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From: "Alex Bennée" <alex.bennee@linaro.org>
To: Richard Henderson <richard.henderson@linaro.org>
Cc: qemu-devel@nongnu.org, david@redhat.com
Subject: Re: [PATCH 26/72] softfloat: Convert float128_silence_nan to parts
Date: Thu, 13 May 2021 09:34:27 +0100	[thread overview]
Message-ID: <8735urf2g6.fsf@linaro.org> (raw)
In-Reply-To: <20210508014802.892561-27-richard.henderson@linaro.org>


Richard Henderson <richard.henderson@linaro.org> writes:

> This is the minimal change that also introduces float128_params,
> float128_unpack_raw, and float128_pack_raw without running into
> unused symbol Werrors.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  fpu/softfloat.c                | 96 +++++++++++++++++++++++++++++-----
>  fpu/softfloat-specialize.c.inc | 25 +++------
>  2 files changed, 89 insertions(+), 32 deletions(-)
>
> diff --git a/fpu/softfloat.c b/fpu/softfloat.c
> index 2d6f61ee7a..073b80d502 100644
> --- a/fpu/softfloat.c
> +++ b/fpu/softfloat.c
> @@ -500,14 +500,12 @@ static inline __attribute__((unused)) bool is_qnan(FloatClass c)
>  }
>  
>  /*
> - * Structure holding all of the decomposed parts of a float. The
> - * exponent is unbiased and the fraction is normalized. All
> - * calculations are done with a 64 bit fraction and then rounded as
> - * appropriate for the final format.
> + * Structure holding all of the decomposed parts of a float.
> + * The exponent is unbiased and the fraction is normalized.
>   *
> - * Thanks to the packed FloatClass a decent compiler should be able to
> - * fit the whole structure into registers and avoid using the stack
> - * for parameter passing.
> + * The fraction words are stored in big-endian word ordering,
> + * so that truncation from a larger format to a smaller format
> + * can be done simply by ignoring subsequent elements.
>   */
>  
>  typedef struct {
> @@ -526,6 +524,15 @@ typedef struct {
>      };
>  } FloatParts64;
>  
> +typedef struct {
> +    FloatClass cls;
> +    bool sign;
> +    int32_t exp;
> +    uint64_t frac_hi;
> +    uint64_t frac_lo;
> +} FloatParts128;
> +
> +/* These apply to the most significant word of each FloatPartsN. */
>  #define DECOMPOSED_BINARY_POINT    63
>  #define DECOMPOSED_IMPLICIT_BIT    (1ull << DECOMPOSED_BINARY_POINT)
>  
> @@ -561,11 +568,11 @@ typedef struct {
>      .exp_bias       = ((1 << E) - 1) >> 1,                           \
>      .exp_max        = (1 << E) - 1,                                  \
>      .frac_size      = F,                                             \
> -    .frac_shift     = DECOMPOSED_BINARY_POINT - F,                   \
> -    .frac_lsb       = 1ull << (DECOMPOSED_BINARY_POINT - F),         \
> -    .frac_lsbm1     = 1ull << ((DECOMPOSED_BINARY_POINT - F) - 1),   \
> -    .round_mask     = (1ull << (DECOMPOSED_BINARY_POINT - F)) - 1,   \
> -    .roundeven_mask = (2ull << (DECOMPOSED_BINARY_POINT - F)) - 1
> +    .frac_shift     = (-F - 1) & 63,                                 \
> +    .frac_lsb       = 1ull << ((-F - 1) & 63),                       \
> +    .frac_lsbm1     = 1ull << ((-F - 2) & 63),                       \
> +    .round_mask     = (1ull << ((-F - 1) & 63)) - 1,                 \
> +    .roundeven_mask = (2ull << ((-F - 1) & 63)) - 1
>

I have to admit I find the switch to (-F - 1) & 63 a little black
magical. Isn't the shift always going to end up a factor of the number
of exponent bits we need to move past and the natural size of the
original float?

