From: Jisheng Zhang Date: Tue, 21 Nov 2023 14:43:40 +0000 (+0800) Subject: riscv: select ARCH_HAS_FAST_MULTIPLIER X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=f617cf019d9afd555904624b248de80a5cd0b8cc;p=platform%2Fkernel%2Flinux-thead.git riscv: select ARCH_HAS_FAST_MULTIPLIER Currently, riscv linux requires at least IMA, so all platforms have a multiplier. And I assume the 'mul' efficiency is comparable or better than a sequence of five or so register-dependent arithmetic instructions. Select ARCH_HAS_FAST_MULTIPLIER to get slightly nicer codegen. Refer to commit f9b4192923fa ("[PATCH] bitops: hweight() speedup") for more details. In a simple benchmark test calling hweight64() in a loop, it got: about 14% preformance improvement on JH7110, tested on Milkv Mars. about 23% performance improvement on TH1520 and SG2042, tested on Sipeed LPI4A and SG2042 platform. a slight performance drop on CV1800B, tested on milkv duo. Among all riscv platforms in my hands, this is the only one which sees a slight performance drop. It means the 'mul' isn't quick enough. However, the situation exists on x86 too, for example, P4 doesn't have fast integer multiplies as said in the above commit, x86 also selects ARCH_HAS_FAST_MULTIPLIER. So let's select ARCH_HAS_FAST_MULTIPLIER which can benefit almost riscv platforms. Signed-off-by: Jisheng Zhang Reviewed-by: Samuel Holland Tested-by: Samuel Holland (cherry picked from commit b25b9b6b16dda999311ae1d785321c2f5c0d0a63) Signed-off-by: Jaehoon Chung --- diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 8eb0a52d3ddf..720f7a351e43 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -18,6 +18,7 @@ config RISCV select ARCH_HAS_DEBUG_VM_PGTABLE select ARCH_HAS_DEBUG_VIRTUAL if MMU select ARCH_HAS_DEBUG_WX + select ARCH_HAS_FAST_MULTIPLIER select ARCH_HAS_GCOV_PROFILE_ALL select ARCH_HAS_GIGANTIC_PAGE select ARCH_HAS_KCOV