[Bug tree-optimization/81248] No ipa-sra optimization for small struct / class

[wilhelm.me...@hs-kl.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81248

--- Comment #4 from wilhelm.me...@hs-kl.de ---
Here a more stripped down example (without the volatile part):

#include <cstdint>
#include <type_traits>

struct A {
    uint8_t m1{0};
};

volatile uint8_t v;

template<typename T>
void f(const T& x) __attribute__((noinline));
template<typename T>
void f(const T& x) {
    if constexpr(std::is_same<T, A>::value) {
        v = x.m1;
    }
    else {
        v = x;
    }
}

uint8_t n1;
A n2;

int main() {
    f(n1);
    f(n2);
}