https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106864
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Take:
void bad() {
constexpr int x = 123;
auto Outer = [&] [[gnu::noipa]] () {
auto L = [=] [[gnu::noipa]] () {
const int *x1 = &x;
for (int i = 0; i < *x1; ++i) { asm("":::"memory"); }
};
asm("":::"memory");
L();
};
Outer();
}
void good() {
constexpr int x = 123;
auto L = [=] [[gnu::noipa]]() {
const int *x1 = &x;
for (int i = 0; i < *x1; ++i) {asm("":::"memory"); }
};
L();
}
In the bad case, L is sizeof int and Outer is still 1. In good, it is sizeof
int.
This is for GCC and clang.
So I think GCC is just capturing and not removing constexpr after doing the
prop for constexpr. Which I think is just a missed optimization.
