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From: "rsandifo at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/109661] [13/14 Regression] ICE in
 aarch64_function_arg_alignment when building erlang
Date: Fri, 28 Apr 2023 08:56:46 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109661

--- Comment #4 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.or=
g> ---
Yeah, I'd come up with essentially the same fix locally.  Was just trying
to see whether it is an ABI problem.  And I think it is.  For:

typedef unsigned long U __attribute__ ((aligned (16)));
typedef enum : U { V =3D 0 } W;

U
foo (int x0, int x1, int x2, int x3, int x4, int x5, int x6, int x7, U a, W=
 b)
{
  return a + b;
}

GCC aligns the b stack argument to 16 bytes:

        ldr     x1, [sp]
        ldr     x0, [sp, 16]
        add     x0, x1, x0
        ret

whereas clang doesn't:

        ldp     x8, x9, [sp]
        add     x0, x9, x8
        ret

The clang behaviour is correct, so we'll need to fix it on the GCC side.

(Neither compiler aligns for register arguments.)=