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From: "ndesaulniers at google dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/110728] should __attribute__((cleanup())) callback
 get invoked for indirect edges of asm goto
Date: Thu, 03 Aug 2023 16:00:44 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110728

--- Comment #10 from Nick Desaulniers <ndesaulniers at google dot com> ---
(In reply to Michael Matz from comment #9)
> That has to do with how we need to (possibly)
> split
> critical edges, which changes label identity, which in turn might actually
> be the thing that's required by the asmgoto.

(Addressing just this point for now.)

I don't think that's a problem for users of asm goto; GCC (and Clang) will
already split critical edges when using asm goto with outputs (thus creating
the case you describe where the label that the asm will jump to has been
synthesized and may differ from the final actual destination).

For example:

```c
void bar (void);

int foo (int y) {
    int x;

    if (y)
        goto end;

    asm goto ("# %1 %2":"=3Dr"(x):"i"(&&end)::end);
    bar();
    return 0;
end:
    return x;
}
```

in the above, %1 may not equal %2.

I documented this behavior in clang
https://github.com/llvm/llvm-project/commit/329ef60f3e21fd6845e8e8b0da405ca=
e7eb27267#diff-ec770381d76c859f5f572db789175fe44410a72608f58ad5dbb14335ba56=
eb97
which will be in the clang-17 release notes once clang-17 ships (currently =
in
-rc).

I also don't see that being a problem for the Linux kernel at the moment,
though they may need to consider that behavior.=