From nobody Tue Feb 10 12:59:37 2026 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1635189748393848.3044958571115; Mon, 25 Oct 2021 12:22:28 -0700 (PDT) Received: from localhost ([::1]:49320 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mf5YB-000868-8t for importer@patchew.org; Mon, 25 Oct 2021 15:22:27 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:41590) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mf5OT-0006EI-JW; Mon, 25 Oct 2021 15:12:25 -0400 Received: from [201.28.113.2] (port=19851 helo=outlook.eldorado.org.br) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mf5OQ-0005n6-An; Mon, 25 Oct 2021 15:12:24 -0400 Received: from power9a ([10.10.71.235]) by outlook.eldorado.org.br with Microsoft SMTPSVC(8.5.9600.16384); Mon, 25 Oct 2021 16:12:18 -0300 Received: from eldorado.org.br (unknown [10.10.70.45]) by power9a (Postfix) with ESMTP id 8B518800145; Mon, 25 Oct 2021 16:12:17 -0300 (-03) From: Luis Pires To: qemu-devel@nongnu.org, qemu-ppc@nongnu.org Subject: [PATCH v4 01/19] host-utils: move checks out of divu128/divs128 Date: Mon, 25 Oct 2021 16:11:36 -0300 Message-Id: <20211025191154.350831-2-luis.pires@eldorado.org.br> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20211025191154.350831-1-luis.pires@eldorado.org.br> References: <20211025191154.350831-1-luis.pires@eldorado.org.br> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-OriginalArrivalTime: 25 Oct 2021 19:12:18.0218 (UTC) FILETIME=[3A7C18A0:01D7C9D4] X-Host-Lookup-Failed: Reverse DNS lookup failed for 201.28.113.2 (failed) Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=201.28.113.2; envelope-from=luis.pires@eldorado.org.br; helo=outlook.eldorado.org.br X-Spam_score_int: -10 X-Spam_score: -1.1 X-Spam_bar: - X-Spam_report: (-1.1 / 5.0 requ) BAYES_00=-1.9, PDS_HP_HELO_NORDNS=0.001, RDNS_NONE=0.793, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Luis Pires , richard.henderson@linaro.org, groug@kaod.org, david@gibson.dropbear.id.au Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZM-MESSAGEID: 1635189749167100003 Content-Type: text/plain; charset="utf-8" In preparation for changing the divu128/divs128 implementations to allow for quotients larger than 64 bits, move the div-by-zero and overflow checks to the callers. Signed-off-by: Luis Pires Reviewed-by: Richard Henderson --- include/hw/clock.h | 5 +++-- include/qemu/host-utils.h | 36 +++++++++++++---------------------- target/ppc/int_helper.c | 14 +++++++++----- util/host-utils.c | 40 ++++++++++++++++++--------------------- 4 files changed, 43 insertions(+), 52 deletions(-) diff --git a/include/hw/clock.h b/include/hw/clock.h index 11f67fb970..7443e6c4ab 100644 --- a/include/hw/clock.h +++ b/include/hw/clock.h @@ -324,8 +324,9 @@ static inline uint64_t clock_ns_to_ticks(const Clock *c= lk, uint64_t ns) return 0; } /* - * Ignore divu128() return value as we've caught div-by-zero and don't - * need different behaviour for overflow. + * BUG: when CONFIG_INT128 is not defined, the current implementation = of + * divu128 does not return a valid truncated quotient, so the result w= ill + * be wrong. */ divu128(&lo, &hi, clk->period); return lo; diff --git a/include/qemu/host-utils.h b/include/qemu/host-utils.h index ca9f3f021b..e82e6239af 100644 --- a/include/qemu/host-utils.h +++ b/include/qemu/host-utils.h @@ -52,36 +52,26 @@ static inline uint64_t muldiv64(uint64_t a, uint32_t b,= uint32_t c) return (__int128_t)a * b / c; } =20 -static inline int divu128(uint64_t *plow, uint64_t *phigh, uint64_t diviso= r) -{ - if (divisor =3D=3D 0) { - return 1; - } else { - __uint128_t dividend =3D ((__uint128_t)*phigh << 64) | *plow; - __uint128_t result =3D dividend / divisor; - *plow =3D result; - *phigh =3D dividend % divisor; - return result > UINT64_MAX; - } +static inline void divu128(uint64_t *plow, uint64_t *phigh, uint64_t divis= or) +{ + __uint128_t dividend =3D ((__uint128_t)*phigh << 64) | *plow; + __uint128_t result =3D dividend / divisor; + *plow =3D result; + *phigh =3D dividend % divisor; } =20 -static inline int divs128(int64_t *plow, int64_t *phigh, int64_t divisor) +static inline void divs128(int64_t *plow, int64_t *phigh, int64_t divisor) { - if (divisor =3D=3D 0) { - return 1; - } else { - __int128_t dividend =3D ((__int128_t)*phigh << 64) | (uint64_t)*pl= ow; - __int128_t result =3D dividend / divisor; - *plow =3D result; - *phigh =3D dividend % divisor; - return result !