perf: vtune results: jecxz is bad: experiment w/ jecxz-less ibl

_From [derek.br...@gmail.com](https://code.google.com/u/117968039472581148324/) on February 21, 2009 11:00:26_

this was PR 212436

latest renewal of vtune analysis perfctr evidence points at jecxz causing
problems
though in branch misprediction, surprisingly
we have a list of cases to file from our last analysis
following up on only one of them here:
two efficient ways to eliminate jecxz:
- PR 208795/PR 212049: spill eax,flags and use cmp,jne, w/ ecx spill off
hit path to offset eax/flags preservation
- PR 211955: recreate eflags on miss before go to ibl or on hit if live
post-cmp

_Original issue: http://code.google.com/p/dynamorio/issues/detail?id=33_