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[97.113.2.170]) by smtp.gmail.com with ESMTPSA id y2-v6sm14512457pgp.92.2018.05.14.15.12.38 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 14 May 2018 15:12:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=xMM/6wnUJ8B/UfH6AgnsVWQZAYVhlZ+l678zaVK2h38=; b=RJOvV0rLN3a256X/U6her30qw+7VdMJZO6/23LTYn8zXILaytmUIlfCmkUxrF0S7Gb m4xPVrJvMtQLWCR/lnr6gm+3PUH1tPLwNbltdy4sCqye7ghZEi6U8Ykz4qyrcGJEsmFz I3QDflfnS6rgCu/+gsZw+izlNqjA+TRrqsaz4= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=xMM/6wnUJ8B/UfH6AgnsVWQZAYVhlZ+l678zaVK2h38=; b=FRWu2btsALyVCg8r5hGdEBl6YEfo8c0RyIZnS8jUTeqbQveULjgohci0OE75BXnW+H R79AITsEf3Q3SBQCDg+1iOpjZwNsOBoSwHNEJzVjyKQHeVvmLMBk/e+7tZUpMm/Jw8NX 1h3Yxf80GoZb8N6u0MVfNRG9YNVRQ4EEToPeaa8rBAdelXuLv7dpbTK764CbGXo2nEXO Ie6W6DOPWiAMNLalb88aUOqanlSxsgI/hzLqlpKNg7vTQn/kXPp9K6yQG51JLhAIfCvJ T3dQFjbKzL46v8kizlH/WDcjJhv6G7zr+/Lscf9T606hrhJX8zg/haiV/BYigWwoVmbh BUDg== X-Gm-Message-State: ALKqPwdUGTsgwS8KC/SNh5yjmHlk2JYqawmJ+Yo392phErEErOpXlblS xYjmB4xrLOv0EnHSv2z0lxAhnjCw4u0= X-Google-Smtp-Source: AB8JxZpqsn5quO2Kc6EswB3sS2mznSZZqf5lho/VPYKtM4TEXw0L4JObgBMxaO0fdrl2x/cCyw7OFA== X-Received: by 2002:a65:53ca:: with SMTP id z10-v6mr7726785pgr.413.1526335959580; Mon, 14 May 2018 15:12:39 -0700 (PDT) From: Richard Henderson To: qemu-devel@nongnu.org Date: Mon, 14 May 2018 15:12:04 -0700 Message-Id: <20180514221219.7091-14-richard.henderson@linaro.org> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180514221219.7091-1-richard.henderson@linaro.org> References: <20180514221219.7091-1-richard.henderson@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2607:f8b0:400e:c05::242 Subject: [Qemu-devel] [PATCH v5 13/28] fpu/softfloat: Partial support for ARM Alternative half-precision X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: peter.maydell@linaro.org, alex.bennee@linaro.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) X-ZohoMail: RDKM_2 RSF_0 Z_629925259 SPT_0 From: Alex Benn=C3=A9e For float16 ARM supports an alternative half-precision format which sacrifices the ability to represent NaN/Inf in return for a higher dynamic range. The new FloatFmt flag, arm_althp, is then used to modify the behaviour of canonicalize and round_canonical with respect to representation and exception raising. Usage of this new flag waits until we re-factor float-to-float conversions. Signed-off-by: Alex Benn=C3=A9e Signed-off-by: Richard Henderson Reviewed-by: Peter Maydell --- v3 - squash NaN to 0 if destination is AHP F16 v4 - handle inf -> ahp max in float_to_float not round_canonical - assert no nan and inf for ahp in round_canonical - check ahp before snan in float_to_float v5 - split out canonicalize and round_canonical changes from the rest --- fpu/softfloat.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/fpu/softfloat.c b/fpu/softfloat.c index 41253c6749..55d0d01ec3 100644 --- a/fpu/softfloat.c +++ b/fpu/softfloat.c @@ -220,8 +220,10 @@ typedef struct { * frac_shift: shift to normalise the fraction with DECOMPOSED_BINARY_PO= INT * The following are computed based the size of fraction * frac_lsb: least significant bit of fraction - * fram_lsbm1: the bit bellow the least significant bit (for rounding) + * frac_lsbm1: the bit bellow the least significant bit (for rounding) * round_mask/roundeven_mask: masks used for rounding + * The following optional modifiers are available: + * arm_althp: handle ARM Alternative Half Precision */ typedef struct { int exp_size; @@ -233,6 +235,7 @@ typedef struct { uint64_t frac_lsbm1; uint64_t round_mask; uint64_t roundeven_mask; + bool arm_althp; } FloatFmt; =20 /* Expand fields based on the size of exponent and fraction */ @@ -324,7 +327,7 @@ static inline float64 float64_pack_raw(FloatParts p) static FloatParts canonicalize(FloatParts part, const FloatFmt *parm, float_status *status) { - if (part.exp =3D=3D parm->exp_max) { + if (part.exp =3D=3D parm->exp_max && !parm->arm_althp) { if (part.frac =3D=3D 0) { part.cls =3D float_class_inf; } else { @@ -413,7 +416,15 @@ static FloatParts round_canonical(FloatParts p, float_= status *s, } frac >>=3D frac_shift; =20 - if (unlikely(exp >=3D exp_max)) { + if (parm->arm_althp) { + /* ARM Alt HP eschews Inf and NaN for a wider exponent. */ + if (unlikely(exp > exp_max)) { + /* Overflow. Return the maximum normal. */ + flags =3D float_flag_invalid; + exp =3D exp_max; + frac =3D -1; + } + } else if (unlikely(exp >=3D exp_max)) { flags |=3D float_flag_overflow | float_flag_inexact; if (overflow_norm) { exp =3D exp_max - 1; @@ -464,12 +475,14 @@ static FloatParts round_canonical(FloatParts p, float= _status *s, =20 case float_class_inf: do_inf: + assert(!parm->arm_althp); exp =3D exp_max; frac =3D 0; break; =20 case float_class_qnan: case float_class_snan: + assert(!parm->arm_althp); exp =3D exp_max; frac >>=3D parm->frac_shift; break; --=20 2.17.0