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From: "rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/108357] [13 Regression] Dead Code Elimination
 Regression at -O2 since r13-4607-g2dc5d6b1e7ec88
Date: Thu, 13 Apr 2023 13:05:07 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108357

--- Comment #13 from rguenther at suse dot de <rguenther at suse dot de> ---
On Thu, 13 Apr 2023, chenglulu at loongson dot cn wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108357
>=20
> --- Comment #10 from chenglulu <chenglulu at loongson dot cn> ---
> (In reply to Xi Ruoyao from comment #5)
> > The test fails on loongarch64-linux-gnu.  foo is kept in 114t.threadful=
l1,
> > but removed in 135t.forwprop3.
> >=20
> > Does this mean something is wrong for LoongArch, or we should simply ch=
eck
> > the tree dump in a later pass (for e.g. 254t.optimized)?
>=20
> If the definition of the macro DEFAULT_SIGNED_CHAR is changed to 0, the t=
est
> case can pass the test. I guess it is because the definition of
> DEFAULT_SIGNED_CHAR affects the optimization of the ccp pass, resulting i=
n some
> blocks that cannot be removed, resulting in the failure of this test case.

Can you check if making b unsigned fixes the test for you?  If so
that's what we should do.=