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From: "vineetg at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/110748] RISC-V: optimize store of DF 0.0
Date: Thu, 20 Jul 2023 17:38:10 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110748

--- Comment #9 from Vineet Gupta <vineetg at gcc dot gnu.org> ---
(In reply to Vineet Gupta from comment #8)
> (In reply to Jeffrey A. Law from comment #5)
> > I'd bet it's const_0_operand not allowing CONST_DOUBLE.
>=20
> Correct.
>=20
> > The question is what unintended side effects we'd have if we allowed
> > CONST_DOUBLE 0.0 in const_0_operand.
>=20
> Exactly. I had the same concern.=20

[...]

> However to Kito's point, this indeed works in gcc 12 so I first need to
> bisect what regressed it in 13.

The mystery is solved. Guess what it was my change ef85d150b5963 ("RISC-V:
Enable TARGET_SUPPORTS_WIDE_INT") in gcc-13 cycle which made the booboo.

+            * config/riscv/predicates.md (const_0_operand): Remove
+            const_double.

And I don't recall why I did that part. But I guess reinstating it back won=
't
be that radical, since it wa sin tree for a while. I'll throw it at full
testsuite to see if there are any fallouts.=