On Mon, Feb 23, 2026 at 07:21:54PM +1100, Richard Henderson wrote:
> From: Max Chou <max.chou@sifive.com>
>
> Signed-off-by: Max Chou <max.chou@sifive.com>
> [rth: Update for exp_max_kind]
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> include/fpu/softfloat-types.h | 1 +
> include/fpu/softfloat.h | 4 +++-
> fpu/softfloat.c | 26 ++++++++++++++++++++++++++
> 3 files changed, 30 insertions(+), 1 deletion(-)
>
> diff --git a/include/fpu/softfloat-types.h b/include/fpu/softfloat-types.h
> index 9c84a101e5..ead146c22d 100644
> --- a/include/fpu/softfloat-types.h
> +++ b/include/fpu/softfloat-types.h
> @@ -122,6 +122,7 @@ typedef uint16_t bfloat16;
> /*
> * Open Compute Project (OCP) Microscaling Formats
> */
> +typedef uint8_t float4_e2m1;
> typedef uint8_t float8_e4m3;
> typedef uint8_t float8_e5m2;
>
> diff --git a/include/fpu/softfloat.h b/include/fpu/softfloat.h
> index 31d3f76d3f..8389a07b04 100644
> --- a/include/fpu/softfloat.h
> +++ b/include/fpu/softfloat.h
> @@ -190,9 +190,11 @@ float128 uint64_to_float128(uint64_t, float_status *status);
> float128 uint128_to_float128(Int128, float_status *status);
>
> /*----------------------------------------------------------------------------
> -| OCP FP8 conversion routines.
> +| OCP FP{4,8} conversion routines.
> *----------------------------------------------------------------------------*/
>
> +float8_e4m3 float4_e2m1_to_float8_e4m3(float4_e2m1, float_status *status);
> +
> bfloat16 float8_e4m3_to_bfloat16(float8_e4m3, float_status *status);
> float8_e4m3 bfloat16_to_float8_e4m3(bfloat16, bool sat, float_status *status);
> float8_e4m3 float32_to_float8_e4m3(float32, bool sat, float_status *status);
> diff --git a/fpu/softfloat.c b/fpu/softfloat.c
> index 6e21882ab2..91c34307c8 100644
> --- a/fpu/softfloat.c
> +++ b/fpu/softfloat.c
> @@ -574,6 +574,11 @@ typedef struct {
> .frac_shift = (-F - 1) & 63, \
> .round_mask = (1ull << ((-F - 1) & 63)) - 1
>
> +static const FloatFmt float4_e2m1_params = {
> + FLOAT_PARAMS(2, 1),
> + .exp_max_kind = float_expmax_normal,
> +};
> +
> static const FloatFmt float8_e4m3_params = {
> FLOAT_PARAMS(4, 3),
> .exp_max_kind = float_expmax_e4m3
> @@ -641,6 +646,11 @@ static void unpack_raw64(FloatParts64 *r, const FloatFmt *fmt, uint64_t raw)
> };
> }
>
> +static void QEMU_FLATTEN float4_e2m1_unpack_raw(FloatParts64 *p, float4_e2m1 f)
> +{
> + unpack_raw64(p, &float4_e2m1_params, f);
> +}
> +
> static void QEMU_FLATTEN float8_e4m3_unpack_raw(FloatParts64 *p, float8_e4m3 f)
> {
> unpack_raw64(p, &float8_e4m3_params, f);
> @@ -1709,6 +1719,13 @@ static const uint16_t rsqrt_tab[128] = {
> * Pack/unpack routines with a specific FloatFmt.
> */
>
> +static void float4_e2m1_unpack_canonical(FloatParts64 *p, float4_e2m1 f,
> + float_status *s)
> +{
> + float4_e2m1_unpack_raw(p, f);
> + parts_canonicalize(p, s, &float4_e2m1_params);
> +}
> +
> static void float8_e4m3_unpack_canonical(FloatParts64 *p, float8_e4m3 f,
> float_status *s)
> {
> @@ -2929,6 +2946,15 @@ static void parts_float_to_float_widen(FloatParts128 *a, FloatParts64 *b,
> }
> }
>
> +float8_e4m3 float4_e2m1_to_float8_e4m3(float4_e2m1 a, float_status *s)
> +{
> + FloatParts64 p;
> +
> + float4_e2m1_unpack_canonical(&p, a, s);
> + parts_float_to_float(&p, s);
> + return float8_e4m3_round_pack_canonical(&p, s, false);
> +}
> +
> bfloat16 float8_e4m3_to_bfloat16(float8_e4m3 a, float_status *s)
> {
> FloatParts64 p;
> --
> 2.43.0
>
Reviewed-by: Chao Liu <chao.liu.zevorn@gmail.com>
Thanks,
Chao