improve callstack walk perf further

_From [bruen...@google.com](https://code.google.com/u/109494838902877177630/) on December 07, 2011 22:14:44_

this issue extends issue #460 but for malloc interception for leak detection where callstacks are gathered on every malloc, though there are far fewer low-hanging fruits here b/c this has been profiled and optimized in the past.

I did a bunch of performance improvements on callstack walking for
Dr. Heapstat (xref PR 473640), resulting in today's optimized in-module
checks, lowest-frame checks, DRi#228, DRi#226, and packed_callstack_hash().

*\* TODO cfrac on Windows built /Ox /Oy-

now we avoid fp scans (xref issue #460 #s):

app mallocs: 10890330, frees: 10890127, large mallocs: 0
unique malloc stacks: 7050289
callstack fp scans: 0
callstack is_retaddr: 10890130, backdecode: 10890130, unreadable: 0

**\* INFO times for different modes

this is after issue #460 A through L

script:
echo native
for ((i=0; i<3; i++)); do
/usr/bin/time ./cfrac.exe 41757646344123832613190542166099121 2>&1 | grep system
done
echo DR
for ((i=0; i<3; i++)); do
/usr/bin/time ~/dr/git/exports/bin32/drrun.exe -quiet ./cfrac.exe 41757646344123832613190542166099121 2>&1 | grep system
done
for j in "" "-no_count_leaks" "-no_check_uninitialized" "-no_check_uninitialized -no_count_leaks" "-leaks_only" "-leaks_only -no_zero_stack" "-leaks_only -no_count_leaks" "-leaks_only -no_count_leaks -no_track_allocs"; do
echo $j
for ((i=0; i<3; i++)); do
/usr/bin/time ~/drmemory/git/build_drmem_rel/bin/drmemory.exe $j -quiet -dr c:/src/dr/git/exports -batch -- ./cfrac.exe 41757646344123832613190542166099121 2>&1 | grep system
done
done

native
0.00user 0.01system 0:01.74elapsed 0%CPU (0avgtext+0avgdata 234752maxresident)k
0.00user 0.01system 0:01.69elapsed 0%CPU (0avgtext+0avgdata 234240maxresident)k
0.00user 0.01system 0:01.72elapsed 0%CPU (0avgtext+0avgdata 234240maxresident)k
DR
0.01user 0.00system 0:02.40elapsed 0%CPU (0avgtext+0avgdata 234240maxresident)k
0.00user 0.01system 0:02.39elapsed 0%CPU (0avgtext+0avgdata 234496maxresident)k
0.01user 0.00system 0:02.40elapsed 0%CPU (0avgtext+0avgdata 234240maxresident)k
(drmemory defaults)
0.01user 0.00system 1:18.12elapsed 0%CPU (0avgtext+0avgdata 234240maxresident)k
0.00user 0.00system 1:15.48elapsed 0%CPU (0avgtext+0avgdata 234496maxresident)k
0.00user 0.00system 1:15.84elapsed 0%CPU (0avgtext+0avgdata 233984maxresident)k
-no_count_leaks
0.00user 0.00system 0:57.40elapsed 0%CPU (0avgtext+0avgdata 234240maxresident)k
0.00user 0.00system 0:57.03elapsed 0%CPU (0avgtext+0avgdata 234240maxresident)k
0.00user 0.00system 0:57.42elapsed 0%CPU (0avgtext+0avgdata 234240maxresident)k
-no_check_uninitialized
0.00user 0.00system 0:48.50elapsed 0%CPU (0avgtext+0avgdata 234496maxresident)k
0.00user 0.00system 0:45.48elapsed 0%CPU (0avgtext+0avgdata 234240maxresident)k
0.00user 0.00system 0:45.59elapsed 0%CPU (0avgtext+0avgdata 233984maxresident)k
-no_check_uninitialized -no_count_leaks
0.00user 0.00system 0:27.33elapsed 0%CPU (0avgtext+0avgdata 234240maxresident)k
0.00user 0.00system 0:27.06elapsed 0%CPU (0avgtext+0avgdata 234240maxresident)k
0.00user 0.00system 0:27.78elapsed 0%CPU (0avgtext+0avgdata 234240maxresident)k
-leaks_only
0.00user 0.00system 0:34.41elapsed 0%CPU (0avgtext+0avgdata 234240maxresident)k
0.00user 0.00system 0:34.38elapsed 0%CPU (0avgtext+0avgdata 233984maxresident)k
0.00user 0.00system 0:34.66elapsed 0%CPU (0avgtext+0avgdata 233984maxresident)k
-leaks_only -no_zero_stack
0.00user 0.00system 0:33.57elapsed 0%CPU (0avgtext+0avgdata 234240maxresident)k
0.00user 0.01system 0:33.54elapsed 0%CPU (0avgtext+0avgdata 234496maxresident)k
0.00user 0.00system 0:33.58elapsed 0%CPU (0avgtext+0avgdata 234496maxresident)k
-leaks_only -no_count_leaks
0.00user 0.00system 0:19.81elapsed 0%CPU (0avgtext+0avgdata 234240maxresident)k
0.00user 0.00system 0:17.76elapsed 0%CPU (0avgtext+0avgdata 234496maxresident)k
0.00user 0.00system 0:17.81elapsed 0%CPU (0avgtext+0avgdata 234240maxresident)k
-leaks_only -no_count_leaks -no_track_allocs
0.00user 0.00system 0:03.22elapsed 0%CPU (0avgtext+0avgdata 234240maxresident)k
0.00user 0.00system 0:03.27elapsed 0%CPU (0avgtext+0avgdata 234240maxresident)k
0.00user 0.01system 0:03.33elapsed 0%CPU (0avgtext+0avgdata 234240maxresident)k

=> rough split:
1.7 1.7 app
- 0.7 2.4 DR
- 0.9 3.3 drmem base client init, -code_api, etc.
- 15. 18.3 malloc interception
- 15. 33.6 callstack on every malloc
- 13. 45.6 addronly instru
- 30. 75.6 full instru

prior to my issue #460 improvements, malloc interception was 30s instead of 15s

so this issue tries to shrink the 15s from callstack walking

one thing that shows up led to DRi#635: provide faster dr_try_setup() that doesn't allocate memory

_Original issue: http://code.google.com/p/drmemory/issues/detail?id=711_