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d="asc'?scan'208";a="20728192" X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN Received: from unknown (HELO email.microchip.com) ([170.129.1.10]) by esa3.microchip.iphmx.com with ESMTP/TLS/ECDHE-RSA-AES128-GCM-SHA256; 12 Apr 2024 03:42:02 -0700 Received: from chn-vm-ex01.mchp-main.com (10.10.85.143) by chn-vm-ex02.mchp-main.com (10.10.85.144) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.35; Fri, 12 Apr 2024 03:41:33 -0700 Received: from wendy (10.10.85.11) by chn-vm-ex01.mchp-main.com (10.10.85.143) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.35 via Frontend Transport; Fri, 12 Apr 2024 03:41:29 -0700 Date: Fri, 12 Apr 2024 11:40:38 +0100 From: Conor Dooley To: Charlie Jenkins CC: Conor Dooley , Rob Herring , Krzysztof Kozlowski , Paul Walmsley , Palmer Dabbelt , Albert Ou , Guo Ren , Conor Dooley , Chen-Yu Tsai , Jernej Skrabec , Samuel Holland , Evan Green , =?iso-8859-1?Q?Cl=E9ment_L=E9ger?= , Jonathan Corbet , Shuah Khan , , , , Palmer Dabbelt , , , , Subject: Re: [PATCH 07/19] riscv: Optimize riscv_cpu_isa_extension_(un)likely() Message-ID: <20240412-aerosol-heritage-cec1eca172fb@wendy> References: <20240411-dev-charlie-support_thead_vector_6_9-v1-0-4af9815ec746@rivosinc.com> <20240411-dev-charlie-support_thead_vector_6_9-v1-7-4af9815ec746@rivosinc.com> MIME-Version: 1.0 In-Reply-To: <20240411-dev-charlie-support_thead_vector_6_9-v1-7-4af9815ec746@rivosinc.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240412_034204_073770_7ECA8B9D X-CRM114-Status: GOOD ( 17.25 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: multipart/mixed; boundary="===============0905638962839443296==" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org --===============0905638962839443296== Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="YUt35LWoARaS+0kq" Content-Disposition: inline --YUt35LWoARaS+0kq Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Apr 11, 2024 at 09:11:13PM -0700, Charlie Jenkins wrote: > When alternatives are disabled, riscv_cpu_isa_extension_(un)likely() > checks if the current cpu supports the selected extension if not all > cpus support the extension. It is sufficient to only check if the > current cpu supports the extension. >=20 > The alternatives code to handle if all cpus support an extension is > factored out into a new function to support this. >=20 > Signed-off-by: Charlie Jenkins > --- > static __always_inline bool riscv_cpu_has_extension_unlikely(int cpu, co= nst unsigned long ext) > { > - if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE) && riscv_has_extension_unlikel= y(ext)) > - return true; > + compiletime_assert(ext < RISCV_ISA_EXT_MAX, > + "ext must be < RISCV_ISA_EXT_MAX"); > =20 > - return __riscv_isa_extension_available(hart_isa[cpu].isa, ext); > + if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE) && __riscv_has_extension_unlik= ely_alternatives(ext)) > + return true; > + else > + return __riscv_isa_extension_available(hart_isa[cpu].isa, ext); > } static __always_inline bool riscv_cpu_has_extension_likely(int cpu, const u= nsigned long ext) { if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE) && riscv_has_extension_likely(ext= )) return true; return __riscv_isa_extension_available(hart_isa[cpu].isa, ext); } This is the code as things stand. If alternatives are disabled, the if statement becomes if (0 && foo) which will lead to the function call getting constant folded away and all you end up with is the call to __riscv_isa_extension_available(). Unless I am missing something, I don't think this patch has any affect? Thanks, Conor. --YUt35LWoARaS+0kq Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQRh246EGq/8RLhDjO14tDGHoIJi0gUCZhkPpgAKCRB4tDGHoIJi 0gSNAQC+oMqT7zoEL9RxUhkl7uImpatcHajgjd6QJ8PnV2xTcgD/YMRe1XytJnd7 9pJBNiy2EcDN51fcQvf7s4vI9GM9Awc= =Tq3D -----END PGP SIGNATURE----- --YUt35LWoARaS+0kq-- --===============0905638962839443296== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel --===============0905638962839443296==--