[llvm-bugs] [Bug 27081] New: invalid instruction generated for atomic store of __int128 on aarch64

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=27081

            Bug ID: 27081
           Summary: invalid instruction generated for atomic store of
                    __int128 on aarch64
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: AArch64
          Assignee: unassignedbugs at nondot.org
          Reporter: yyc1992 at gmail.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

The following program generates an invalid instruction on llvm trunk.

```
#include <atomic>
#include <stdint.h>

std::atomic<__int128> a;

__attribute__((noinline)) void f(int64_t v)
{
    a.store(v);
}

int main()
{
    f(1);
    return 0;
}
```

The assembly is

```
0000000000400610 <_Z1fl>:
  400610:       90000089        adrp    x9, 410000 <__FRAME_END__+0xf8a0>
  400614:       937ffc08        asr     x8, x0, #63
  400618:       91278129        add     x9, x9, #0x9e0
  40061c:       c87ffd3f        ldaxp   xzr, xzr, [x9]
  400620:       c82aa120        stlxp   w10, x0, x8, [x9]
  400624:       35ffffca        cbnz    w10, 40061c <_Z1fl+0xc>
  400628:       d65f03c0        ret
```

And the `ldaxp` instruction raise a SIGILL.

(GCC raises a linker error in this case...)

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