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([71.212.142.33]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-83f19c5be71sm9670317b3a.39.2026.05.16.17.26.06 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 16 May 2026 17:26:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1778977567; x=1779582367; darn=nongnu.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:to:from:from:to:cc:subject:date:message-id :reply-to; bh=AsQJRNP1GjT+LK7oBczLFbhTenBiS0j96dQXCFfIHLw=; b=g2wxqbULpeIgdIwlInPZKwXlxtz1wJJ56vV+ioGCAPQqIDzUUk+cCWl7kFUwch4aGG YMCrGSn238rT39QkWMDpLfTuSVRECX8kStnQSvdMOX/j7ujx0Q/X8lOzvVPmi9sXQ6U6 bI2PfojZuAF9OelOk9MwuBzuTRUkPuXDWT1k0IpDRZ0wKi9svrHC7KPVqzDzDLrTnKIL uZCmlwbjsN6u7X9TYRYXbhCM168nvshgrNh25B8D6dUvd+ks1EFcs5izxUQ/laSi51pC SgjQY8vWpBc+b1jJE5sfKjMmnasJ5ITO+2IVgL/dGG26PloyqHNgCu6joqrFmI27KM5Y eHZg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1778977567; x=1779582367; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:to:from:x-gm-gg:x-gm-message-state:from:to :cc:subject:date:message-id:reply-to; bh=AsQJRNP1GjT+LK7oBczLFbhTenBiS0j96dQXCFfIHLw=; b=FeC+9AjSLiRdCxYnAuUTL1B+6ZNi6qs4Ilyla6Hczb1H/iarSdUk7IOupUPymIQbbQ 39kl4jMhRa8disdmk/OrKI8A5x+BHaK3JVWPcXXXgF6Ekt8T41uHN/DbSl5oE2IBzeSZ gotlMOVV6uZSDOUaZ2x8g6d6lNu8rS23sFAFKVfx30UwwckFSMRBwfxXVJw6VmnZ39B6 pS0/dBbeqkr635AqSAsLGh8pI5CRN+r/oNiccPbWGMjikSKuEbg5DDIv/lJY6gugRgYi T5qKR9Sva4G+EihU3qBLtZVeoRek25RAnJknzR3gRfZW+EPTUOk1xc8I+ugsggio3aZH 44qw== X-Gm-Message-State: AOJu0YzCz8Kb4b7JGEKbqs5QmhMByUU2rTEXmdSnDepMKYcmcaF2KHW0 CoMpCTATGg8ofawqOq3IVrzyt4fDvPgFxLO/KjArt+Tv/kJ6rh6O/QnPXhQtdZYDhancwYUWefM btnPv X-Gm-Gg: Acq92OFc8hVA25r8vdCt7ydBiX8xdWhDANvf4YQQxXR1qTAmZecFmRnGJDfY3eA/JtU jLCPq71ahBngcNd+XseBSBFxWhJYTNg3zIBzL/dkWcMHEqLvCIJ+Nc97aDubkHDC/4rZmil9keH mAYIquXqR3d32I3Sp+q/Ryt3ul2wDRtsZq3z/hwDW178lj9pa69SwVsg1KBmFlpxT2PYVa50eq2 fK+tjo8nMMXCo4A1qg2BoGWfdv2AL6zH7+dnPgbz1+Hc5AK1owFP44GQ+KTkZPxRmVmwV0+q5Y5 +ejijX5Xt3TV7sqPr8AWG0rdz0ZvAIDQZoiTKIvwWVH3UT4zNRasNLhdyBNRfw/7VFYZnE7KGfG ZrXO9VxstmOT1c/VOQl0UdVv0FJFWn0fuGQAf9GshPsdh8Rf4JR95jeH4BbUVgS0Z0O1kDrc6iS a46RlT+7MRynVdA3EXd0upS9qYIHpK X-Received: by 2002:a05:6a00:429b:b0:83e:b125:ff30 with SMTP id d2e1a72fcca58-83f33ab698bmr10169419b3a.7.1778977566951; Sat, 16 May 2026 17:26:06 -0700 (PDT) From: Richard Henderson To: qemu-devel@nongnu.org Subject: [PATCH v4 12/12] fpu: Introduce exp_scalbn Date: Sat, 16 May 2026 17:25:49 -0700 Message-ID: <20260517002550.321291-13-richard.henderson@linaro.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260517002550.321291-1-richard.henderson@linaro.org> References: <20260517002550.321291-1-richard.henderson@linaro.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable 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=lists1p.gnu.org; Received-SPF: pass client-ip=2607:f8b0:4864:20::52f; envelope-from=richard.henderson@linaro.org; helo=mail-pg1-x52f.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @linaro.org) X-ZM-MESSAGEID: 1778977630948158500 Content-Type: text/plain; charset="utf-8" Avoid exponent overflow as well as checking that we don't lose information with opposing scaling. Use it in partsN(scalbn) and partsN(round_to_int_normal). Signed-off-by: Richard Henderson Reviewed-by: Philippe Mathieu-Daud=C3=A9 --- fpu/softfloat.c | 17 +++++++++++++++++ fpu/softfloat-parts.c.inc | 5 ++--- 2 files changed, 19 insertions(+), 3 deletions(-) diff --git a/fpu/softfloat.c b/fpu/softfloat.c index a762f4b43a..722bf5ecda 100644 --- a/fpu/softfloat.c +++ b/fpu/softfloat.c @@ -601,6 +601,23 @@ static float128 QEMU_FLATTEN float128_pack_raw(const F= loatParts128 *p) *-------------------------------------------------------------------------= ---*/ #include "softfloat-specialize.c.inc" =20 +static int32_t exp_scalbn(int32_t exp, int32_t scale) +{ + /* + * Catch chains of scaling which lose information. + * In particular, if the exponent has been saturated, + * do not allow it to become unsaturated. + */ + if (unlikely(exp =3D=3D INT32_MAX)) { + assert(scale >=3D 0); + } else if (unlikely(exp =3D=3D INT32_MIN)) { + assert(scale <=3D 0); + } else { + exp =3D sadd32_saturate(exp, scale); + } + return exp; +} + /* * Helper functions for softfloat-parts.c.inc, per-size operations. */ diff --git a/fpu/softfloat-parts.c.inc b/fpu/softfloat-parts.c.inc index 914e588ec8..0c617beef7 100644 --- a/fpu/softfloat-parts.c.inc +++ b/fpu/softfloat-parts.c.inc @@ -1108,8 +1108,7 @@ static bool partsN(round_to_int_normal)(FloatPartsN *= a, FloatRoundMode rmode, uint64_t frac_lsb, frac_lsbm1, rnd_even_mask, rnd_mask, inc; int shift_adj; =20 - scale =3D MIN(MAX(scale, -0x10000), 0x10000); - a->exp +=3D scale; + a->exp =3D exp_scalbn(a->exp, scale); =20 if (a->exp < 0) { bool one; @@ -1633,7 +1632,7 @@ FloatPartsN partsN(scalbn)(const FloatPartsN *a, int = n, float_status *s) case float_class_normal: { FloatPartsN r =3D *a; - r.exp +=3D MIN(MAX(n, -0x10000), 0x10000); + r.exp =3D exp_scalbn(r.exp, n); return r; } default: --=20 2.43.0