[perf] vortex 2x as slow with "-vm_size 4M"

_From [derek.br...@gmail.com](https://code.google.com/u/117968039472581148324/) on December 10, 2010 18:06:08_

PR 606113

other benchmarks seem unaffected, but with "-vm_size 4M", vortex takes from
56 mins to 79 mins: with "-vm_size 128M" it takes 37 mins!
(I'm using 4M so I can measure vsz on linux)

I did a debug run at 4M and I see a lot of slowpaths, though I was assuming
this was a DR too-many-resets issue or something
(logs in /work/bugs-drmem/vortex-slow4M/vortex-slow4M.tgz)
addr exceptions: header: 822853032, tls: 0, alloca: 0
Per-opcode slow path executions:
4 add: 1
5 or: 6523
14 cmp: 2
55 mov: 1062
56 mov: 822853115
60 test: 13046
190 cmpxchg: 1
195 movzx: 1
387 movs: 38841
Per-size slow path executions:
1-byte: 822858319
2-byte: 687
4-byte: 53586
8-byte: 0
Other: 0

_Original issue: http://code.google.com/p/drmemory/issues/detail?id=204_