From nobody Sat Aug 9 20:14:11 2025 X-Original-To: dev-commits-src-main@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 4bzsYc4YhXz64JQ4; Sat, 09 Aug 2025 20:14:12 +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 "R10" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4bzsYc0Wgcz3Bw8; Sat, 09 Aug 2025 20:14:12 +0000 (UTC) (envelope-from git@FreeBSD.org) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1754770452; 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=8M6C5Fv9iA3fn/gesKkRhGuvkaWjXyIYTh4wNLfUxTI=; b=RFypWUOkbikLh9DvNYsFQ/rbDjDzSeKruGzLP8hYfvcpR+DhJuW3keAGAyK2QQ09fWla7Q xCTD3/Ny+xZe6UBxcaiuVf5irScb9sNv1uDrA8Os9fE+u3qO/pX3nWABcPBoCjP+SEVhsC MLoqUlarhLIRWV/MaN6knlG/dhFCDkfzT5mF5LRCXnQs/I3s+XW+ikBl/Oh1QOGvCRlC/s YbSN8mp1yh+oTV0Y9gRApKsVmaOvu/fL6TMDwKzBDPNnN8dhkRSSNJONns/3hLJV3u1PXF 1wX7kr5VQJ0CE3EAAxekXVVbDCrz95kyS3g3SXbGO7rO24/c/WMSkeI/mvdjOg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1754770452; 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=8M6C5Fv9iA3fn/gesKkRhGuvkaWjXyIYTh4wNLfUxTI=; b=Xn1sMUW084Ytv6xivy51wDlZfe+7nuZ9/hfNQ4dqQ919kUmUl7W4iurlC6kcXS0w6wvh2W v2giaqrYQ13h03MZ3iAAfWvlyIMeXRussgX5mc3zkJCjKqixLzAF5WkiZx0xsiPidr6V8x BMv5JWFZSJ6YnbKOvTuuM576GZ5+1VZGwRtivPFedakFFIxdOgFfKW5Qn0Egbpj2bIk9sD E9MySJ6eMQwMQ+4A2K1pKdmc68lrajIfaJq/exgg11XmLY900UvTLAV0Ba44bHz4MVA1r2 VC53qWLVTEAJB8Q7fiU8f3wJzo4qS8utSqFLPfqpwL/arTuSwPg3fyxosOYtkQ== ARC-Authentication-Results: i=1; mx1.freebsd.org; none ARC-Seal: i=1; s=dkim; d=freebsd.org; t=1754770452; a=rsa-sha256; cv=none; b=mPJWs/shXfrX8mfRvc6gj2ICiQiwtgZED63ns13zc95mKTgxpeXlgdPWgnbA6XESISFvfl XkqV9LbJtSpwwNscU6rWmtVThDyICnBcQ3H9FXJl/3frwamY7SqfpwE9PX+u7YGzVuewn8 jglcDfRAnuSkGqnXgQ9hU1iseRe6V7W9M7sitBYbEf0LXh026FbtKc3iXih5l6kWvEI8to TyO56Abyfu464N9BWfuvkT1oNSj1FLKdc863aI4jN/7w86XC3dAK4uepjoooeAgfwMOsGR wpbqA39KJcQk1t736I6ctUwQimRPj4C7hFont73S1n54s+smBP0+D5npstXdvA== 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 4bzsYb6cN6zcC4; Sat, 09 Aug 2025 20:14:11 +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 579KEBsU086195; Sat, 9 Aug 2025 20:14:11 GMT (envelope-from git@gitrepo.freebsd.org) Received: (from git@localhost) by gitrepo.freebsd.org (8.18.1/8.18.1/Submit) id 579KEBuH086192; Sat, 9 Aug 2025 20:14:11 GMT (envelope-from git) Date: Sat, 9 Aug 2025 20:14:11 GMT Message-Id: <202508092014.579KEBuH086192@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: 30acc8427026 - main - libc/amd64: rewrite memrchr() scalar impl. to read the string from the back List-Id: Commit messages for the main branch of the src repository List-Archive: https://lists.freebsd.org/archives/dev-commits-src-main List-Help: List-Post: List-Subscribe: List-Unsubscribe: X-BeenThere: dev-commits-src-main@freebsd.org Sender: owner-dev-commits-src-main@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: 30acc84270266e41f66cf572f67c3290d923da2f Auto-Submitted: auto-generated The branch main has been updated