[InstCombine] (m+m)/(m) is not optimized when m=a+a+a, but it is for m=a+a

[ZY546]

https://godbolt.org/z/Y84oh497E

int m, n;
void func(int a){

    m=a+a+a;
    n=(m+m)/(m);
}

We note that the expression (m+m)/m is optimized to 2 if the number of a in the expression assigned to m is 2ⁿ, otherwise it is not optimized.

proof:
https://alive2.llvm.org/ce/z/y9amEc