Generalize arm_althp to indicate how exp==max should be handled for the format. Reorganize canonicalize and uncanon_normal to use a switch statement, allowing more cases to be added trivially.
Signed-off-by: Richard Henderson <[email protected]> --- fpu/softfloat.c | 17 ++++++-- fpu/softfloat-parts.c.inc | 92 ++++++++++++++++++++++++--------------- 2 files changed, 69 insertions(+), 40 deletions(-) diff --git a/fpu/softfloat.c b/fpu/softfloat.c index 8094358c2e..18098c4cdd 100644 --- a/fpu/softfloat.c +++ b/fpu/softfloat.c @@ -522,7 +522,16 @@ typedef struct { #define DECOMPOSED_BINARY_POINT 63 #define DECOMPOSED_IMPLICIT_BIT (1ull << DECOMPOSED_BINARY_POINT) -/* Structure holding all of the relevant parameters for a format. +/* Format-specific handling of exp == exp_max */ +typedef enum __attribute__((__packed__)) { + /* exp==max, frac==0 ? infinity : nan; this is ieee standard. */ + float_expmax_ieee, + /* exp==max is a normal number; no infinity or nan representation. */ + float_expmax_normal, +} FloatFmtExpMaxKind; + +/* + * Structure holding all of the relevant parameters for a format. * exp_size: the size of the exponent field * exp_bias: the offset applied to the exponent field * exp_max: the maximum normalised exponent @@ -531,7 +540,7 @@ typedef struct { * The following are computed based the size of fraction * round_mask: bits below lsb which must be rounded * The following optional modifiers are available: - * arm_althp: handle ARM Alternative Half Precision + * exp_max_kind: affects how exp == exp_max is interpreted * has_explicit_bit: has an explicit integer bit; this affects whether * the float_status floatx80_behaviour handling applies */ @@ -542,7 +551,7 @@ typedef struct { int exp_max; int frac_size; int frac_shift; - bool arm_althp; + FloatFmtExpMaxKind exp_max_kind; bool has_explicit_bit; uint64_t round_mask; } FloatFmt; @@ -566,7 +575,7 @@ static const FloatFmt float16_params = { static const FloatFmt float16_params_ahp = { FLOAT_PARAMS(5, 10), - .arm_althp = true + .exp_max_kind = float_expmax_normal, }; static const FloatFmt bfloat16_params = { diff --git a/fpu/softfloat-parts.c.inc b/fpu/softfloat-parts.c.inc index 5e0438fc0b..d3c9c7a913 100644 --- a/fpu/softfloat-parts.c.inc +++ b/fpu/softfloat-parts.c.inc @@ -227,18 +227,30 @@ static void partsN(canonicalize)(FloatPartsN *p, float_status *status, p->exp = fmt->frac_shift - fmt->exp_bias - shift + !has_pseudo_denormals; } - } else if (likely(p->exp < fmt->exp_max) || fmt->arm_althp) { - p->cls = float_class_normal; - p->exp -= fmt->exp_bias; - frac_shl(p, fmt->frac_shift); - p->frac_hi |= DECOMPOSED_IMPLICIT_BIT; - } else if (likely(frac_eqz(p))) { - p->cls = float_class_inf; - } else { - frac_shl(p, fmt->frac_shift); - p->cls = (parts_is_snan_frac(p->frac_hi, status) - ? float_class_snan : float_class_qnan); + return; } + if (unlikely(p->exp == fmt->exp_max)) { + switch (fmt->exp_max_kind) { + case float_expmax_ieee: + if (likely(frac_eqz(p))) { + p->cls = float_class_inf; + } else { + frac_shl(p, fmt->frac_shift); + p->cls = (parts_is_snan_frac(p->frac_hi, status) + ? float_class_snan : float_class_qnan); + } + return; + case float_expmax_normal: + break; + default: + g_assert_not_reached(); + } + } + + p->cls = float_class_normal; + p->exp -= fmt->exp_bias; + frac_shl(p, fmt->frac_shift); + p->frac_hi |= DECOMPOSED_IMPLICIT_BIT; } /* @@ -314,29 +326,37 @@ static void partsN(uncanon_normal)(FloatPartsN *p, float_status *s, p->frac_lo &= ~round_mask; } - if (fmt->arm_althp) { - /* ARM Alt HP eschews Inf and NaN for a wider exponent. */ - if (unlikely(exp > exp_max)) { - /* Overflow. Return the maximum normal. */ - flags = float_flag_invalid; - exp = exp_max; - frac_allones(p); - p->frac_lo &= ~round_mask; - } - } else if (unlikely(exp >= exp_max)) { - flags |= float_flag_overflow; - if (s->rebias_overflow) { - exp -= fmt->exp_re_bias; - } else if (overflow_norm) { - flags |= float_flag_inexact; - exp = exp_max - 1; - frac_allones(p); - p->frac_lo &= ~round_mask; - } else { - flags |= float_flag_inexact; - p->cls = float_class_inf; - exp = exp_max; - frac_clear(p); + if (unlikely(exp >= exp_max)) { + switch (fmt->exp_max_kind) { + case float_expmax_ieee: + flags |= float_flag_overflow; + if (s->rebias_overflow) { + exp -= fmt->exp_re_bias; + } else if (overflow_norm) { + flags |= float_flag_inexact; + exp = exp_max - 1; + frac_allones(p); + p->frac_lo &= ~round_mask; + } else { + flags |= float_flag_inexact; + p->cls = float_class_inf; + exp = exp_max; + frac_clear(p); + } + break; + + case float_expmax_normal: + if (unlikely(exp > exp_max)) { + /* Overflow. Return the maximum normal. */ + flags = float_flag_invalid; + exp = exp_max; + frac_allones(p); + p->frac_lo &= ~round_mask; + } + break; + + default: + g_assert_not_reached(); } } frac_shr(p, frac_shift); @@ -434,13 +454,13 @@ static void partsN(uncanon)(FloatPartsN *p, float_status *s, frac_clear(p); return; case float_class_inf: - g_assert(!fmt->arm_althp); + assert(fmt->exp_max_kind == float_expmax_ieee); p->exp = fmt->exp_max; frac_clear(p); return; case float_class_qnan: case float_class_snan: - g_assert(!fmt->arm_althp); + assert(fmt->exp_max_kind != float_expmax_normal); p->exp = fmt->exp_max; frac_shr(p, fmt->frac_shift); return; -- 2.43.0
