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* [Bug target/114835] New: AVR popcountqi2 is not fast&small as can be @ 2024-04-24 15:20 WolfgaNg.Hospital at arcor dot de 2024-05-07 14:32 ` [Bug target/114835] " cvs-commit at gcc dot gnu.org ` (2 more replies) 0 siblings, 3 replies; 4+ messages in thread From: WolfgaNg.Hospital at arcor dot de @ 2024-04-24 15:20 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114835 Bug ID: 114835 Summary: AVR popcountqi2 is not fast&small as can be Product: gcc Version: 13.2.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: target Assignee: unassigned at gcc dot gnu.org Reporter: WolfgaNg.Hospital at arcor dot de Target Milestone: --- Created attachment 58025 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=58025&action=edit AVR assembly code for __popcountqi2 For 8-bit AVRs, the current 16-instruction __popcountqi2 uses 6 ADC instructions to establish the number of bits set in a byte. In "Bit Twiddling Hacks", Sean E. Anderson presents several approaches to this; "parallel/sideways addition" can be coded with one instruction&cycle less. When establishing the "popcount" of an uint8_t, I've seen GCC to widen the value to "half int" and use __popcountqi2 twice. ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/114835] AVR popcountqi2 is not fast&small as can be 2024-04-24 15:20 [Bug target/114835] New: AVR popcountqi2 is not fast&small as can be WolfgaNg.Hospital at arcor dot de @ 2024-05-07 14:32 ` cvs-commit at gcc dot gnu.org 2024-05-07 15:12 ` gjl at gcc dot gnu.org 2024-05-07 15:14 ` gjl at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: cvs-commit at gcc dot gnu.org @ 2024-05-07 14:32 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114835 --- Comment #1 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Georg-Johann Lay <gjl@gcc.gnu.org>: https://gcc.gnu.org/g:8d2c93fcfe1afc5291bbbe162c3b7ad5764f6d8d commit r15-286-g8d2c93fcfe1afc5291bbbe162c3b7ad5764f6d8d Author: Wolfgang Hospital <Wolfgang.Hospital@arcor.de> Date: Tue May 7 16:24:39 2024 +0200 AVR: target/114835 - Tweak popcountqi2 libgcc/ PR target/114835 * config/avr/lib1funcs.S (__popcountqi2): Use code that is one instruction shorter / faster. ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/114835] AVR popcountqi2 is not fast&small as can be 2024-04-24 15:20 [Bug target/114835] New: AVR popcountqi2 is not fast&small as can be WolfgaNg.Hospital at arcor dot de 2024-05-07 14:32 ` [Bug target/114835] " cvs-commit at gcc dot gnu.org @ 2024-05-07 15:12 ` gjl at gcc dot gnu.org 2024-05-07 15:14 ` gjl at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: gjl at gcc dot gnu.org @ 2024-05-07 15:12 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114835 Georg-Johann Lay <gjl at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED Resolution|--- |FIXED --- Comment #2 from Georg-Johann Lay <gjl at gcc dot gnu.org> --- Fixed in v15. ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/114835] AVR popcountqi2 is not fast&small as can be 2024-04-24 15:20 [Bug target/114835] New: AVR popcountqi2 is not fast&small as can be WolfgaNg.Hospital at arcor dot de 2024-05-07 14:32 ` [Bug target/114835] " cvs-commit at gcc dot gnu.org 2024-05-07 15:12 ` gjl at gcc dot gnu.org @ 2024-05-07 15:14 ` gjl at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: gjl at gcc dot gnu.org @ 2024-05-07 15:14 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114835 --- Comment #3 from Georg-Johann Lay <gjl at gcc dot gnu.org> --- (In reply to Wolfgang Hospital from comment #0) > When establishing the "popcount" of an uint8_t, I've seen GCC to widen the > value to "half int" and use __popcountqi2 twice. This is a different issue, please f'up PR114975. ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2024-05-07 15:14 UTC | newest] Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2024-04-24 15:20 [Bug target/114835] New: AVR popcountqi2 is not fast&small as can be WolfgaNg.Hospital at arcor dot de 2024-05-07 14:32 ` [Bug target/114835] " cvs-commit at gcc dot gnu.org 2024-05-07 15:12 ` gjl at gcc dot gnu.org 2024-05-07 15:14 ` gjl at gcc dot gnu.org
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