From: David Hildenbrand <david@redhat.com>
To: Richard Henderson <richard.henderson@linaro.org>, qemu-devel@nongnu.org
Cc: alex.bennee@linaro.org, bharata@linux.ibm.com
Subject: Re: [PATCH 4/8] softfloat: Add float_cmask and constants
Date: Thu, 24 Sep 2020 09:40:40 +0200 [thread overview]
Message-ID: <bee4024b-84c3-ec01-d49c-4d40064a13ca@redhat.com> (raw)
In-Reply-To: <20200924012453.659757-5-richard.henderson@linaro.org>
On 24.09.20 03:24, Richard Henderson wrote:
> Testing more than one class at a time is better done with masks.
> This reduces the static branch count.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> fpu/softfloat.c | 31 ++++++++++++++++++++++++-------
> 1 file changed, 24 insertions(+), 7 deletions(-)
>
> diff --git a/fpu/softfloat.c b/fpu/softfloat.c
> index 9db55d2b11..3e625c47cd 100644
> --- a/fpu/softfloat.c
> +++ b/fpu/softfloat.c
> @@ -469,6 +469,20 @@ typedef enum __attribute__ ((__packed__)) {
> float_class_snan,
> } FloatClass;
>
> +#define float_cmask(bit) (1u << (bit))
> +
> +enum {
> + float_cmask_zero = float_cmask(float_class_zero),
> + float_cmask_normal = float_cmask(float_class_normal),
> + float_cmask_inf = float_cmask(float_class_inf),
> + float_cmask_qnan = float_cmask(float_class_qnan),
> + float_cmask_snan = float_cmask(float_class_snan),
> +
> + float_cmask_infzero = float_cmask_zero | float_cmask_inf,
> + float_cmask_anynan = float_cmask_qnan | float_cmask_snan,
> +};
> +
> +
> /* Simple helpers for checking if, or what kind of, NaN we have */
> static inline __attribute__((unused)) bool is_nan(FloatClass c)
> {
> @@ -1335,24 +1349,27 @@ bfloat16 QEMU_FLATTEN bfloat16_mul(bfloat16 a, bfloat16 b, float_status *status)
> static FloatParts muladd_floats(FloatParts a, FloatParts b, FloatParts c,
> int flags, float_status *s)
> {
> - bool inf_zero = ((1 << a.cls) | (1 << b.cls)) ==
> - ((1 << float_class_inf) | (1 << float_class_zero));
> - bool p_sign;
> + bool inf_zero, p_sign;
> bool sign_flip = flags & float_muladd_negate_result;
> FloatClass p_class;
> uint64_t hi, lo;
> int p_exp;
> + int ab_mask, abc_mask;
> +
> + ab_mask = float_cmask(a.cls) | float_cmask(b.cls);
> + abc_mask = float_cmask(c.cls) | ab_mask;
> + inf_zero = ab_mask == float_cmask_infzero;
>
> /* It is implementation-defined whether the cases of (0,inf,qnan)
> * and (inf,0,qnan) raise InvalidOperation or not (and what QNaN
> * they return if they do), so we have to hand this information
> * off to the target-specific pick-a-NaN routine.
> */
> - if (is_nan(a.cls) || is_nan(b.cls) || is_nan(c.cls)) {
> + if (unlikely(abc_mask & float_cmask_anynan)) {
> return pick_nan_muladd(a, b, c, inf_zero, s);
> }
>
> - if (inf_zero) {
> + if (unlikely(inf_zero)) {
> s->float_exception_flags |= float_flag_invalid;
> return parts_default_nan(s);
> }
> @@ -1367,9 +1384,9 @@ static FloatParts muladd_floats(FloatParts a, FloatParts b, FloatParts c,
> p_sign ^= 1;
> }
>
> - if (a.cls == float_class_inf || b.cls == float_class_inf) {
> + if (ab_mask & float_cmask_inf) {
> p_class = float_class_inf;
> - } else if (a.cls == float_class_zero || b.cls == float_class_zero) {
> + } else if (ab_mask & float_cmask_zero) {
> p_class = float_class_zero;
> } else {
> p_class = float_class_normal;
>
Reviewed-by: David Hildenbrand <david@redhat.com>
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2020-09-24 7:44 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-24 1:24 [PATCH 0/8] softfloat: Implement float128_muladd Richard Henderson
2020-09-24 1:24 ` [PATCH 1/8] softfloat: Use mulu64 for mul64To128 Richard Henderson
2020-09-24 7:32 ` David Hildenbrand
2020-09-24 1:24 ` [PATCH 2/8] softfloat: Use int128.h for some operations Richard Henderson
2020-09-24 7:35 ` David Hildenbrand
2020-09-24 1:24 ` [PATCH 3/8] softfloat: Tidy a * b + inf return Richard Henderson
2020-09-24 7:37 ` David Hildenbrand
2020-09-24 1:24 ` [PATCH 4/8] softfloat: Add float_cmask and constants Richard Henderson
2020-09-24 7:40 ` David Hildenbrand [this message]
2020-09-24 1:24 ` [PATCH 5/8] softfloat: Inline pick_nan_muladd into its caller Richard Henderson
2020-09-24 7:42 ` David Hildenbrand
2020-09-24 1:24 ` [PATCH 6/8] softfloat: Implement float128_muladd Richard Henderson
2020-09-24 7:56 ` David Hildenbrand
2020-09-24 13:30 ` Richard Henderson
2020-09-25 9:17 ` David Hildenbrand
2020-09-24 1:24 ` [PATCH 7/8] softfloat: Use x86_64 assembly for {add,sub}{192,256} Richard Henderson
2020-09-24 1:24 ` [PATCH 8/8] softfloat: Use aarch64 " Richard Henderson
2020-09-24 8:00 ` [PATCH 0/8] softfloat: Implement float128_muladd David Hildenbrand
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