[Bug tree-optimization/89478] missed optimization for lambda expression when variable is uninitialized when declared

[SztfG at yandex dot ru]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89478

--- Comment #3 from SztfG at yandex dot ru ---
Another testcase:
int test4 = []() constexpr {int a = a; a = 5; return a;}();

GCC is able compile this, so it "think" this is valid constexpr lambda, but
anyway doing this:

_GLOBAL__sub_I_test4:
movl$5, test4(%rip)
ret
test4:
.zero   4

[Bug tree-optimization/89478] missed optimization for lambda expression when variable is uninitialized when declared

[SztfG at yandex dot ru]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89478

--- Comment #2 from SztfG at yandex dot ru ---
(In reply to Marc Glisse from comment #1)
> I think the uninitialized variable makes the initialization not constexpr
> (and indeed gcc/clang complain if you try to declare test constexpr). Then
> we hit the well-known missed optimization that gcc is unable to convert a
> dynamic initialization into a static initialization even in the most trivial
> constant cases.

Then need to mark this bug as duplicate, but where that bug in GCC bugzilla,
which about that well-known missed optimization?

[Bug tree-optimization/89478] missed optimization for lambda expression when variable is uninitialized when declared

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89478

--- Comment #1 from Marc Glisse  ---
I think the uninitialized variable makes the initialization not constexpr (and
indeed gcc/clang complain if you try to declare test constexpr). Then we hit
the well-known missed optimization that gcc is unable to convert a dynamic
initialization into a static initialization even in the most trivial constant
cases.