From nobody Mon Oct 06 19:21:39 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 4cgTfC4pzpz6BQD7; Mon, 06 Oct 2025 19:21:39 +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 4cgTfC4GFPz3Blq; Mon, 06 Oct 2025 19:21:39 +0000 (UTC) (envelope-from git@FreeBSD.org) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1759778499; 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=ps7aF0MH3Ji0MLMboVoJvjlSV5RaicnWxa6e/Qeu7Rg=; b=yhEochXv38Myyxtc/mOeqS658FitjblI7ITuBbutosq9MITlTTzHs2TrdJwv9t0bCyrZ84 KYKfEob4jkPN+oQMlQvrcuT6X68HAoKwbPJYiX9pLOybdWBTcditMwqu4n/L7l7+9qUiW0 2+ejQXTRds4nVuujiToksiErHYMZZNTfWI+wrq7L0GAQSgirmB3wOfUUKmXXulyFTx1XZN hLtZsHbUDrBALFrjtLdPoTyKkh0+DbZd/oP2TDqpkl84aVe04J5O/FfajxEjSKx89WzVvu 3Wgifpc98/HB73FiWEkFUQjxd3D1zIpAckGtCfqdPZ0WJ8wtm70nzwIJ+Cnfig== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1759778499; 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=ps7aF0MH3Ji0MLMboVoJvjlSV5RaicnWxa6e/Qeu7Rg=; b=LIMt4JetmjLaDXbF3E3k38fJmg4EPD1H77y4fbjodEdY7tqlSxu3xFSsfb44ASXz0ImyKf dcER4ch+2S3X+0VRgeihZ1X8tunl1QlZnkxkDb92VTps8UaFje6r2R+O83xVPFJlsleSMa JQKeewE1JHGKCONP2OH4Mc9W49WSNNlc6pUK4kHPPMyr4K2N8pnykm4qHL+alrwO7MQr4L 0v5cUeMH4Em/PrEM/dmSSF7y4Vxmlj5qPS4srVwjgGKAlYpekP+5aDH2/M9rVv6kbCvLPQ 0zw7pcYj7Pi5jCFcyWuHSDbcwMN1PaaL7PghOGM9TMfVs0pYd4t9pyKbkRRrGA== ARC-Seal: i=1; s=dkim; d=freebsd.org; t=1759778499; a=rsa-sha256; cv=none; b=C1pvFYnfn5EUrHi2yRTRNmBIPGGWR0CKpCqTvUx8KKdbjWbjobkTbEeAiAgSd2urOUoKYg JhgWUtbVPuv7OtdaYVo61BCxtblkLqIoD5vBOr6DtSV+6y+AkXhx77FmhL0sHOmWOHnN9u 69m/EBdOJDWuLs2PGyyDVvR3yHsI+tMjxlp+RJE1yr6jgGM8tWRumydarq9Ev1B4kRdMKQ Np1dpxLP5XodGcD2LFjQyWFpbf5FR914B23/NZOaV9di1Fo9hNiZBGAJGnno1hH5akAMn9 /fJS8vgLcM9KwbBLltXtTi4A7mO1O2psBTG/jNnldDgOky0R5jMLl5ivLHQ8iQ== 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 4cgTfC3slqz1BN0; Mon, 06 Oct 2025 19:21:39 +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 596JLd4k092990; Mon, 6 Oct 2025 19:21:39 GMT (envelope-from git@gitrepo.freebsd.org) Received: (from git@localhost) by gitrepo.freebsd.org (8.18.1/8.18.1/Submit) id 596JLdmZ092987; Mon, 6 Oct 2025 19:21:39 GMT (envelope-from git) Date: Mon, 6 Oct 2025 19:21:39 GMT Message-Id: <202510061921.596JLdmZ092987@gitrepo.freebsd.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org From: Mark Johnston Subject: git: 2ba20004ef76 - main - libc: Reimplement the *rand48 family of functions 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: markj X-Git-Repository: src X-Git-Refname: refs/heads/main X-Git-Reftype: branch X-Git-Commit: 2ba20004ef7649db7654520e8376927c4410d9c3 Auto-Submitted: auto-generated The branch main has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=2ba20004ef7649db7654520e8376927c4410d9c3 commit 2ba20004ef7649db7654520e8376927c4410d9c3 Author: Mark Johnston AuthorDate: 2025-09-04 19:34:17 +0000 Commit: Mark Johnston CommitDate: 2025-10-06 19:20:39 +0000 libc: Reimplement the *rand48 family of functions Rather than implementing the recurrence using 3 16-bit integers, as was done in _dorand48() before this patch, provide an equivalent implementation using 64-bit integers. For drand48() and erand48(), replace the use of ldexp() with bit-twiddling assuming IEEE 754 