Hi liguang, On Tue, Apr 09, 2013 at 04:21:10PM +0800, li guang wrote: > 在 2013-04-09二的 10:11 +0200,Paolo Bonzini写道: > > Il 09/04/2013 10:05, 陳韋任 (Wei-Ren Chen) ha scritto: > > > Hi liguang, > > > > > > Just to be curious, how much performance improvement this patch can get? > > > > I think zero. It is indeed making the code a tiny bit more readable in > > the 2nd/3rd/5th/6th hunks. > > I think maybe a little greater than 0, > for it optimizes a variable 'lj' increment.
As Peter said, only profiling can show if there is a performance improvement. > > But the 1st and 4th hunks, which do > > > > - num_insns = 0; > > > > are wrong. I'm surprised the compiler doesn't report usage of an > > uninitialized variable. liguang, how did you test them? > > I do normal compile and run guest OS for TCG, > I think 'max_insns = tb->cflags & CF_COUNT_MASK;' is enough > to feed compiler. num_insns and max_insns are two different variables, right? So this assignment does not do anything with num_insns. Regards, chenwj -- Wei-Ren Chen (陳韋任) Computer Systems Lab, Institute of Information Science, Academia Sinica, Taiwan (R.O.C.) Tel:886-2-2788-3799 #1667 Homepage: http://people.cs.nctu.edu.tw/~chenwj