From nobody Fri Oct 31 12:48:33 2025 X-Original-To: dev-commits-src-all@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4cygl63PGkz6FmTw; Fri, 31 Oct 2025 12:48:34 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "R12" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4cygl60kJTz42XK; Fri, 31 Oct 2025 12:48:34 +0000 (UTC) (envelope-from git@FreeBSD.org) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1761914914; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=XmzAkHwc4T2xj1XpkHGQigCkl6zgLq4slYJ/bTnGX9A=; b=YKHLuCLohJnN1NWe7bAcPKLv+vnr45J/R3dmbx7+t2QNSZ3hpsAoGBVNbSfKddo4TOy7VQ KnLkSOYPInupLO4Sm3r5lEfeJ+kEB+ryzXBbJxyJBEOHq6g6wR1mqaoPxUUcoaYOZNluPT /P2myOZ2yxVT5qk1P0I4T3F34zYyeegss/RbaqiqvMvMrt++BNJ0SIImVN8dY5Q1rW/ZLy 22xmAmMwb76yqZ6MUnSrLn3OlUD1MHWvaNCmfSwafQtYQ6Miwa4DMvZvxjNX5pcnyNNR3x gwW7E3hTe1evENuWdD7DzHnBw9ZQ7AyW0ibvRIORzyYmJSiK8D8BqJ1/8nIFcw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1761914914; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=XmzAkHwc4T2xj1XpkHGQigCkl6zgLq4slYJ/bTnGX9A=; b=MQgVIcQkUwZQZeVCE3AjZ1oWSMCtZkyhHe5kvnyKvNBgmYGsz2AromENxPs4pBaZqsngSj JPFsaMdX0mj0qrxPE/sng2RaKT1wqSAIKM3eIVqGAq1n1Iv2++zUekbnQUybokj2Sz4Ux1 N8VE+WfdAQt1sJdWzTEAbuET9JMR8YuGk3RBGC5AOlPAC0uxTyKVbiQvB9cahGh1AFnGVd f4mFe0E+W7P4sERJRHP0NJkl7OoVWg9C+d0EZ1xFBccvV0EEQVlXPQPAs7M474hg7LosbD yLb2NZ+ebA9Vf42wvr0KYxOo0oy0eJrWVDDUA+ElaX5QKx18ewyQzNHjBw9i4w== ARC-Seal: i=1; s=dkim; d=freebsd.org; t=1761914914; a=rsa-sha256; cv=none; b=A2jb7GGih3HZq6B/wOXFXbwREl8MA/tVtaf7sd0PS78R/dl/iSHuL6NeOlkzyIrA+7E4QG GpxD6rn1/+eewtvfeQkc9+PUsvJ5NbpjVw4428lkLcBfzgW+a0JpCNKXzZ4WHEXpVCNSeO MY6/CKnb7GNov4Lh7G2HkLcwk+awGyf5xIvk22DVBRrVg6xZZ/oODkj71SarkWFfFX0S0d /18oHXxYRlfAOG7C76HeF27GCHvsW42GtuFDra4rzbLCR4EGIXJ/KELLrDsSL8LTVTE2py gAstaZyEDEIEb1OOQE/YeZf0wv5h3p/wnZrgzt8p3n3rqHdQEkOGmM71GcUZGg== ARC-Authentication-Results: i=1; mx1.freebsd.org; none Received: from gitrepo.freebsd.org (gitrepo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:5]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 4cygl60DKsz17p5; Fri, 31 Oct 2025 12:48:34 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from gitrepo.freebsd.org ([127.0.1.44]) by gitrepo.freebsd.org (8.18.1/8.18.1) with ESMTP id 59VCmXsE042603; Fri, 31 Oct 2025 12:48:33 GMT (envelope-from git@gitrepo.freebsd.org) Received: (from git@localhost) by gitrepo.freebsd.org (8.18.1/8.18.1/Submit) id 59VCmXvJ042600; Fri, 31 Oct 2025 12:48:33 GMT (envelope-from git) Date: Fri, 31 Oct 2025 12:48:33 GMT Message-Id: <202510311248.59VCmXvJ042600@gitrepo.freebsd.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org From: Robert Clausecker Subject: git: e09c1583eddd - main - libc: scalar strlen() in RISC-V assembly List-Id: Commit messages for all branches of the src repository List-Archive: https://lists.freebsd.org/archives/dev-commits-src-all List-Help: List-Post: List-Subscribe: List-Unsubscribe: X-BeenThere: dev-commits-src-all@freebsd.org Sender: owner-dev-commits-src-all@FreeBSD.org MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Git-Committer: fuz X-Git-Repository: src X-Git-Refname: refs/heads/main X-Git-Reftype: branch X-Git-Commit: e09c1583eddd345bdb79f3db8a91166f6f139207 Auto-Submitted: auto-generated The branch main has been updated by fuz: URL: https://cgit.FreeBSD.org/src/commit/?id=e09c1583eddd345bdb79f3db8a91166f6f139207 