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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Thu, Aug 21, 2025 at 05:16:34PM +0800, Vivian Wang wrote: > Use __riscv_has_extension_likely() to check for RISCV_ISA_EXT_ZBB, > replacing the use of asm goto with ALTERNATIVE. > > The "likely" variant is used to match the behavior of the original > implementation using ALTERNATIVE("j %l[legacy]", "nop", ...). > > Signed-off-by: Vivian Wang > --- > arch/riscv/include/asm/bitops.h | 32 ++++++++------------------------ > 1 file changed, 8 insertions(+), 24 deletions(-) > > diff --git a/arch/riscv/include/asm/bitops.h b/arch/riscv/include/asm/bitops.h > index d59310f74c2ba70caeb7b9b0e9221882117583f5..f70ccc0c2ffb86a6fda3bc373504143d0c6a1093 100644 > --- a/arch/riscv/include/asm/bitops.h > +++ b/arch/riscv/include/asm/bitops.h > @@ -47,9 +47,8 @@ > > static __always_inline unsigned long variable__ffs(unsigned long word) > { > - asm goto(ALTERNATIVE("j %l[legacy]", "nop", 0, > - RISCV_ISA_EXT_ZBB, 1) > - : : : : legacy); > + if (!__riscv_has_extension_likely(0, RISCV_ISA_EXT_ZBB)) > + return generic___ffs(word); So, on the previous round you spent quite a lot of time explaining how 'unlikely()' version is handy over '!likely()', and now use just the latter. I feel really lost about how the code generation should look. Can you please share bloat-o-meter report against this patch? Can you also show an example of code generation before and after? Have you tried the 'unlikely()` one? How the output looks? > asm volatile (".option push\n" > ".option arch,+zbb\n" Yeah, now the diff is much cleaner. 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Thu, 21 Aug 2025 07:44:07 -0700 (PDT) Date: Thu, 21 Aug 2025 10:44:05 -0400 From: Yury Norov To: Vivian Wang Cc: Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Rasmus Villemoes , Charlie Jenkins , Xiao Wang , Christoph =?iso-8859-1?Q?M=FCllner?= , Vivian Wang , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 4/5] riscv: bitops: Use __riscv_has_extension_likely Message-ID: References: <20250821-riscv-altn-helper-wip-v2-0-9586fa702f78@iscas.ac.cn> <20250821-riscv-altn-helper-wip-v2-4-9586fa702f78@iscas.ac.cn> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250821-riscv-altn-helper-wip-v2-4-9586fa702f78@iscas.ac.cn> On Thu, Aug 21, 2025 at 05:16:34PM +0800, Vivian Wang wrote: > Use __riscv_has_extension_likely() to check for RISCV_ISA_EXT_ZBB, > replacing the use of asm goto with ALTERNATIVE. > > The "likely" variant is used to match the behavior of the original > implementation using ALTERNATIVE("j %l[legacy]", "nop", ...). > > Signed-off-by: Vivian Wang > --- > arch/riscv/include/asm/bitops.h | 32 ++++++++------------------------ > 1 file changed, 8 insertions(+), 24 deletions(-) > > diff --git a/arch/riscv/include/asm/bitops.h b/arch/riscv/include/asm/bitops.h > index d59310f74c2ba70caeb7b9b0e9221882117583f5..f70ccc0c2ffb86a6fda3bc373504143d0c6a1093 100644 > --- a/arch/riscv/include/asm/bitops.h > +++ b/arch/riscv/include/asm/bitops.h > @@ -47,9 +47,8 @@ > > static __always_inline unsigned long variable__ffs(unsigned long word) > { > - asm goto(ALTERNATIVE("j %l[legacy]", "nop", 0, > - RISCV_ISA_EXT_ZBB, 1) > - : : : : legacy); > + if (!__riscv_has_extension_likely(0, RISCV_ISA_EXT_ZBB)) > + return generic___ffs(word); So, on the previous round you spent quite a lot of time explaining how 'unlikely()' version is handy over '!likely()', and now use just the latter. I feel really lost about how the code generation should look. Can you please share bloat-o-meter report against this patch? Can you also show an example of code generation before and after? Have you tried the 'unlikely()` one? How the output looks? > asm volatile (".option push\n" > ".option arch,+zbb\n" Yeah, now the diff is much cleaner. Thanks.