
Date: Wed, 01 Sep 2021 07:33:46 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102143

--- Comment #5 from Uro=C5=A1 Bizjak <ubizjak at gmail dot com> ---
(In reply to Uro=C5=A1 Bizjak from comment #3)
> gcc has also some problems in this area. With -mregparm=3D3, one would ex=
pect
> arguments obeying integer ABI to be passed in registers, but regparm flag
> has no effect and the same code is produced:
>=20
> foo:
>         movd    4(%esp), %xmm0
>         movd    8(%esp), %xmm1
>         paddw   %xmm1, %xmm0
>         movd    %xmm0, %eax
>         ret

(sorry, sent the message too fast)

However, with -mno-sse -mregparm=3D3, regparm does have effect and produces:

foo:
        leal    (%eax,%edx), %ecx
        sarl    $16, %eax
        sarl    $16, %edx
        addl    %eax, %edx
        movzwl  %cx, %eax
        sall    $16, %edx
        orl     %edx, %eax
        ret

vs -mno-sse -mregparm=3D0:

foo:
        movl    4(%esp), %edx
        movl    8(%esp), %ecx
        leal    (%edx,%ecx), %eax
        sarl    $16, %edx
        sarl    $16, %ecx
        addl    %ecx, %edx
        movzwl  %ax, %eax
        sall    $16, %edx
        orl     %edx, %eax
        ret=