Anyway my personal brain twisting aside it obviously works and
everything else looks fine so:

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

-- 
Alex Bennée


  reply	other threads:[~2021-05-13  8:51 UTC|newest]

Thread overview: 151+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-08  1:46 [PATCH 00/72] Convert floatx80 and float128 to FloatParts Richard Henderson
2021-05-08  1:46 ` [PATCH 01/72] qemu/host-utils: Use __builtin_bitreverseN Richard Henderson
2021-05-10  9:59   ` Alex Bennée
2021-05-11  9:41   ` David Hildenbrand
2021-05-08  1:46 ` [PATCH 02/72] qemu/host-utils: Add wrappers for overflow builtins Richard Henderson
2021-05-10 10:22   ` Alex Bennée
2021-05-08  1:46 ` [PATCH 03/72] qemu/host-utils: Add wrappers for carry builtins Richard Henderson
2021-05-10 12:57   ` Alex Bennée
2021-05-11 20:10     ` Richard Henderson
2021-05-12 11:17       ` Alex Bennée
2021-05-08  1:46 ` [PATCH 04/72] accel/tcg: Use add/sub overflow routines in tcg-runtime-gvec.c Richard Henderson
2021-05-09  8:43   ` Philippe Mathieu-Daudé
2021-05-10 13:02   ` Alex Bennée
2021-05-11  9:46   ` David Hildenbrand
2021-05-08  1:46 ` [PATCH 05/72] tests/fp: add quad support to the benchmark utility Richard Henderson
2021-05-11 10:01   ` David Hildenbrand
2021-05-08  1:46 ` [PATCH 06/72] softfloat: Move the binary point to the msb Richard Henderson
2021-05-10 13:36   ` Alex Bennée
2021-05-08  1:46 ` [PATCH 07/72] softfloat: Inline float_raise Richard Henderson
2021-05-09  8:32   ` Philippe Mathieu-Daudé
2021-05-11 10:04   ` David Hildenbrand
2021-05-08  1:46 ` [PATCH 08/72] softfloat: Use float_raise in more places Richard Henderson
2021-05-09  8:34   ` Philippe Mathieu-Daudé
2021-05-11 10:06   ` David Hildenbrand
2021-05-08  1:46 ` [PATCH 09/72] softfloat: Tidy a * b + inf return Richard Henderson
2021-05-08  1:47 ` [PATCH 10/72] softfloat: Add float_cmask and constants Richard Henderson
2021-05-08  1:47 ` [PATCH 11/72] softfloat: Use return_nan in float_to_float Richard Henderson
2021-05-10 15:10   ` Alex Bennée
2021-05-11 10:10   ` David Hildenbrand
2021-05-08  1:47 ` [PATCH 12/72] softfloat: fix return_nan vs default_nan_mode Richard Henderson
2021-05-10 15:12   ` Alex Bennée
2021-05-11 10:12   ` David Hildenbrand
2021-05-08  1:47 ` [PATCH 13/72] target/mips: Set set_default_nan_mode with set_snan_bit_is_one Richard Henderson
2021-05-11  9:37   ` Alex Bennée
2021-05-11 10:16   ` David Hildenbrand
2021-05-08  1:47 ` [PATCH 14/72] softfloat: Do not produce a default_nan from parts_silence_nan Richard Henderson
2021-05-11 10:16   ` David Hildenbrand
2021-05-11 10:32   ` Alex Bennée
2021-05-08  1:47 ` [PATCH 15/72] softfloat: Rename FloatParts to FloatParts64 Richard Henderson
2021-05-09  8:45   ` Philippe Mathieu-Daudé
2021-05-11 10:16   ` David Hildenbrand
2021-05-08  1:47 ` [PATCH 16/72] softfloat: Move type-specific pack/unpack routines Richard Henderson
2021-05-09  8:46   ` Philippe Mathieu-Daudé
2021-05-11 10:17   ` David Hildenbrand
2021-05-08  1:47 ` [PATCH 17/72] softfloat: Use pointers with parts_default_nan Richard Henderson
2021-05-11 10:22   ` David Hildenbrand
2021-05-11 20:19     ` Richard Henderson
2021-05-08  1:47 ` [PATCH 18/72] softfloat: Use pointers with unpack_raw Richard Henderson
2021-05-09  8:48   ` Philippe Mathieu-Daudé
2021-05-12 12:58   ` Alex Bennée
