On Thu, Jan 05, 2023 at 08:09:19AM +0100, Morten Brørup wrote: > > From: Tyler Retzlaff [mailto:roret...@linux.microsoft.com] > > Sent: Thursday, 24 November 2022 00.43 > > > > Provide an abstraction for leading and trailing zero bit counting > > functions to hide compiler specific intrinsics and builtins. > > > > Signed-off-by: Tyler Retzlaff <roret...@linux.microsoft.com> > > --- > > lib/eal/include/meson.build | 1 + > > lib/eal/include/rte_bitcount.h | 265 > > +++++++++++++++++++++++++++++++++++++++++ > > 2 files changed, 266 insertions(+) > > create mode 100644 lib/eal/include/rte_bitcount.h > > > > diff --git a/lib/eal/include/meson.build b/lib/eal/include/meson.build > > index cfcd40a..8ff1d65 100644 > > --- a/lib/eal/include/meson.build > > +++ b/lib/eal/include/meson.build > > @@ -5,6 +5,7 @@ includes += include_directories('.') > > > > headers += files( > > 'rte_alarm.h', > > + 'rte_bitcount.h', > > 'rte_bitmap.h', > > 'rte_bitops.h', > > 'rte_branch_prediction.h', > > diff --git a/lib/eal/include/rte_bitcount.h > > b/lib/eal/include/rte_bitcount.h > > new file mode 100644 > > index 0000000..587de52 > > --- /dev/null > > +++ b/lib/eal/include/rte_bitcount.h > > @@ -0,0 +1,265 @@ > > +/* SPDX-License-Identifier: BSD-3-Clause > > + * Copyright (C) 2022 Microsoft Corporation > > + */ > > + > > +#ifndef _RTE_BITCOUNT_H_ > > +#define _RTE_BITCOUNT_H_ > > + > > +#include <rte_compat.h> > > + > > +#ifdef __cplusplus > > +extern "C" { > > +#endif > > + > > +#ifdef RTE_TOOLCHAIN_MSVC > > + > > +/** > > + * @warning > > + * @b EXPERIMENTAL: this API may change, or be removed, without prior > > notice > > + * > > + * Get the count of leading 0-bits in v. > > + * > > + * @param v > > + * The value. > > + * @return > > + * The count of leading zero bits. > > + */ > > +__rte_experimental > > +static inline unsigned int > > +rte_clz(unsigned int v) > > +{ > > + unsigned long rv; > > + > > + (void)_BitScanReverse(&rv, v); > > + > > + return (unsigned int)rv; > > +} > > + > > +/** > > + * @warning > > + * @b EXPERIMENTAL: this API may change, or be removed, without prior > > notice > > + * > > + * Get the count of leading 0-bits in v. > > + * > > + * @param v > > + * The value. > > + * @return > > + * The count of leading zero bits. > > + */ > > +__rte_experimental > > +static inline unsigned int > > +rte_clzl(unsigned long v) > > Don't use l (long) and ll (long long) for names (and types), use explicit bit > lengths, 32 and 64. > > E.g.: rte_clz32(uint32_t v)
so i just noticed this, but sometimes these functions receive size_t so naming them specifically 32/64 bit becomes problematic because are going to end up with promotion on sizeof(size_t) == sizeof(long) == 4 platforms. i.e. size_t s = ...; x = rte_clz64(s); // assume 64-bit today this code is now broken because on 32-bit platform s will get promoted and the extra 32 zero-bits will be returned in the result breaking calculations. any thoughts? should we go back to l, ll? ty
