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Mon, 23 Feb 2026 00:22:29 -0800 (PST) From: Richard Henderson To: qemu-devel@nongnu.org Cc: max.chou@sifive.com, chao.liu.zevorn@gmail.com Subject: [PATCH v5 7/9] fpu: Add conversion routines for OCP FP8 E5M2 Date: Mon, 23 Feb 2026 19:21:52 +1100 Message-ID: <20260223082154.5623-8-richard.henderson@linaro.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260223082154.5623-1-richard.henderson@linaro.org> References: <20260223082154.5623-1-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=lists.gnu.org; Received-SPF: pass client-ip=2607:f8b0:4864:20::62a; envelope-from=richard.henderson@linaro.org; helo=mail-pl1-x62a.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: 1771834996512154100 Content-Type: text/plain; charset="utf-8" From: Max Chou Signed-off-by: Max Chou [rth: Split out of a larger patch] Signed-off-by: Richard Henderson Reviewed-by: Chao Liu --- include/fpu/softfloat-types.h | 5 +++ include/fpu/softfloat.h | 8 ++++ fpu/softfloat.c | 85 +++++++++++++++++++++++++++++++++++ 3 files changed, 98 insertions(+) diff --git a/include/fpu/softfloat-types.h b/include/fpu/softfloat-types.h index 8f82fdfc97..be7e2de6e3 100644 --- a/include/fpu/softfloat-types.h +++ b/include/fpu/softfloat-types.h @@ -119,6 +119,11 @@ typedef struct { */ typedef uint16_t bfloat16; =20 +/* + * Open Compute Project (OCP) Microscaling Formats + */ +typedef uint8_t float8_e5m2; + /* * Software IEC/IEEE floating-point underflow tininess-detection mode. */ diff --git a/include/fpu/softfloat.h b/include/fpu/softfloat.h index 69b9041ef0..4385462992 100644 --- a/include/fpu/softfloat.h +++ b/include/fpu/softfloat.h @@ -189,6 +189,14 @@ float128 int128_to_float128(Int128, float_status *stat= us); float128 uint64_to_float128(uint64_t, float_status *status); float128 uint128_to_float128(Int128, float_status *status); =20 +/*------------------------------------------------------------------------= ---- +| OCP FP8 conversion routines. +*-------------------------------------------------------------------------= ---*/ + +bfloat16 float8_e5m2_to_bfloat16(float8_e5m2, float_status *status); +float8_e5m2 bfloat16_to_float8_e5m2(bfloat16, bool sat, float_status *stat= us); +float8_e5m2 float32_to_float8_e5m2(float32, bool sat, float_status *status= ); + /*------------------------------------------------------------------------= ---- | Software half-precision conversion routines. *-------------------------------------------------------------------------= ---*/ diff --git a/fpu/softfloat.c b/fpu/softfloat.c index b3c4104854..0dc769283d 100644 --- a/fpu/softfloat.c +++ b/fpu/softfloat.c @@ -572,6 +572,10 @@ typedef struct { .frac_shift =3D (-F - 1) & 63, \ .round_mask =3D (1ull << ((-F - 1) & 63)) - 1 =20 +static const FloatFmt float8_e5m2_params =3D { + FLOAT_PARAMS(5, 2) +}; + static const FloatFmt float16_params =3D { FLOAT_PARAMS(5, 10) }; @@ -627,6 +631,11 @@ static void unpack_raw64(FloatParts64 *r, const FloatF= mt *fmt, uint64_t raw) }; } =20 +static void QEMU_FLATTEN float8_e5m2_unpack_raw(FloatParts64 *p, float8_e5= m2 f) +{ + unpack_raw64(p, &float8_e5m2_params, f); +} + static void QEMU_FLATTEN float16_unpack_raw(FloatParts64 *p, float16 f) { unpack_raw64(p, &float16_params, f); @@ -684,6 +693,11 @@ static uint64_t pack_raw64(const FloatParts64 *p, cons= t FloatFmt *fmt) return ret; } =20 +static float8_e5m2 QEMU_FLATTEN float8_e5m2_pack_raw(const FloatParts64 *p) +{ + return pack_raw64(p, &float8_e5m2_params); +} + static float16 QEMU_FLATTEN float16_pack_raw(const FloatParts64 *p) { return make_float16(pack_raw64(p, &float16_params)); @@ -1675,6 +1689,13 @@ static const uint16_t rsqrt_tab[128] =3D { * Pack/unpack routines with a specific FloatFmt. */ =20 +static void float8_e5m2_unpack_canonical(FloatParts64 *p, float8_e5m2 f, + float_status *s) +{ + float8_e5m2_unpack_raw(p, f); + parts_canonicalize(p, s, &float8_e5m2_params); +} + static void float16a_unpack_canonical(FloatParts64 *p, float16 f, float_status *s, const FloatFmt *par= ams) { @@ -1695,6 +1716,14 @@ static void bfloat16_unpack_canonical(FloatParts64 *= p, bfloat16 f, parts_canonicalize(p, s, &bfloat16_params); } =20 +static float8_e5m2 float8_e5m2_round_pack_canonical(FloatParts64 *p, + float_status *s, + bool saturate) +{ + parts_uncanon(p, s, &float8_e5m2_params, saturate); + return float8_e5m2_pack_raw(p); +} + static float16 float16a_round_pack_canonical(FloatParts64 *p, float_status *s, const FloatFmt *params) @@ -2772,6 +2801,35 @@ static void parts_float_to_ahp(FloatParts64 *a, floa= t_status *s) } } =20 +static void parts_float_to_e5m2(FloatParts64 *a, float_status *s, bool sat= urate) +{ + switch (a->cls) { + case float_class_snan: + case float_class_qnan: + parts_return_nan(a, s); + break; + + case float_class_inf: + /* Per OCP, conversion in SATURATE mode bounds Inf to MAX. */ + if (saturate) { + a->cls =3D float_class_normal; + a->exp =3D float8_e5m2_params.exp_max - 1; + a->frac =3D MAKE_64BIT_MASK(float8_e5m2_params.frac_shift, + float8_e5m2_params.frac_size + 1); + } + break; + + case float_class_denormal: + float_raise(float_flag_input_denormal_used, s); + break; + case float_class_normal: + case float_class_zero: + break; + default: + g_assert_not_reached(); + } +} + static void parts64_float_to_float(FloatParts64 *a, float_status *s) { if (is_nan(a->cls)) { @@ -2836,6 +2894,15 @@ static void parts_float_to_float_widen(FloatParts128= *a, FloatParts64 *b, } } =20 +bfloat16 float8_e5m2_to_bfloat16(float8_e5m2 a, float_status *s) +{ + FloatParts64 p; + + float8_e5m2_unpack_canonical(&p, a, s); + parts_float_to_float(&p, s); + return bfloat16_round_pack_canonical(&p, s); +} + float32 float16_to_float32(float16 a, bool ieee, float_status *s) { const FloatFmt *fmt16 =3D ieee ? &float16_params : &float16_params_ahp; @@ -2856,6 +2923,15 @@ float64 float16_to_float64(float16 a, bool ieee, flo= at_status *s) return float64_round_pack_canonical(&p, s); } =20 +float8_e5m2 float32_to_float8_e5m2(float32 a, bool saturate, float_status = *s) +{ + FloatParts64 p; + + float32_unpack_canonical(&p, a, s); + parts_float_to_e5m2(&p, s, saturate); + return float8_e5m2_round_pack_canonical(&p, s, saturate); +} + float16 float32_to_float16(float32 a, bool ieee, float_status *s) { FloatParts64 p; @@ -2923,6 +2999,15 @@ float32 float64_to_float32(float64 a, float_status *= s) return float32_round_pack_canonical(&p, s); } =20 +float8_e5m2 bfloat16_to_float8_e5m2(bfloat16 a, bool saturate, float_statu= s *s) +{ + FloatParts64 p; + + bfloat16_unpack_canonical(&p, a, s); + parts_float_to_e5m2(&p, s, saturate); + return float8_e5m2_round_pack_canonical(&p, s, saturate); +} + float32 bfloat16_to_float32(bfloat16 a, float_status *s) { FloatParts64 p; --=20 2.43.0