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From: "david.spickett at linaro dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/108691] [13 Regression] ICE with function ptr
 and setjmp/returns twice at -O1
Date: Mon, 13 Feb 2023 09:51:54 +0000
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X-Bugzilla-Keywords: ice-on-valid-code, needs-bisection
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108691

--- Comment #7 from David Spickett <david.spickett at linaro dot org> ---
> That still leaves us with missing abnormal edges - David, was this reduce=
d from an actual program?

No, it's a simplified version of the C used to generate an LLVM IR test cas=
e:
extern int setjmp(ptr);
extern void notsetjmp(void);

void bbb(void) {
  setjmp(0);
  int (*fnptr)(ptr) =3D setjmp;
  fnptr(0);
  notsetjmp();
}

The test is checking that llvm follows each call to a returns twice function
with a branch target identifier instruction. In case the function returns u=
sing
a jump instead of the normal ret. That's probably beside the point for this=
 bug
though.

The "real code" that motivated the feature was not doing indirect calls. I =
just
tested that because there's no reason it shouldn't also work.

I don't know of a use case for code like this. Like you said, if the compil=
er
doesn't know what the indirect call target is, it won't know it's return tw=
ice.
If it does know what you're calling, you could probably just call it direct=
ly.

So I was just shuffling statements around to test clang and compare against=
 gcc
and found the ICE that way.=