npub1sld6cd53kj8pkz9svnnt54um57nvwrlx9sgya7xhvhl5a5a4f3sq8063kn (npub1sld…63kn) might have something to do with how things pack into op cache lines?
cmp-then-movapd-then-jne is 3 ops
movapd-then-cmp-then-jne can potentially fuse the cmp+jne pair into 1 macro-op, so 2 ops
that cmp is 9 bytes, so pretty big
maybe the extra nop pushes it over some boundary so it can't go into some opcache line and that avoids other hiccups?
Fabian Giesen
npub1sq…rr8se
2023-12-01 21:15:06 UTC
in reply to nevent1q…hy6f
Author Public Key
npub1sqndnjhteg95ss2tk5xdmld540vv8hlhkpa4altk9cagjqrwrvhqurr8sePublished at
2023-12-01 21:15:06 UTCEvent JSON
{
"id": "e7277d830e46089a6631855ca8a55db3f3bd28323f682df36af0e86544a93910",
"pubkey": "8026d9caebca0b48414bb50cddfdb4abd8c3dff7b07b5efd762e3a89006e1b2e",
"created_at": 1701465306,
"kind": 1,
"tags": [
[
"p",
"87dbac3691b48e1b08b064e6ba579ba7a6c70fe62c104ef8d765ff4ed3b54c60",
"wss://relay.mostr.pub"
],
[
"p",
"c1bbeb2e44c2f221c2a3c536a92053ba55dd4a6cad10869d4c79cbfb4db7c59c",
"wss://relay.mostr.pub"
],
[
"e",
"716666f2d444fc1eba7f090b8fcb90ac2644bbffb6e7257f1ede5910b4cd6b32",
"wss://relay.mostr.pub",
"reply"
],
[
"proxy",
"https://mastodon.gamedev.place/users/rygorous/statuses/111507230327509187",
"activitypub"
]
],
"content": "nostr:npub1sld6cd53kj8pkz9svnnt54um57nvwrlx9sgya7xhvhl5a5a4f3sq8063kn might have something to do with how things pack into op cache lines?\n\ncmp-then-movapd-then-jne is 3 ops\nmovapd-then-cmp-then-jne can potentially fuse the cmp+jne pair into 1 macro-op, so 2 ops\n\nthat cmp is 9 bytes, so pretty big\nmaybe the extra nop pushes it over some boundary so it can't go into some opcache line and that avoids other hiccups?",
"sig": "d310f02c32482e7139a5f5ba9a98e8754ad15f6c39b5ec440676102413fceac90ed6672cded3ec101d16ac86332d7206fb28d139b87e077b51b3dfc6f173b640"
}