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* [Bug other/55899] New: GCC should provide built-ins in <stdint.h> data types flavor/version/variation
@ 2013-01-07 15:15 yann at droneaud dot fr
2013-01-10 17:30 ` [Bug other/55899] " hp at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: yann at droneaud dot fr @ 2013-01-07 15:15 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55899
Bug #: 55899
Summary: GCC should provide built-ins in <stdint.h> data types
flavor/version/variation
Classification: Unclassified
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: other
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: yann@droneaud.fr
Built-in functions such as
__builtin_clz(unsigned int x)
__builtin_ctz(unsigned int x)
__builtin_ffs(unsigned int x)
etc.
are lacking variant based on C99 <stdint.h> data type.
Currently there's
__builtin_clzl(unsigned long x)
__builtin_clzll(unsigned long long x)
I'd like to have:
__builtin_clz32(uint32_t x)
__builtin_clz64(uint64_t x)
This would help to hard code the number of bits when using such construct to
know the number of bit needed to hold a value:
(8 * sizeof(unsigned int)) - __builtin_clz(value)
when value is of type uint32_t:
32 - __builtin_clz32(value)
Note: there's already __builtin_bswap32(int32_t x) and
__builtin_bswap64(int64_t x)
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug other/55899] GCC should provide built-ins in <stdint.h> data types flavor/version/variation
2013-01-07 15:15 [Bug other/55899] New: GCC should provide built-ins in <stdint.h> data types flavor/version/variation yann at droneaud dot fr
@ 2013-01-10 17:30 ` hp at gcc dot gnu.org
2022-11-29 11:45 ` yann at droneaud dot fr
2022-11-29 18:59 ` joseph at codesourcery dot com
2 siblings, 0 replies; 4+ messages in thread
From: hp at gcc dot gnu.org @ 2013-01-10 17:30 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55899
Hans-Peter Nilsson <hp at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2013-01-10
CC| |hp at gcc dot gnu.org
Ever Confirmed|0 |1
--- Comment #1 from Hans-Peter Nilsson <hp at gcc dot gnu.org> 2013-01-10 17:29:48 UTC ---
Sounds fair. Note the inconsistency between clz/ctz builtins and bswap
builtins.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug other/55899] GCC should provide built-ins in <stdint.h> data types flavor/version/variation
2013-01-07 15:15 [Bug other/55899] New: GCC should provide built-ins in <stdint.h> data types flavor/version/variation yann at droneaud dot fr
2013-01-10 17:30 ` [Bug other/55899] " hp at gcc dot gnu.org
@ 2022-11-29 11:45 ` yann at droneaud dot fr
2022-11-29 18:59 ` joseph at codesourcery dot com
2 siblings, 0 replies; 4+ messages in thread
From: yann at droneaud dot fr @ 2022-11-29 11:45 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55899
Yann Droneaud <yann at droneaud dot fr> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |yann at droneaud dot fr
--- Comment #2 from Yann Droneaud <yann at droneaud dot fr> ---
I stumbled upon this issue again when dealing with uint64_t as sometimes it's
defined as unsigned long, sometimes it's defined as unsigned long long
depending on the ABI. Having __builtin_ffs64(), __builtin_clz64(),
__builtin_ctz64(), etc. would ease me making my code portable to unpleasant ABI
such as Microsoft Windows ones without having to use GCC's
__builtin_types_compatible_p() (which is not supported when compiling C++), or
C11 _Generic() ...
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug other/55899] GCC should provide built-ins in <stdint.h> data types flavor/version/variation
2013-01-07 15:15 [Bug other/55899] New: GCC should provide built-ins in <stdint.h> data types flavor/version/variation yann at droneaud dot fr
2013-01-10 17:30 ` [Bug other/55899] " hp at gcc dot gnu.org
2022-11-29 11:45 ` yann at droneaud dot fr
@ 2022-11-29 18:59 ` joseph at codesourcery dot com
2 siblings, 0 replies; 4+ messages in thread
From: joseph at codesourcery dot com @ 2022-11-29 18:59 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55899
--- Comment #3 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
C2x <stdbit.h> provides type-generic versions of various such operations,
in addition to type-specific versions (but the type-specific versions are
for unsigned char through unsigned long long, so don't themselves address
the issue from this PR, and my view is that type-generic functions are
error-prone in cases, such as clz, where the result depends on the type
and not just the integer value of the argument).
Since <stdbit.h> is a library facility (with functions thus expected to be
available with external linkage to link against whether or not the header
is included) I expect to implement it in due course in glibc, not GCC,
though as usual built-in functions with the standard names would be
appropriate in GCC.
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2022-11-29 18:59 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2013-01-07 15:15 [Bug other/55899] New: GCC should provide built-ins in <stdint.h> data types flavor/version/variation yann at droneaud dot fr
2013-01-10 17:30 ` [Bug other/55899] " hp at gcc dot gnu.org
2022-11-29 11:45 ` yann at droneaud dot fr
2022-11-29 18:59 ` joseph at codesourcery dot com
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