commit e09c1583eddd345bdb79f3db8a91166f6f139207 Author: Strahinja Stanišić AuthorDate: 2024-05-17 14:23:48 +0000 Commit: Robert Clausecker CommitDate: 2025-10-31 12:47:59 +0000 libc: scalar strlen() in RISC-V assembly Includes a scalar implementation of strlen() for the RISC-V architecture and changes to the corresponding manpage. Performance was benchamarked using before and after: https://github.com/clausecker/strperf os: FreeBSD arch: riscv │ strlen_baseline │ strlen_scalar │ │ sec/op │ sec/op vs base │ Short 541.2µ ± 17% 401.6µ ± 0% -25.78% (p=0.000 n=21+20) Mid 249.6µ ± 3% 191.9µ ± 0% -23.13% (p=0.000 n=21+20) Long 124.6µ ± 0% 110.7µ ± 0% -11.13% (p=0.000 n=21+20) geomean 256.3µ 204.3µ -20.26% │ strlen_baseline │ strlen_scalar │ │ B/s │ B/s vs base │ Short 220.3Mi ± 14% 296.8Mi ± 0% +34.74% (p=0.000 n=21+20) Mid 477.6Mi ± 3% 621.3Mi ± 0% +30.09% (p=0.000 n=21+20) Long 956.9Mi ± 0% 1076.7Mi ± 0% +12.52% (p=0.000 n=21+20) geomean 465.2Mi 583.4Mi +25.40% MFC after: 1 month MFC to: stable/15 Approved by: mhorne, markj (mentor) Reviewed by: fuz Sponsored by: Google LLC (GSoC 2024) Differential Revision: https://reviews.freebsd.org/D45693 --- lib/libc/riscv/string/Makefile.inc | 1 + lib/libc/riscv/string/strlen.S | 77 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 78 insertions(+) diff --git a/lib/libc/riscv/string/Makefile.inc b/lib/libc/riscv/string/Makefile.inc index 44aeb65bf1f7..5853ea114277 100644 --- a/lib/libc/riscv/string/Makefile.inc +++ b/lib/libc/riscv/string/Makefile.inc @@ -1,4 +1,5 @@ MDSRCS+= \ memchr.S \ memset.S \ + strlen.S \ strrchr.S diff --git a/lib/libc/riscv/string/strlen.S b/lib/libc/riscv/string/strlen.S new file mode 100644 index 000000000000..3beb160f2e6f --- /dev/null +++ b/lib/libc/riscv/string/strlen.S @@ -0,0 +1,77 @@ +/*- + * SPDX-License-Identifier: BSD-2-Clause + * + * Copyright (c) 2024 Strahinja Stanisic + */ + +#include + +/* + * https://graphics.stanford.edu/~seander/bithacks.html#ZeroInWord + * uses haszero(v) (((v) - 0x01010101UL) & ~(v) & 0x80808080UL) + * which evalutates > 0 when there is zero in v + * + * register a0 - char *s + */ +ENTRY(strlen) + /* + * register a0 - char *str_start + * register a1 - char *str_ptr + * register a2 - char[8] iter + */ + + /* load constants for haszero */ + li t0, 0x0101010101010101 + slli t1, t0, 7 # 0x8080808080808080, avoid li + + /* check alignment of str_start */ + andi a1, a0, ~0b111 + ld a2, (a1) + beq a1, a0, .Lhas_zero + + /* fill bytes before str_start with non-zero */ + slli t2, a0, 3 + addi t3, t2, -64 + neg t3, t3 + srl t3, t0, t3 + or a2, a2, t3 + + /* unrolled iteration of haszero */ + not t2, a2 + sub a2, a2, t0 + and a2, a2, t2 + and a2, a2, t1 + + bnez a2, .Lfind_zero + +.Lloop_has_zero: + ld a2, 8(a1) + addi a1, a1, 8 # move ptr to next 8byte +.Lhas_zero: + not t2, a2 + sub a2, a2, t0 + and a2, a2, t2 + and a2, a2, t1 + + beqz a2, .Lloop_has_zero + +.Lfind_zero: + /* use (iter & -iter) to isolate lowest set bit */ + sub a3, zero, a2 #a3 = -iter + and t1, a2, a3 #t1 = (iter & -iter) + + li t0, 0x0001020304050607 + srli t1, t1, 7 + /* + * lowest set bit is 2^(8*k) + * multiplying by it shifts the idx array in t0 by k bytes to the left + */ + mul t1, t1, t0 + /* highest byte contains idx of first zero */ + srli t1, t1, 56 + + add a1, a1, t1 + sub a0, a1, a0 + ret +END(strlen) +