[Bug target/102105] x86_64: ABI break with vector in union and -mno-mmx -mavx

[hjl.tools at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102105

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Version|unknown                     |9.4.1
            Summary|[10/11/12 Regression]       |x86_64: ABI break with
                   |x86_64: ABI break with      |vector in union and
                   |vector in union and         |-mno-mmx -mavx
                   |-mno-mmx -mavx              |

--- Comment #2 from H.J. Lu <hjl.tools at gmail dot com> ---
I consider this is a GCC 9 bug:

[hjl@gnu-cfl-2 pr102105]$ cat foo.c
extern __attribute__((__vector_size__(8))) long long g_v1di;
void pass_v1di( __attribute__((__vector_size__(8))) long long);
void test_v1di() { pass_v1di(g_v1di); }
[hjl@gnu-cfl-2 pr102105]$ /usr/gcc-9.3.1-x32/bin/gcc -S -O2 foo.c
[hjl@gnu-cfl-2 pr102105]$ cat foo.s
        .file   "foo.c"
        .text
        .p2align 4
        .globl  test_v1di
        .type   test_v1di, @function
test_v1di:
.LFB0:
        .cfi_startproc
        movq    g_v1di(%rip), %xmm0
        jmp     pass_v1di
        .cfi_endproc
.LFE0:
        .size   test_v1di, .-test_v1di
        .ident  "GCC: (GNU) 9.3.1 20200312"
        .section        .note.GNU-stack,"",@progbits
[hjl@gnu-cfl-2 pr102105]$ /usr/gcc-9.3.1-x32/bin/gcc -S -O2 foo.c -mno-mmx
[hjl@gnu-cfl-2 pr102105]$ cat foo.s
        .file   "foo.c"
        .text
        .p2align 4
        .globl  test_v1di
        .type   test_v1di, @function
test_v1di:
.LFB0:
        .cfi_startproc
        movq    g_v1di(%rip), %rdi
        jmp     pass_v1di
        .cfi_endproc
.LFE0:
        .size   test_v1di, .-test_v1di
        .ident  "GCC: (GNU) 9.3.1 20200312"
        .section        .note.GNU-stack,"",@progbits
[hjl@gnu-cfl-2 pr102105]$ 

Since MMX register isn't used, -mno-mmx shouldn't change ABI.