target/riscv: warning on current master: writing 8 bytes into a region of size 4

["Richard W.M. Jones" <rjones@redhat.com>]

When compiling the latest master branch, CONFIG_ATOMIC64 is defined,
and I get this warning:

----
In function ‘stq_he_p’,
    inlined from ‘translator_ld’ at ../accel/tcg/translator.c:359:13,
    inlined from ‘translator_ldl_end’ at ../accel/tcg/translator.c:491:10,
    inlined from ‘translator_ldl’ at /home/rjones/d/qemu/include/exec/translator.h:201:12,
    inlined from ‘decode_opc’ at ../target/riscv/translate.c:1236:18,
    inlined from ‘riscv_tr_translate_insn’ at ../target/riscv/translate.c:1348:5:
/home/rjones/d/qemu/include/qemu/bswap.h:295:5: warning: writing 8 bytes into a region of size 4 [-Wstringop-overflow=]
  295 |     __builtin_memcpy(ptr, &v, sizeof(v));
      |     ^
../accel/tcg/translator.c: In function ‘riscv_tr_translate_insn’:
../accel/tcg/translator.c:489:14: note: destination object ‘val’ of size 4
  489 |     uint32_t val;
      |              ^
../accel/tcg/translator.c:489:14: note: at offset [1, 4] into destination object ‘val’ of size 4
----

Looking at the code I can see why it's happening.  However I don't see
a simple fix.

The function 'translator_ldl_end' really wants a 32 bit result, and it
seems like the 64 bit case would never be called, although I'm not
sure ...

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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