Opened 12 years ago

Closed 11 years ago

#5175 closed defect (fixed)

Fast CMOV test in configure is broken

Reported by: Dagmar d'Surreal Owned by: Janne Grunau
Priority: trivial Milestone: 0.22
Component: mythtv Version: 0.21-fixes
Severity: low Keywords:
Cc: Ticket locked: no

Description

Currently the logic for selecting for fast CMOV or slower CMOV (Netburst-based CPUs) is broken and appears to be assuming a slower CMOV and only enables fast_cmov when a CPU detection override is called for.

This could result in AVC CABAC decoding going slower than it should (from what I gather by reading piles of discussions from the ffmpeg mailing list).

Note this has nothing to do with those cheapie CPUs (*kof*C3*kof*) that don't support CMOV at all--that is being checked for elsewhere and looks correct enough.

Attachments (1)

mythtv-0.21f-fast_cmov_fix.diff (748 bytes) - added by Dagmar d'Surreal 12 years ago.
Fixes selection of cmov/fast_cmov

Download all attachments as: .zip

Change History (6)

Changed 12 years ago by Dagmar d'Surreal

Fixes selection of cmov/fast_cmov

comment:1 Changed 12 years ago by Dagmar d'Surreal

See also http://article.gmane.org/gmane.comp.video.mplayer.devel/40328 for the same issue for a different project (MPlayer) and a _very_ simple explanation.

comment:2 Changed 11 years ago by stuartm

Owner: changed from Isaac Richards to stuartm
Status: newaccepted

comment:3 Changed 11 years ago by Janne Grunau

Milestone: 0.21.10.22
Owner: changed from stuartm to Janne Grunau

the patch is wrong. $cpu is "generic" if it wasn't overriden.

I'll commit a proper fix soon.

comment:4 Changed 11 years ago by Janne Grunau

(In [18564]) move --enable-proc-opt cpu detection in configure

set cpu instead of ARCHFLAGS directly. this fixes cmov detection for --enable-proc-opt and removes some differences to ffmpeg's configure. Various configure cleanups Refs #5175

comment:5 Changed 11 years ago by Janne Grunau

Resolution: fixed
Status: acceptedclosed
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