2021-05-08  1:47 ` [PATCH 19/72] softfloat: Use pointers with ftype_unpack_raw Richard Henderson
2021-05-11 11:31   ` Alex Bennée
2021-05-08  1:47 ` [PATCH 20/72] softfloat: Use pointers with pack_raw Richard Henderson
2021-05-11 11:32   ` Alex Bennée
2021-05-08  1:47 ` [PATCH 21/72] softfloat: Use pointers with ftype_pack_raw Richard Henderson
2021-05-11 11:32   ` Alex Bennée
2021-05-08  1:47 ` [PATCH 22/72] softfloat: Use pointers with ftype_unpack_canonical Richard Henderson
2021-05-11 13:54   ` Alex Bennée
2021-05-08  1:47 ` [PATCH 23/72] softfloat: Use pointers with ftype_round_pack_canonical Richard Henderson
2021-05-11 13:55   ` Alex Bennée
2021-05-08  1:47 ` [PATCH 24/72] softfloat: Use pointers with parts_silence_nan Richard Henderson
2021-05-11 13:56   ` Alex Bennée
2021-05-08  1:47 ` [PATCH 25/72] softfloat: Rearrange FloatParts64 Richard Henderson
2021-05-11 13:57   ` Alex Bennée
2021-05-11 15:04     ` Richard Henderson
2021-05-12 11:08       ` Alex Bennée
2021-05-08  1:47 ` [PATCH 26/72] softfloat: Convert float128_silence_nan to parts Richard Henderson
2021-05-13  8:34   ` Alex Bennée [this message]
2021-05-13 12:25     ` Richard Henderson
2021-05-08  1:47 ` [PATCH 27/72] softfloat: Convert float128_default_nan " Richard Henderson
2021-05-13  8:56   ` Alex Bennée
2021-05-08  1:47 ` [PATCH 28/72] softfloat: Move return_nan to softfloat-parts.c.inc Richard Henderson
2021-05-12 18:10   ` David Hildenbrand
2021-05-08  1:47 ` [PATCH 29/72] softfloat: Move pick_nan " Richard Henderson
2021-05-12 18:16   ` David Hildenbrand
2021-05-13 12:28     ` Richard Henderson
2021-05-08  1:47 ` [PATCH 30/72] softfloat: Move pick_nan_muladd " Richard Henderson
2021-05-12 18:18   ` David Hildenbrand
2021-05-08  1:47 ` [PATCH 31/72] softfloat: Move sf_canonicalize " Richard Henderson
2021-05-13  9:45   ` Alex Bennée
2021-05-08  1:47 ` [PATCH 32/72] softfloat: Move round_canonical " Richard Henderson
2021-05-13  9:53   ` Alex Bennée
2021-05-08  1:47 ` [PATCH 33/72] softfloat: Use uadd64_carry, usub64_borrow in softfloat-macros.h Richard Henderson
2021-05-13 10:00   ` Alex Bennée
2021-05-13 12:38     ` Richard Henderson
2021-05-08  1:47 ` [PATCH 34/72] softfloat: Move addsub_floats to softfloat-parts.c.inc Richard Henderson
2021-05-13 10:03   ` Alex Bennée
2021-05-13 10:05   ` Alex Bennée
2021-05-08  1:47 ` [PATCH 35/72] softfloat: Implement float128_add/sub via parts Richard Henderson
2021-05-13 10:06   ` Alex Bennée
2021-05-08  1:47 ` [PATCH 36/72] softfloat: Move mul_floats to softfloat-parts.c.inc Richard Henderson
2021-05-13 10:08   ` Alex Bennée
2021-05-08  1:47 ` [PATCH 37/72] softfloat: Move muladd_floats " Richard Henderson
2021-05-13 10:43   ` Alex Bennée
2021-05-08  1:47 ` [PATCH 38/72] softfloat: Use mulu64 for mul64To128 Richard Henderson
2021-05-08  1:47 ` [PATCH 39/72] softfloat: Use add192 in mul128To256 Richard Henderson
2021-05-13 10:49   ` Alex Bennée
2021-05-08  1:47 ` [PATCH 40/72] softfloat: Tidy mul128By64To192 Richard Henderson
2021-05-13 10:50   ` Alex Bennée
2021-05-08  1:47 ` [PATCH 41/72] softfloat: Introduce sh[lr]_double primitives Richard Henderson
2021-05-13 10:59   ` Alex Bennée
2021-05-08  1:47 ` [PATCH 42/72] softfloat: Move div_floats to softfloat-parts.c.inc Richard Henderson
2021-05-13 11:02   ` Alex Bennée
2021-05-08  1:47 ` [PATCH 43/72] softfloat: Split float_to_float Richard Henderson
2021-05-13 11:04   ` Alex Bennée
