[Bug c/126552] const-qualified local register variable used as an asm operand is silently discarded

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D126552

--- Comment #9 from Bernie Innocenti <bernie at codewiz dot org> ---
I tried dropping the const qualifier with __typeof_unqual__(),
but it's unavailable on GCC 13, so instead I'm using this:

  #define DROP_CONST(t) __typeof__((t)0)

Then, this produces the expected code with all three compiler versions:

#define LP7NR(offs, name, t1, v1, r1, t2, v2, r2, t3, v3, r3, t4, v4, r4, t=
5,
v5, r5, t6, v6, r6, t7, v7, r7, bt, bn) \
({                                      \
   t1 _##name##_v1 =3D (v1);              \
   t2 _##name##_v2 =3D (v2);              \
   t3 _##name##_v3 =3D (v3);              \
   t4 _##name##_v4 =3D (v4);              \
   t5 _##name##_v5 =3D (v5);              \
   t6 _##name##_v6 =3D (v6);              \
   t7 _##name##_v7 =3D (v7);              \
   {                                    \
      register int _d0 __asm("d0");     \
      register int _d1 __asm("d1");     \
      register int _a0 __asm("a0");     \
      register int _a1 __asm("a1");     \
      register DROP_CONST(t3) _n3 __asm(#r3) =3D _##name##_v3; \
      register DROP_CONST(t4) _n4 __asm(#r4) =3D _##name##_v4; \
      register DROP_CONST(t5) _n5 __asm(#r5) =3D _##name##_v5; \
      register DROP_CONST(t6) _n6 __asm(#r6) =3D _##name##_v6; \
      register DROP_CONST(t7) _n7 __asm(#r7) =3D _##name##_v7; \
      register DROP_CONST(t1) _n1 __asm(#r1) =3D _##name##_v1; \
      register DROP_CONST(t2) _n2 __asm(#r2) =3D _##name##_v2; \
      register void *const _##name##_bn __asm("a6") =3D (bn); \
      __asm volatile ("jsr a6@(-"#offs":W)" \
      : "=3Dr" (_d0), "=3Dr" (_d1), "=3Dr" (_a0), "=3Dr" (_a1) \
      : "r" (_##name##_bn), "rf"(_n1), "rf"(_n2), "rf"(_n3), "rf"(_n4),
"rf"(_n5), "rf"(_n6), "rf"(_n7) \
      : "fp0", "fp1", "cc", "memory"); \
   } \
})=