Philippe Waroquiers 352b1d384c Improves stacktrace unwinding on x86 ...

* other platforms (e.g. amd64) are first trying to unwind
  with cfi info, then with the fp chain.
* fp unwind when code is compiled without frame pointer can
  fail and give incomplete stack traces (often terminating
  with a random program counter, causing a huge amount of
  recorded stack traces).

This patch improves unwinding on x86 by:
* first time an IP is unwound, do the unwind both with
  CFI technique and with fp technique.
  If results are identical, IP is inserted in a cache of
  'fp unwindable' IP
* following unwind of the same IP are then done directly
  either with fp unwind or with cfi, depending on the
  cached result of the check done during first unwind.

The cache is needed so as to avoid as much as possible cfi unwind,
as this is significantly slower than fp unwind.



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13280

2013-01-30 23:18:11 +00:00

134 KiB

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