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(parent: f65557e) | patch
Provide workaround for a performance issue with the popcnt instruction
authorKonstantin Belousov <kib@FreeBSD.org>
Tue, 31 Mar 2015 01:44:07 +0000 (01:44 +0000)
committerKonstantin Belousov <kib@FreeBSD.org>
Tue, 31 Mar 2015 01:44:07 +0000 (01:44 +0000)
commit333d2959464375d2677cd834fb597acc84305649
tree4bb6bdc20e9e9af4ec3c874aada0faef61adaac2tree | snapshot
parentf65557efc4982615f269892107e1ba1ed5a89caacommit | diff
Provide workaround for a performance issue with the popcnt instruction
on Intel processors.  Clear spurious dependency by explicitely xoring
the destination register of popcnt.

Use bitcount64() instead of re-implementing SWAR locally, for
processors without popcnt instruction.

Reviewed by: jhb
Discussed with: jilles (previous version)
Sponsored by: The FreeBSD Foundation
sys/amd64/amd64/pmap.c diff | blob | history
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