double-precision float layout. This implementation is significantly faster and requires less code, while producing identical outputs on supported platforms. While here, add a STANDARDS section to rand48.3. Obtained from: https://github.com/apple-oss-distributions/libc MFC after: 3 weeks Sponsored by: Klara, Inc. Differential Revision: https://reviews.freebsd.org/D52429 --- lib/libc/gen/_rand48.c | 34 +++------------------------- lib/libc/gen/drand48.c | 6 ++--- lib/libc/gen/erand48.c | 9 ++++---- lib/libc/gen/jrand48.c | 7 +++--- lib/libc/gen/lcong48.c | 12 ++-------- lib/libc/gen/lrand48.c | 6 ++--- lib/libc/gen/mrand48.c | 8 ++----- lib/libc/gen/nrand48.c | 6 +++-- lib/libc/gen/rand48.3 | 5 ++++- lib/libc/gen/rand48.h | 61 +++++++++++++++++++++++++++++++++++++++++++++++++- lib/libc/gen/seed48.c | 18 ++++----------- lib/libc/gen/srand48.c | 13 +++-------- 12 files changed, 95 insertions(+), 90 deletions(-) diff --git a/lib/libc/gen/_rand48.c b/lib/libc/gen/_rand48.c index 990e2c86949b..114c1595b33d 100644 --- a/lib/libc/gen/_rand48.c +++ b/lib/libc/gen/_rand48.c @@ -13,34 +13,6 @@ #include "rand48.h" -unsigned short _rand48_seed[3] = { - RAND48_SEED_0, - RAND48_SEED_1, - RAND48_SEED_2 -}; -unsigned short _rand48_mult[3] = { - RAND48_MULT_0, - RAND48_MULT_1, - RAND48_MULT_2 -}; -unsigned short _rand48_add = RAND48_ADD; - -void -_dorand48(unsigned short xseed[3]) -{ - unsigned long accu; - unsigned short temp[2]; - - accu = (unsigned long) _rand48_mult[0] * (unsigned long) xseed[0] + - (unsigned long) _rand48_add; - temp[0] = (unsigned short) accu; /* lower 16 bits */ - accu >>= sizeof(unsigned short) * 8; - accu += (unsigned long) _rand48_mult[0] * (unsigned long) xseed[1] + - (unsigned long) _rand48_mult[1] * (unsigned long) xseed[0]; - temp[1] = (unsigned short) accu; /* middle 16 bits */ - accu >>= sizeof(unsigned short) * 8; - accu += _rand48_mult[0] * xseed[2] + _rand48_mult[1] * xseed[1] + _rand48_mult[2] * xseed[0]; - xseed[0] = temp[0]; - xseed[1] = temp[1]; - xseed[2] = (unsigned short) accu; -} +uint48 _rand48_seed = RAND48_SEED; +uint48 _rand48_mult = RAND48_MULT; +uint48 _rand48_add = RAND48_ADD; diff --git a/lib/libc/gen/drand48.c b/lib/libc/gen/drand48.c index cec04a6a2425..f7f43ff20468 100644 --- a/lib/libc/gen/drand48.c +++ b/lib/libc/gen/drand48.c @@ -13,10 +13,10 @@ #include "rand48.h" -extern unsigned short _rand48_seed[3]; - double drand48(void) { - return erand48(_rand48_seed); + ERAND48_BEGIN; + _DORAND48(_rand48_seed); + ERAND48_END(_rand48_seed); } diff --git a/lib/libc/gen/erand48.c b/lib/libc/gen/erand48.c index 286904c27839..38d4774a9fe6 100644 --- a/lib/libc/gen/erand48.c +++ b/lib/libc/gen/erand48.c @@ -16,8 +16,9 @@ double erand48(unsigned short xseed[3]) { - _dorand48(xseed); - return ldexp((double) xseed[0], -48) + - ldexp((double) xseed[1], -32) + - ldexp((double) xseed[2], -16); + uint48 tmp; + + ERAND48_BEGIN; + DORAND48(tmp, xseed); + ERAND48_END(tmp); } diff --git a/lib/libc/gen/jrand48.c b/lib/libc/gen/jrand48.c index 0a9f780a9e5c..93442439d49e 100644 --- a/lib/libc/gen/jrand48.c +++ b/lib/libc/gen/jrand48.c @@ -11,14 +11,13 @@ * to anyone/anything when using this software. */ -#include - #include "rand48.h" long jrand48(unsigned short xseed[3]) { + uint48 tmp; - _dorand48(xseed); - return ((int32_t)(((uint32_t)xseed[2] << 16) | (uint32_t)xseed[1])); + DORAND48(tmp, xseed); + return ((int)((tmp >> 16) & 0xffffffff)); } diff --git a/lib/libc/gen/lcong48.c b/lib/libc/gen/lcong48.c index f13826b3d3f3..871b2110ed94 100644 --- a/lib/libc/gen/lcong48.c +++ b/lib/libc/gen/lcong48.c @@ -13,18 +13,10 @@ #include "rand48.h" -extern unsigned short _rand48_seed[3]; -extern unsigned short _rand48_mult[3]; -extern unsigned short _rand48_add; - void lcong48(unsigned short p[7]) { - _rand48_seed[0] = p[0]; - _rand48_seed[1] = p[1]; - _rand48_seed[2] = p[2]; - _rand48_mult[0] = p[3]; - _rand48_mult[1] = p[4]; - _rand48_mult[2] = p[5]; + LOADRAND48(_rand48_seed, &p[0]); + LOADRAND48(_rand48_mult, &p[3]); _rand48_add = p[6]; } diff --git a/lib/libc/gen/lrand48.c b/lib/libc/gen/lrand48.c index a3d0111cf4d5..cc07044b8af9 100644 --- a/lib/libc/gen/lrand48.c +++ b/lib/libc/gen/lrand48.c @@ -13,11 +13,9 @@ #include "rand48.h" -extern unsigned short _rand48_seed[3]; - long lrand48(void) { - _dorand48(_rand48_seed); - return ((long) _rand48_seed[2] << 15) + ((long) _rand48_seed[1] >> 1); + _DORAND48(_rand48_seed); + return (_rand48_seed >> 17) & 0x7fffffff; } diff --git a/lib/libc/gen/mrand48.c b/lib/libc/gen/mrand48.c index 15b0bfb1bd6e..f9128a6d4188 100644 --- a/lib/libc/gen/mrand48.c +++ b/lib/libc/gen/mrand48.c @@ -15,13 +15,9 @@ #include "rand48.h" -extern unsigned short _rand48_seed[3]; - long mrand48(void) { - - _dorand48(_rand48_seed); - return ((int32_t)(((uint32_t)_rand48_seed[2] << 16) | - (uint32_t)_rand48_seed[1])); + _DORAND48(_rand48_seed); + return ((int)((_rand48_seed >> 16) & 0xffffffff)); } diff --git a/lib/libc/gen/nrand48.c b/lib/libc/gen/nrand48.c index 6c54065e7e0f..f6f4e231105c 100644 --- a/lib/libc/gen/nrand48.c +++ b/lib/libc/gen/nrand48.c @@ -16,6 +16,8 @@ long nrand48(unsigned short xseed[3]) { - _dorand48(xseed); - return ((long) xseed[2] << 15) + ((long) xseed[1] >> 1); + uint48 tmp; + + DORAND48(tmp, xseed); + return ((tmp >> 17) & 0x7fffffff); } diff --git a/lib/libc/gen/rand48.3 b/lib/libc/gen/rand48.3 index 1e47c843058e..3ea649354270 100644 --- a/lib/libc/gen/rand48.3 +++ b/lib/libc/gen/rand48.3 @@ -9,7 +9,7 @@ .\" of any kind. I shall in no event be liable for anything that happens .\" to anyone/anything when using this software. .\" -.Dd September 4, 2012 +.Dd September 11, 2025 .Dt RAND48 3 .Os .Sh NAME @@ -183,5 +183,8 @@ generator calls. .Xr arc4random 3 , .Xr rand 3 , .Xr random 3 +.Sh STANDARDS +The functions described in this page are expected to conform to +.St -p1003.1-2008 . .Sh AUTHORS .An Martin Birgmeier diff --git a/lib/libc/gen/rand48.h b/lib/libc/gen/rand48.h index 9861e99683cb..d3326e851491 100644 --- a/lib/libc/gen/rand48.h +++ b/lib/libc/gen/rand48.h @@ -14,10 +14,11 @@ #ifndef _RAND48_H_ #define _RAND48_H_ +#include #include #include -void _dorand48(unsigned short[3]); +#include "fpmath.h" #define RAND48_SEED_0 (0x330e) #define RAND48_SEED_1 (0xabcd) @@ -27,4 +28,62 @@ void _dorand48(unsigned short[3]); #define RAND48_MULT_2 (0x0005) #define RAND48_ADD (0x000b) +typedef uint64_t