From 0e9030376e1a8eb6d15cb5e69dffa09a6ff16b92 Mon Sep 17 00:00:00 2001 From: Chih-Min Chao Date: Fri, 22 Oct 2021 00:08:45 +0800 Subject: softfloat: add APIs to handle alternative sNaN propagation for fmax/fmin For "fmax/fmin ft0, ft1, ft2" and if one of the inputs is sNaN, The original logic: Return NaN and set invalid flag if ft1 == sNaN || ft2 == sNan. The alternative path: Set invalid flag if ft1 == sNaN || ft2 == sNaN. Return NaN only if ft1 == NaN && ft2 == NaN. The IEEE 754 spec allows both implementation and some architecture such as riscv choose different defintions in two spec versions. (riscv-spec-v2.2 use original version, riscv-spec-20191213 changes to alternative) Signed-off-by: Chih-Min Chao Signed-off-by: Frank Chang Reviewed-by: Richard Henderson Message-Id: <20211021160847.2748577-2-frank.chang@sifive.com> Signed-off-by: Alistair Francis --- fpu/softfloat-parts.c.inc | 25 +++++++++++++++++++++++-- 1 file changed, 23 insertions(+), 2 deletions(-) (limited to 'fpu/softfloat-parts.c.inc') diff --git a/fpu/softfloat-parts.c.inc b/fpu/softfloat-parts.c.inc index dddee92d6e..41d4b17e41 100644 --- a/fpu/softfloat-parts.c.inc +++ b/fpu/softfloat-parts.c.inc @@ -1219,14 +1219,35 @@ static FloatPartsN *partsN(minmax)(FloatPartsN *a, FloatPartsN *b, if (unlikely(ab_mask & float_cmask_anynan)) { /* - * For minnum/maxnum, if one operand is a QNaN, and the other + * For minNum/maxNum (IEEE 754-2008) + * or minimumNumber/maximumNumber (IEEE 754-2019), + * if one operand is a QNaN, and the other * operand is numerical, then return numerical argument. */ - if ((flags & minmax_isnum) + if ((flags & (minmax_isnum | minmax_isnumber)) && !(ab_mask & float_cmask_snan) && (ab_mask & ~float_cmask_qnan)) { return is_nan(a->cls) ? b : a; } + + /* + * In IEEE 754-2019, minNum, maxNum, minNumMag and maxNumMag + * are removed and replaced with minimum, minimumNumber, maximum + * and maximumNumber. + * minimumNumber/maximumNumber behavior for SNaN is changed to: + * If both operands are NaNs, a QNaN is returned. + * If either operand is a SNaN, + * an invalid operation exception is signaled, + * but unless both operands are NaNs, + * the SNaN is otherwise ignored and not converted to a QNaN. + */ + if ((flags & minmax_isnumber) + && (ab_mask & float_cmask_snan) + && (ab_mask & ~float_cmask_anynan)) { + float_raise(float_flag_invalid, s); + return is_nan(a->cls) ? b : a; + } + return parts_pick_nan(a, b, s); } -- cgit v1.2.3