=3D *plow; - } + __int128_t dividend =3D ((__int128_t)*phigh << 64) | (uint64_t)*plow; + __int128_t result =3D dividend / divisor; + *plow =3D result; + *phigh =3D dividend % divisor; } #else void muls64(uint64_t *plow, uint64_t *phigh, int64_t a, int64_t b); void mulu64(uint64_t *plow, uint64_t *phigh, uint64_t a, uint64_t b); -int divu128(uint64_t *plow, uint64_t *phigh, uint64_t divisor); -int divs128(int64_t *plow, int64_t *phigh, int64_t divisor); +void divu128(uint64_t *plow, uint64_t *phigh, uint64_t divisor); +void divs128(int64_t *plow, int64_t *phigh, int64_t divisor); =20 static inline uint64_t muldiv64(uint64_t a, uint32_t b, uint32_t c) { diff --git a/target/ppc/int_helper.c b/target/ppc/int_helper.c index f5dac3aa87..510faf24cf 100644 --- a/target/ppc/int_helper.c +++ b/target/ppc/int_helper.c @@ -104,10 +104,11 @@ uint64_t helper_divdeu(CPUPPCState *env, uint64_t ra,= uint64_t rb, uint32_t oe) uint64_t rt =3D 0; int overflow =3D 0; =20 - overflow =3D divu128(&rt, &ra, rb); - - if (unlikely(overflow)) { + if (unlikely(rb =3D=3D 0 || ra >=3D rb)) { + overflow =3D 1; rt =3D 0; /* Undefined */ + } else { + divu128(&rt, &ra, rb); } =20 if (oe) { @@ -122,10 +123,13 @@ uint64_t helper_divde(CPUPPCState *env, uint64_t rau,= uint64_t rbu, uint32_t oe) int64_t rt =3D 0; int64_t ra =3D (int64_t)rau; int64_t rb =3D (int64_t)rbu; - int overflow =3D divs128(&rt, &ra, rb); + int overflow =3D 0; =20 - if (unlikely(overflow)) { + if (unlikely(rb =3D=3D 0 || uabs64(ra) >=3D uabs64(rb))) { + overflow =3D 1; rt =3D 0; /* Undefined */ + } else { + divs128(&rt, &ra, rb); } =20 if (oe) { diff --git a/util/host-utils.c b/util/host-utils.c index a789a11b46..701a371843 100644 --- a/util/host-utils.c +++ b/util/host-utils.c @@ -86,24 +86,23 @@ void muls64 (uint64_t *plow, uint64_t *phigh, int64_t a= , int64_t b) *phigh =3D rh; } =20 -/* Unsigned 128x64 division. Returns 1 if overflow (divide by zero or */ -/* quotient exceeds 64 bits). Otherwise returns quotient via plow and */ -/* remainder via phigh. */ -int divu128(uint64_t *plow, uint64_t *phigh, uint64_t divisor) +/* + * Unsigned 128-by-64 division. Returns quotient via plow and + * remainder via phigh. + * The result must fit in 64 bits (plow) - otherwise, the result + * is undefined. + * This function will cause a division by zero if passed a zero divisor. + */ +void divu128(uint64_t *plow, uint64_t *phigh, uint64_t divisor) { uint64_t dhi =3D *phigh; uint64_t dlo =3D *plow; unsigned i; uint64_t carry =3D 0; =20 - if (divisor =3D=3D 0) { - return 1; - } else if (dhi =3D=3D 0) { + if (divisor =3D=3D 0 || dhi =3D=3D 0) { *plow =3D dlo / divisor; *phigh =3D dlo % divisor; - return 0; - } else if (dhi >=3D divisor) { - return 1; } else { =20 for (i =3D 0; i < 64; i++) { @@ -120,15 +119,20 @@ int divu128(uint64_t *plow, uint64_t *phigh, uint64_t= divisor) =20 *plow =3D dlo; *phigh =3D dhi; - return 0; } } =20 -int divs128(int64_t *plow, int64_t *phigh, int64_t divisor) +/* + * Signed 128-by-64 division. Returns quotient via plow and + * remainder via phigh. + * The result must fit in 64 bits (plow) - otherwise, the result + * is undefined. + * This function will cause a division by zero if passed a zero divisor. + */ +void divs128(int64_t *plow, int64_t *phigh, int64_t divisor) { int sgn_dvdnd =3D *phigh < 0; int sgn_divsr =3D divisor < 0; - int overflow =3D 0; =20 if (sgn_dvdnd) { *plow =3D ~(*plow); @@ -145,19 +149,11 @@ int divs128(int64_t *plow, int64_t *phigh, int64_t di= visor) divisor =3D 0 - divisor; } =20 - overflow =3D divu128((uint64_t *)plow, (uint64_t *)phigh, (uint64_t)di= visor); + divu128((uint64_t *)plow, (uint64_t *)phigh, (uint64_t)divisor); =20 if (sgn_dvdnd ^ sgn_divsr) { *plow =3D 0 - *plow; } - - if (!overflow) { - if ((*plow < 0) ^ (sgn_dvdnd ^ sgn_divsr)) { - overflow =3D 1; - } - } - - return overflow; } #endif =20 --=20 2.25.1