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From: "segher at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/112758] [13/14 Regression] Inconsistent Bitwise AND Operation Result between int and long long int
Date: Sun, 10 Dec 2023 12:16:12 +0000 [thread overview]
Message-ID: <bug-112758-4-RLkaFXCtAE@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-112758-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112758
--- Comment #12 from Segher Boessenkool <segher at gcc dot gnu.org> ---
(In reply to Eric Botcazou from comment #11)
> > It says those upper bits are well-defined, i.e. whatever MD pattern is used
> > for it eventually will emit machine code that has the exact same result for
> > those upper bits.
>
> No, that's not true, the set of "register operations" is restricted.
Who what where? That is not how it is documented. There is
word_register_operation_p as a bandaid to make it *somewhat* work, added
decades
later, but it still won't fly :-(
Different parts of the compiler think it has much more stringent semantics btw.
next prev parent reply other threads:[~2023-12-10 12:16 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-29 6:05 [Bug c/112758] New: Inconsistent Bitwise AND Operation Result between int and long long int on Different Optimization Levels in GCC Trunk guminb at ajou dot ac.kr
2023-11-29 18:18 ` [Bug rtl-optimization/112758] [13/14 Regression] Inconsistent Bitwise AND Operation Result between int and long long int pinskia at gcc dot gnu.org
2023-12-08 2:57 ` guminb at ajou dot ac.kr
2023-12-08 17:01 ` jakub at gcc dot gnu.org
2023-12-08 17:37 ` segher at gcc dot gnu.org
2023-12-08 19:33 ` jakub at gcc dot gnu.org
2023-12-08 19:36 ` jakub at gcc dot gnu.org
2023-12-09 8:51 ` ebotcazou at gcc dot gnu.org
2023-12-09 9:11 ` jakub at gcc dot gnu.org
2023-12-09 11:00 ` ebotcazou at gcc dot gnu.org
2023-12-09 19:25 ` segher at gcc dot gnu.org
2023-12-09 22:06 ` ebotcazou at gcc dot gnu.org
2023-12-10 12:16 ` segher at gcc dot gnu.org [this message]
2023-12-13 22:06 ` pinskia at gcc dot gnu.org
2023-12-16 18:43 ` gkm at rivosinc dot com
2023-12-21 20:04 ` gkm at rivosinc dot com
2023-12-21 20:06 ` jakub at gcc dot gnu.org
2023-12-22 11:30 ` cvs-commit at gcc dot gnu.org
2024-03-02 0:37 ` cvs-commit at gcc dot gnu.org
2024-03-04 1:09 ` law at gcc dot gnu.org
2024-03-04 12:07 ` [Bug rtl-optimization/112758] [13 " jakub at gcc dot gnu.org
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