Re: [PATCH 14/12] libgcc _BitInt helper documentation [PR102989]

[Joseph Myers <joseph@codesourcery.com>]

On Tue, 22 Aug 2023, Jakub Jelinek via Gcc-patches wrote:

> +significant limb if @var{N} is not divisible by

@var{N} should be @var{n}, throughout.

> +@deftypefn {Runtime Function} void __bid_fixsdbitint (@code{UBILtype} *@var{r}, int32_t @var{rprec}, _Decimal32 @var{a})
> +@deftypefnx {Runtime Function} void __bid_fixddbitint (@code{UBILtype} *@var{r}, int32_t @var{rprec}, _Decimal64 @var{a})
> +@deftypefnx {Runtime Function} void __bid_fixtdbitint (@code{UBILtype} *@var{r}, int32_t @var{rprec}, _Decimal128 @var{a})
> +These functions convert @var{a} to bit-precise integer @var{r}, rounding toward zero.
> +If @var{rprec} is positive, it converts to unsigned bit-precise integer and
> +negative values all become zero, if @var{rprec} is negative, it converts
> +to signed bit-precise integer.
> +@end deftypefn
> +
> +@deftypefn {Runtime Function} _Decimal32 __bid_floatbitintsd (@code{UBILtype} *@var{i}, int32_t @var{iprec})
> +@deftypefnx {Runtime Function} _Decimal64 __bid_floatbitintdd (@code{UBILtype} *@var{i}, int32_t @var{iprec})
> +@deftypefnx {Runtime Function} _Decimal128 __bid_floatbitinttd (@code{UBILtype} *@var{i}, int32_t @var{iprec})
> +These functions convert bit-precise integer @var{i} to decimal floating point.  If
> +@var{iprec} is positive, it is conversion from unsigned bit-precise integer,
> +otherwise from signed bit-precise integer.
> +@end deftypefn

The documentation for __bid_* should say explicitly that these functions 
are for BID format (assuming it's intended that functions for DPD format 
should use __dpd_* when support is added for an architecture using DPD).

> +/* Common final part of __fix?fbitint conversion functions.
> +   The A floating point value should have been converted using
> +   soft-fp macros into RV, U##DI##type DI##_BITS precise normal
> +   integral type and SHIFT, how many bits should that value be
> +   shifted to the left.  R is pointer to limbs array passed to the
> +   function, RN number of limbs in it, ARPREC absolute value of
> +   RPREC argument passed to it, RSIZE number of significant bits in RV.
> +   RSIGNED is non-zero if the result is signed bit-precise integer,
> +   otherwise zero.  If OVF is true, instead of storing RV shifted left
> +   by SHIFT bits and zero or sign extended store minimum or maximum
> +   of the signed or unsigned bit-precise integer type depending on if
> +   RV contains the minimum or maximum signed or unsigned value.  */

As I understand it, OVF is also for the case of a zero result from input 
close to zero, for signed types (when that's not the maximum or minimum) 
in addition to unsigned types.

> +/* Common initial part of __floatbitint?f conversion functions.
> +   I and IPREC are arguments passed to those functions, convert that
> +   into a pair of DI##type IV integer and SHIFT, such that converting
> +   IV to floating point and multiplicating that by pow (2, SHIFT)
> +   gives the expected result.  IV size needs to be chosen such that
> +   it is large than number of bits in floating-point mantissa and

"large than" -> "larger than".

This patch is OK with those fixes.

-- 
Joseph S. Myers
joseph@codesourcery.com