Bug#943396: FTBFS on armhf: testsuite segfault

[Bernhard Übelacker]

Dear Maintainer,
I tried to reproduce and collect some more details.
Following was done on a Lineageos kernel inside a
armhf testing chroot.

Building with CC=gcc-8 is finishing ok.
The segfault just appears with CC=gcc-9.
And a build with CC=gcc-10 ends with a compiler bug interestingly
also in common/n1fv_9.c.

I think the issue with gcc-9 points to the instruction below.
There the vst1.32 stores into $r3 the sum of $r3 and $r3,
basically doubling the address of a pointer.
The segfault happens apparently when this pointer is dereferenced later.
This original pointer in $r3 is based on the value in "ro" variable.

Kind regards,
Bernhard


    (gdb) 
    0xb6f137c4 in vst1_f32 (__b=..., __a=0x7f5cfbb0) at /usr/lib/gcc/arm-linux-gnueabihf/9/include/arm_neon.h:10876
    10876     __builtin_neon_vst1v2sf ((__builtin_neon_sf *) __a, __b);
    1: x/i $pc
    => 0xb6f137c4 <n1fv_9+740>:     vst1.32 {d12}, [r3], r3
    4: /x $r3 = 0x7f5cfbb0
    8: /x $d12 = {u8 = {0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0}, u16 = {0x0, 0x0, 0x0, 0x0}, u32 = {0x0, 0x0}, u64 = 0x0, f32 = {0x0, 0x0}, f64 = 0x0}
    (gdb) 
    n1fv_9 (ri=<optimized out>, ii=<optimized out>, ro=<optimized out>, io=<optimized out>, is=<optimized out>, os=2, v=2, ivs=2, ovs=18) at /usr/lib/gcc/arm-linux-gnueabihf/9/include/arm_neon.h:16772
    16772     return (uint32x4_t)__a;
    1: x/i $pc
    => 0xb6f137c8 <n1fv_9+744>:     mla     lr, lr, r4, r3
    4: /x $r3 = 0xfeb9f760
    (gdb) 
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