https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103830
--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
To clarify myself - the testcase is invoking UB, 'volatile' doesn't make a
difference here. That we get the DSE as a second-order effect is unfortunate
at most, in other places we try to preserve volatile qualified accesses. But I
do not think it's worth to pessimize -Og for that. If you declare
MyClass::call() noinline you get the same behavior with all optimization
levels:
struct MyClass;
struct ptr {
MyClass* get() { return t; } /* line 21 */
MyClass* t;
};
struct MyClass { void __attribute__((noinline)) call(); };
void MyClass::call() {
*(volatile char*)(nullptr) = 1; /* line 26 */
}
static void intermediate(ptr p) {
p.get()->call(); /* line 29 */
}
int main() {
intermediate(ptr{new MyClass});
}
so iff then we need to argue about the modref/ipa-pure-const behavior, not
about DCE of calls at -Og.