2021-05-08  1:47 ` [PATCH 44/72] softfloat: Convert float-to-float conversions with float128 Richard Henderson
2021-05-13 11:17   ` Alex Bennée
2021-05-08  1:47 ` [PATCH 45/72] softfloat: Move round_to_int to softfloat-parts.c.inc Richard Henderson
2021-05-13 14:10   ` Alex Bennée
2021-05-08  1:47 ` [PATCH 46/72] softfloat: Move rount_to_int_and_pack " Richard Henderson
2021-05-13 14:11   ` Alex Bennée
2021-05-08  1:47 ` [PATCH 47/72] softfloat: Move rount_to_uint_and_pack " Richard Henderson
2021-05-08  1:47 ` [PATCH 48/72] softfloat: Move int_to_float " Richard Henderson
2021-05-08  1:47 ` [PATCH 49/72] softfloat: Move uint_to_float " Richard Henderson
2021-05-08  1:47 ` [PATCH 50/72] softfloat: Move minmax_flags " Richard Henderson
2021-05-17 13:14   ` David Hildenbrand
2021-05-17 15:57     ` Richard Henderson
2021-05-08  1:47 ` [PATCH 51/72] softfloat: Move compare_floats " Richard Henderson
2021-05-08  1:47 ` [PATCH 52/72] softfloat: Move scalbn_decomposed " Richard Henderson
2021-05-08  1:47 ` [PATCH 53/72] softfloat: Move sqrt_float " Richard Henderson
2021-05-08  1:47 ` [PATCH 54/72] softfloat: Split out parts_uncanon_normal Richard Henderson
2021-05-08  1:47 ` [PATCH 55/72] softfloat: Reduce FloatFmt Richard Henderson
2021-05-08  1:47 ` [PATCH 56/72] softfloat: Introduce Floatx80RoundPrec Richard Henderson
2021-05-08  1:47 ` [PATCH 57/72] softfloat: Adjust parts_uncanon_normal for floatx80 Richard Henderson
2021-05-08  1:47 ` [PATCH 58/72] tests/fp/fp-test: Reverse order of floatx80 precision tests Richard Henderson
2021-05-13 14:12   ` Alex Bennée
2021-05-08  1:47 ` [PATCH 59/72] softfloat: Convert floatx80_add/sub to FloatParts Richard Henderson
2021-05-08  1:47 ` [PATCH 60/72] softfloat: Convert floatx80_mul " Richard Henderson
2021-05-08  1:47 ` [PATCH 61/72] softfloat: Convert floatx80_div " Richard Henderson
2021-05-08  1:47 ` [PATCH 62/72] softfloat: Convert floatx80_sqrt " Richard Henderson
2021-05-08  1:47 ` [PATCH 63/72] softfloat: Convert floatx80_round " Richard Henderson
2021-05-08  1:47 ` [PATCH 64/72] softfloat: Convert floatx80_round_to_int " Richard Henderson
2021-05-08  1:47 ` [PATCH 65/72] softfloat: Convert integer to floatx80 " Richard Henderson
2021-05-08  1:47 ` [PATCH 66/72] softfloat: Convert floatx80 float conversions " Richard Henderson
2021-05-08  1:47 ` [PATCH 67/72] softfloat: Convert floatx80 to integer " Richard Henderson
2021-05-08  1:47 ` [PATCH 68/72] softfloat: Convert floatx80_scalbn " Richard Henderson
2021-05-08  1:47 ` [PATCH 69/72] softfloat: Convert floatx80 compare " Richard Henderson
2021-05-08  1:48 ` [PATCH 70/72] softfloat: Convert float32_exp2 " Richard Henderson
2021-05-08  1:48 ` [PATCH 71/72] softfloat: Move floatN_log2 to softfloat-parts.c.inc Richard Henderson
2021-05-08  1:48 ` [PATCH 72/72] softfloat: Convert modrem operations to FloatParts Richard Henderson
2021-05-08  2:52 ` [PATCH 00/72] Convert floatx80 and float128 " no-reply
2021-05-10 13:36 ` Alex Bennée
2021-05-12  1:52   ` Richard Henderson
2021-05-12 11:22     ` Alex Bennée
2021-05-12 15:28       ` Richard Henderson
2021-05-12 16:47 ` Alex Bennée
2021-05-12 19:23 ` Alex Bennée
2021-05-13 11:49   ` Richard Henderson
2021-05-13 13:33     ` Alex Bennée
2021-05-13 23:54       ` Richard Henderson
2021-05-13 14:13 ` Alex Bennée

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