by fuz: URL: https://cgit.FreeBSD.org/src/commit/?id=30acc84270266e41f66cf572f67c3290d923da2f commit 30acc84270266e41f66cf572f67c3290d923da2f Author: Robert Clausecker AuthorDate: 2025-07-29 20:12:11 +0000 Commit: Robert Clausecker CommitDate: 2025-08-09 20:13:27 +0000 libc/amd64: rewrite memrchr() scalar impl. to read the string from the back A very simple implementation as I don't have the patience right now to write a full SWAR kernel. Should still do the trick if you wish to opt out of SSE for some reason. Reported by: Mikael Simonsson Reviewed by: strajabot PR: 288321 MFC after: 1 month --- lib/libc/amd64/string/memrchr.S | 72 +++++++++++++++++++---------------------- 1 file changed, 34 insertions(+), 38 deletions(-) diff --git a/lib/libc/amd64/string/memrchr.S b/lib/libc/amd64/string/memrchr.S index f1ba48d6bb41..80fb306af2a3 100644 --- a/lib/libc/amd64/string/memrchr.S +++ b/lib/libc/amd64/string/memrchr.S @@ -16,58 +16,54 @@ ARCHFUNCS(memrchr) ENDARCHFUNCS(memrchr) ARCHENTRY(memrchr, scalar) - xor %eax, %eax # prospective return value - sub $4, %rdx # 4 bytes left to process? - jb 1f + lea -1(%rdi, %rdx, 1), %rax # point to last char in buffer + sub $4, %rdx # 4 bytes left to process? + jb .Ltail ALIGN_TEXT -0: xor %r8, %r8 - lea 2(%rdi), %r10 - cmp %sil, 2(%rdi) - cmovne %r8, %r10 # point to null if no match +0: cmp %sil, (%rax) # match at last entry? + je 1f - cmp %sil, (%rdi) - cmove %rdi, %r8 # point to first char if match + cmp %sil, -1(%rax) # match at second to last entry? + je 2f - lea 1(%rdi), %r9 - cmp %sil, 1(%rdi) - cmovne %r8, %r9 # point to first result if no match in second + cmp %sil, -2(%rax) # match at third to last entry? + je 3f - lea 3(%rdi), %r11 - cmp %sil, 3(%rdi) - cmovne %r10, %r11 + cmp %sil, -3(%rax) # match at fourth to last entry? + je 4f - test %r11, %r11 - cmovz %r9, %r11 # take first pair match if none in second + sub $4, %rax + sub $4, %rdx + jae 0b - test %r11, %r11 - cmovnz %r11, %rax # take match in current set if any +.Ltail: cmp $-3, %edx # at least one character left to process? + jb .Lnotfound - add $4, %rdi - sub $4, %rdx - jae 0b + cmp %sil, (%rax) + je 1f -1: cmp $-3, %edx # a least one character left to process? - jb 2f + cmp $-2, %edx # at least two characters left to process? + jb .Lnotfound - cmp %sil, (%rdi) - cmove %rdi, %rax + cmp %sil, -1(%rax) + je 2f - lea 1(%rdi), %rcx - cmp $-2, %edx # at least two characters left to process? - jb 2f + cmp $-1, %edx # at least three characters left to process? + jb .Lnotfound - cmp %sil, 1(%rdi) - cmove %rcx, %rax + cmp %sil, -2(%rax) + je 3f - lea 2(%rdi), %rcx - cmp $-1, %edx # at least three character left to process? - jb 2f - - cmp %sil, 2(%rdi) - cmove %rcx, %rax +.Lnotfound: + xor %eax, %eax + ret -2: ret + /* match found -- adjust rax to point to matching byte */ +4: dec %rax +3: dec %rax +2: dec %rax +1: ret ARCHEND(memrchr, scalar) ARCHENTRY(memrchr, baseline)