uint48; + +extern uint48 _rand48_seed; +extern uint48 _rand48_mult; +extern uint48 _rand48_add; + +#define TOUINT48(x, y, z) \ + ((uint48)(x) + (((uint48)(y)) << 16) + (((uint48)(z)) << 32)) + +#define RAND48_SEED TOUINT48(RAND48_SEED_0, RAND48_SEED_1, RAND48_SEED_2) +#define RAND48_MULT TOUINT48(RAND48_MULT_0, RAND48_MULT_1, RAND48_MULT_2) + +#define LOADRAND48(l, x) do { \ + (l) = TOUINT48((x)[0], (x)[1], (x)[2]); \ +} while (0) + +#define STORERAND48(l, x) do { \ + (x)[0] = (unsigned short)(l); \ + (x)[1] = (unsigned short)((l) >> 16); \ + (x)[2] = (unsigned short)((l) >> 32); \ +} while (0) + +#define _DORAND48(l) do { \ + (l) = (l) * _rand48_mult + _rand48_add; \ +} while (0) + +#define DORAND48(l, x) do { \ + LOADRAND48(l, x); \ + _DORAND48(l); \ + STORERAND48(l, x); \ +} while (0) + +#define ERAND48_BEGIN \ + union { \ + union IEEEd2bits ieee; \ + uint64_t u64; \ + } u; \ + int s + +/* + * Optimization for speed: assume doubles are IEEE 754 and use bit fiddling + * rather than converting to double. Specifically, clamp the result to 48 bits + * and convert to a double in [0.0, 1.0) via division by 2^48. Normalize by + * shifting the most significant bit into the implicit one position and + * adjusting the exponent accordingly. The store to the exponent field + * overwrites the implicit one. + */ +#define ERAND48_END(x) do { \ + u.u64 = ((x) & 0xffffffffffffULL); \ + if (u.u64 == 0) \ + return (0.0); \ + u.u64 <<= 5; \ + for (s = 0; !(u.u64 & (1LL << 52)); s++, u.u64 <<= 1) \ + ; \ + u.ieee.bits.exp = 1022 - s; \ + return (u.ieee.d); \ +} while (0) + #endif /* _RAND48_H_ */ diff --git a/lib/libc/gen/seed48.c b/lib/libc/gen/seed48.c index 258c4bac3c9f..f57656ce1121 100644 --- a/lib/libc/gen/seed48.c +++ b/lib/libc/gen/seed48.c @@ -13,24 +13,14 @@ #include "rand48.h" -extern unsigned short _rand48_seed[3]; -extern unsigned short _rand48_mult[3]; -extern unsigned short _rand48_add; - unsigned short * seed48(unsigned short xseed[3]) { static unsigned short sseed[3]; - sseed[0] = _rand48_seed[0]; - sseed[1] = _rand48_seed[1]; - sseed[2] = _rand48_seed[2]; - _rand48_seed[0] = xseed[0]; - _rand48_seed[1] = xseed[1]; - _rand48_seed[2] = xseed[2]; - _rand48_mult[0] = RAND48_MULT_0; - _rand48_mult[1] = RAND48_MULT_1; - _rand48_mult[2] = RAND48_MULT_2; + STORERAND48(_rand48_seed, sseed); + LOADRAND48(_rand48_seed, xseed); + _rand48_mult = RAND48_MULT; _rand48_add = RAND48_ADD; - return sseed; + return (sseed); } diff --git a/lib/libc/gen/srand48.c b/lib/libc/gen/srand48.c index fd369a094c51..4b82ece72db8 100644 --- a/lib/libc/gen/srand48.c +++ b/lib/libc/gen/srand48.c @@ -13,18 +13,11 @@ #include "rand48.h" -extern unsigned short _rand48_seed[3]; -extern unsigned short _rand48_mult[3]; -extern unsigned short _rand48_add; - void srand48(long seed) { - _rand48_seed[0] = RAND48_SEED_0; - _rand48_seed[1] = (unsigned short) seed; - _rand48_seed[2] = (unsigned short) (seed >> 16); - _rand48_mult[0] = RAND48_MULT_0; - _rand48_mult[1] = RAND48_MULT_1; - _rand48_mult[2] = RAND48_MULT_2; + _rand48_seed = TOUINT48(RAND48_SEED_0, (unsigned short)seed, + (unsigned short)(seed >> 16)); + _rand48_mult = RAND48_MULT; _rand48_add = RAND48_ADD; }