c++ - Impossible Register Constraint in asm

Question

I am trying to use this code for multiplication in a C++ file.

LL mul(LL a, LL b, LL m)
{
   LL q;
   LL r;
   asm( "mulq %3;"
   "divq %4;"
   : "=a"(q), "=d"(r)
   : "a"(a), "rm"(b), "rm"(m));
   return r;
}

But this is showing impossible register constraint in asm error.

Answer 1

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